Merge branch 'driver-api' into doc/4.9
This short series convers device-drivers.tmpl into the RST format, splits
it up, and sets up the result under Documentation/driver-api/. For added
fun, I've taken one top-level file (hsi.txt) and folded it into the
document as a way of showing the direction I'm thinking I would like things
to go. There is plenty more of this sort of work that could be done, to
say the least - this is just a beginning!
The formatted results can be seen at:
http://static.lwn.net/kerneldoc/driver-api/index.html
As part of the long-term task to turn Documentation/ into less of a horror
movie, I'd like to collect documentation of the driver-specific API here.
Arguably gpu/ and the media API stuff should eventually move here, though
we can discuss the color of that particular shed some other day.
Meanwhile, I'd appreciate comments on the general idea.
This commit is contained in:
Jonathan Corbet
commit
fd5d2b832d
|
|
@ -6,7 +6,7 @@
|
|||
# To add a new book the only step required is to add the book to the
|
||||
# list of DOCBOOKS.
|
||||
|
||||
DOCBOOKS := z8530book.xml device-drivers.xml \
|
||||
DOCBOOKS := z8530book.xml \
|
||||
kernel-hacking.xml kernel-locking.xml deviceiobook.xml \
|
||||
writing_usb_driver.xml networking.xml \
|
||||
kernel-api.xml filesystems.xml lsm.xml usb.xml kgdb.xml \
|
||||
|
|
|
|||
|
|
@ -1,521 +0,0 @@
|
|||
<?xml version="1.0" encoding="UTF-8"?>
|
||||
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
|
||||
"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
|
||||
|
||||
<book id="LinuxDriversAPI">
|
||||
<bookinfo>
|
||||
<title>Linux Device Drivers</title>
|
||||
|
||||
<legalnotice>
|
||||
<para>
|
||||
This documentation is free software; you can redistribute
|
||||
it and/or modify it under the terms of the GNU General Public
|
||||
License as published by the Free Software Foundation; either
|
||||
version 2 of the License, or (at your option) any later
|
||||
version.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
This program is distributed in the hope that it will be
|
||||
useful, but WITHOUT ANY WARRANTY; without even the implied
|
||||
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
|
||||
See the GNU General Public License for more details.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
You should have received a copy of the GNU General Public
|
||||
License along with this program; if not, write to the Free
|
||||
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
|
||||
MA 02111-1307 USA
|
||||
</para>
|
||||
|
||||
<para>
|
||||
For more details see the file COPYING in the source
|
||||
distribution of Linux.
|
||||
</para>
|
||||
</legalnotice>
|
||||
</bookinfo>
|
||||
|
||||
<toc></toc>
|
||||
|
||||
<chapter id="Basics">
|
||||
<title>Driver Basics</title>
|
||||
<sect1><title>Driver Entry and Exit points</title>
|
||||
!Iinclude/linux/init.h
|
||||
</sect1>
|
||||
|
||||
<sect1><title>Atomic and pointer manipulation</title>
|
||||
!Iarch/x86/include/asm/atomic.h
|
||||
</sect1>
|
||||
|
||||
<sect1><title>Delaying, scheduling, and timer routines</title>
|
||||
!Iinclude/linux/sched.h
|
||||
!Ekernel/sched/core.c
|
||||
!Ikernel/sched/cpupri.c
|
||||
!Ikernel/sched/fair.c
|
||||
!Iinclude/linux/completion.h
|
||||
!Ekernel/time/timer.c
|
||||
</sect1>
|
||||
<sect1><title>Wait queues and Wake events</title>
|
||||
!Iinclude/linux/wait.h
|
||||
!Ekernel/sched/wait.c
|
||||
</sect1>
|
||||
<sect1><title>High-resolution timers</title>
|
||||
!Iinclude/linux/ktime.h
|
||||
!Iinclude/linux/hrtimer.h
|
||||
!Ekernel/time/hrtimer.c
|
||||
</sect1>
|
||||
<sect1><title>Workqueues and Kevents</title>
|
||||
!Iinclude/linux/workqueue.h
|
||||
!Ekernel/workqueue.c
|
||||
</sect1>
|
||||
<sect1><title>Internal Functions</title>
|
||||
!Ikernel/exit.c
|
||||
!Ikernel/signal.c
|
||||
!Iinclude/linux/kthread.h
|
||||
!Ekernel/kthread.c
|
||||
</sect1>
|
||||
|
||||
<sect1><title>Kernel objects manipulation</title>
|
||||
<!--
|
||||
X!Iinclude/linux/kobject.h
|
||||
-->
|
||||
!Elib/kobject.c
|
||||
</sect1>
|
||||
|
||||
<sect1><title>Kernel utility functions</title>
|
||||
!Iinclude/linux/kernel.h
|
||||
!Ekernel/printk/printk.c
|
||||
!Ekernel/panic.c
|
||||
!Ekernel/sys.c
|
||||
!Ekernel/rcu/srcu.c
|
||||
!Ekernel/rcu/tree.c
|
||||
!Ekernel/rcu/tree_plugin.h
|
||||
!Ekernel/rcu/update.c
|
||||
</sect1>
|
||||
|
||||
<sect1><title>Device Resource Management</title>
|
||||
!Edrivers/base/devres.c
|
||||
</sect1>
|
||||
|
||||
</chapter>
|
||||
|
||||
<chapter id="devdrivers">
|
||||
<title>Device drivers infrastructure</title>
|
||||
<sect1><title>The Basic Device Driver-Model Structures </title>
|
||||
!Iinclude/linux/device.h
|
||||
</sect1>
|
||||
<sect1><title>Device Drivers Base</title>
|
||||
!Idrivers/base/init.c
|
||||
!Edrivers/base/driver.c
|
||||
!Edrivers/base/core.c
|
||||
!Edrivers/base/syscore.c
|
||||
!Edrivers/base/class.c
|
||||
!Idrivers/base/node.c
|
||||
!Edrivers/base/firmware_class.c
|
||||
!Edrivers/base/transport_class.c
|
||||
<!-- Cannot be included, because
|
||||
attribute_container_add_class_device_adapter
|
||||
and attribute_container_classdev_to_container
|
||||
exceed allowed 44 characters maximum
|
||||
X!Edrivers/base/attribute_container.c
|
||||
-->
|
||||
!Edrivers/base/dd.c
|
||||
<!--
|
||||
X!Edrivers/base/interface.c
|
||||
-->
|
||||
!Iinclude/linux/platform_device.h
|
||||
!Edrivers/base/platform.c
|
||||
!Edrivers/base/bus.c
|
||||
</sect1>
|
||||
<sect1>
|
||||
<title>Buffer Sharing and Synchronization</title>
|
||||
<para>
|
||||
The dma-buf subsystem provides the framework for sharing buffers
|
||||
for hardware (DMA) access across multiple device drivers and
|
||||
subsystems, and for synchronizing asynchronous hardware access.
|
||||
</para>
|
||||
<para>
|
||||
This is used, for example, by drm "prime" multi-GPU support, but
|
||||
is of course not limited to GPU use cases.
|
||||
</para>
|
||||
<para>
|
||||
The three main components of this are: (1) dma-buf, representing
|
||||
a sg_table and exposed to userspace as a file descriptor to allow
|
||||
passing between devices, (2) fence, which provides a mechanism
|
||||
to signal when one device as finished access, and (3) reservation,
|
||||
which manages the shared or exclusive fence(s) associated with
|
||||
the buffer.
|
||||
</para>
|
||||
<sect2><title>dma-buf</title>
|
||||
!Edrivers/dma-buf/dma-buf.c
|
||||
!Iinclude/linux/dma-buf.h
|
||||
</sect2>
|
||||
<sect2><title>reservation</title>
|
||||
!Pdrivers/dma-buf/reservation.c Reservation Object Overview
|
||||
!Edrivers/dma-buf/reservation.c
|
||||
!Iinclude/linux/reservation.h
|
||||
</sect2>
|
||||
<sect2><title>fence</title>
|
||||
!Edrivers/dma-buf/fence.c
|
||||
!Iinclude/linux/fence.h
|
||||
!Edrivers/dma-buf/seqno-fence.c
|
||||
!Iinclude/linux/seqno-fence.h
|
||||
!Edrivers/dma-buf/fence-array.c
|
||||
!Iinclude/linux/fence-array.h
|
||||
!Edrivers/dma-buf/reservation.c
|
||||
!Iinclude/linux/reservation.h
|
||||
!Edrivers/dma-buf/sync_file.c
|
||||
!Iinclude/linux/sync_file.h
|
||||
</sect2>
|
||||
</sect1>
|
||||
<sect1><title>Device Drivers DMA Management</title>
|
||||
!Edrivers/base/dma-coherent.c
|
||||
!Edrivers/base/dma-mapping.c
|
||||
</sect1>
|
||||
<sect1><title>Device Drivers Power Management</title>
|
||||
!Edrivers/base/power/main.c
|
||||
</sect1>
|
||||
<sect1><title>Device Drivers ACPI Support</title>
|
||||
<!-- Internal functions only
|
||||
X!Edrivers/acpi/sleep/main.c
|
||||
X!Edrivers/acpi/sleep/wakeup.c
|
||||
X!Edrivers/acpi/motherboard.c
|
||||
X!Edrivers/acpi/bus.c
|
||||
-->
|
||||
!Edrivers/acpi/scan.c
|
||||
!Idrivers/acpi/scan.c
|
||||
<!-- No correct structured comments
|
||||
X!Edrivers/acpi/pci_bind.c
|
||||
-->
|
||||
</sect1>
|
||||
<sect1><title>Device drivers PnP support</title>
|
||||
!Idrivers/pnp/core.c
|
||||
<!-- No correct structured comments
|
||||
X!Edrivers/pnp/system.c
|
||||
-->
|
||||
!Edrivers/pnp/card.c
|
||||
!Idrivers/pnp/driver.c
|
||||
!Edrivers/pnp/manager.c
|
||||
!Edrivers/pnp/support.c
|
||||
</sect1>
|
||||
<sect1><title>Userspace IO devices</title>
|
||||
!Edrivers/uio/uio.c
|
||||
!Iinclude/linux/uio_driver.h
|
||||
</sect1>
|
||||
</chapter>
|
||||
|
||||
<chapter id="parportdev">
|
||||
<title>Parallel Port Devices</title>
|
||||
!Iinclude/linux/parport.h
|
||||
!Edrivers/parport/ieee1284.c
|
||||
!Edrivers/parport/share.c
|
||||
!Idrivers/parport/daisy.c
|
||||
</chapter>
|
||||
|
||||
<chapter id="message_devices">
|
||||
<title>Message-based devices</title>
|
||||
<sect1><title>Fusion message devices</title>
|
||||
!Edrivers/message/fusion/mptbase.c
|
||||
!Idrivers/message/fusion/mptbase.c
|
||||
!Edrivers/message/fusion/mptscsih.c
|
||||
!Idrivers/message/fusion/mptscsih.c
|
||||
!Idrivers/message/fusion/mptctl.c
|
||||
!Idrivers/message/fusion/mptspi.c
|
||||
!Idrivers/message/fusion/mptfc.c
|
||||
!Idrivers/message/fusion/mptlan.c
|
||||
</sect1>
|
||||
</chapter>
|
||||
|
||||
<chapter id="snddev">
|
||||
<title>Sound Devices</title>
|
||||
!Iinclude/sound/core.h
|
||||
!Esound/sound_core.c
|
||||
!Iinclude/sound/pcm.h
|
||||
!Esound/core/pcm.c
|
||||
!Esound/core/device.c
|
||||
!Esound/core/info.c
|
||||
!Esound/core/rawmidi.c
|
||||
!Esound/core/sound.c
|
||||
!Esound/core/memory.c
|
||||
!Esound/core/pcm_memory.c
|
||||
!Esound/core/init.c
|
||||
!Esound/core/isadma.c
|
||||
!Esound/core/control.c
|
||||
!Esound/core/pcm_lib.c
|
||||
!Esound/core/hwdep.c
|
||||
!Esound/core/pcm_native.c
|
||||
!Esound/core/memalloc.c
|
||||
<!-- FIXME: Removed for now since no structured comments in source
|
||||
X!Isound/sound_firmware.c
|
||||
-->
|
||||
</chapter>
|
||||
|
||||
|
||||
<chapter id="uart16x50">
|
||||
<title>16x50 UART Driver</title>
|
||||
!Edrivers/tty/serial/serial_core.c
|
||||
!Edrivers/tty/serial/8250/8250_core.c
|
||||
</chapter>
|
||||
|
||||
<chapter id="fbdev">
|
||||
<title>Frame Buffer Library</title>
|
||||
|
||||
<para>
|
||||
The frame buffer drivers depend heavily on four data structures.
|
||||
These structures are declared in include/linux/fb.h. They are
|
||||
fb_info, fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs.
|
||||
The last three can be made available to and from userland.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
fb_info defines the current state of a particular video card.
|
||||
Inside fb_info, there exists a fb_ops structure which is a
|
||||
collection of needed functions to make fbdev and fbcon work.
|
||||
fb_info is only visible to the kernel.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
fb_var_screeninfo is used to describe the features of a video card
|
||||
that are user defined. With fb_var_screeninfo, things such as
|
||||
depth and the resolution may be defined.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The next structure is fb_fix_screeninfo. This defines the
|
||||
properties of a card that are created when a mode is set and can't
|
||||
be changed otherwise. A good example of this is the start of the
|
||||
frame buffer memory. This "locks" the address of the frame buffer
|
||||
memory, so that it cannot be changed or moved.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The last structure is fb_monospecs. In the old API, there was
|
||||
little importance for fb_monospecs. This allowed for forbidden things
|
||||
such as setting a mode of 800x600 on a fix frequency monitor. With
|
||||
the new API, fb_monospecs prevents such things, and if used
|
||||
correctly, can prevent a monitor from being cooked. fb_monospecs
|
||||
will not be useful until kernels 2.5.x.
|
||||
</para>
|
||||
|
||||
<sect1><title>Frame Buffer Memory</title>
|
||||
!Edrivers/video/fbdev/core/fbmem.c
|
||||
</sect1>
|
||||
<!--
|
||||
<sect1><title>Frame Buffer Console</title>
|
||||
X!Edrivers/video/console/fbcon.c
|
||||
</sect1>
|
||||
-->
|
||||
<sect1><title>Frame Buffer Colormap</title>
|
||||
!Edrivers/video/fbdev/core/fbcmap.c
|
||||
</sect1>
|
||||
<!-- FIXME:
|
||||
drivers/video/fbgen.c has no docs, which stuffs up the sgml. Comment
|
||||
out until somebody adds docs. KAO
|
||||
<sect1><title>Frame Buffer Generic Functions</title>
|
||||
X!Idrivers/video/fbgen.c
|
||||
</sect1>
|
||||
KAO -->
|
||||
<sect1><title>Frame Buffer Video Mode Database</title>
|
||||
!Idrivers/video/fbdev/core/modedb.c
|
||||
!Edrivers/video/fbdev/core/modedb.c
|
||||
</sect1>
|
||||
<sect1><title>Frame Buffer Macintosh Video Mode Database</title>
|
||||
!Edrivers/video/fbdev/macmodes.c
|
||||
</sect1>
|
||||
<sect1><title>Frame Buffer Fonts</title>
|
||||
<para>
|
||||
Refer to the file lib/fonts/fonts.c for more information.
|
||||
</para>
|
||||
<!-- FIXME: Removed for now since no structured comments in source
|
||||
X!Ilib/fonts/fonts.c
|
||||
-->
|
||||
</sect1>
|
||||
</chapter>
|
||||
|
||||
<chapter id="input_subsystem">
|
||||
<title>Input Subsystem</title>
|
||||
<sect1><title>Input core</title>
|
||||
!Iinclude/linux/input.h
|
||||
!Edrivers/input/input.c
|
||||
!Edrivers/input/ff-core.c
|
||||
!Edrivers/input/ff-memless.c
|
||||
</sect1>
|
||||
<sect1><title>Multitouch Library</title>
|
||||
!Iinclude/linux/input/mt.h
|
||||
!Edrivers/input/input-mt.c
|
||||
</sect1>
|
||||
<sect1><title>Polled input devices</title>
|
||||
!Iinclude/linux/input-polldev.h
|
||||
!Edrivers/input/input-polldev.c
|
||||
</sect1>
|
||||
<sect1><title>Matrix keyboards/keypads</title>
|
||||
!Iinclude/linux/input/matrix_keypad.h
|
||||
</sect1>
|
||||
<sect1><title>Sparse keymap support</title>
|
||||
!Iinclude/linux/input/sparse-keymap.h
|
||||
!Edrivers/input/sparse-keymap.c
|
||||
</sect1>
|
||||
</chapter>
|
||||
|
||||
<chapter id="spi">
|
||||
<title>Serial Peripheral Interface (SPI)</title>
|
||||
<para>
|
||||
SPI is the "Serial Peripheral Interface", widely used with
|
||||
embedded systems because it is a simple and efficient
|
||||
interface: basically a multiplexed shift register.
|
||||
Its three signal wires hold a clock (SCK, often in the range
|
||||
of 1-20 MHz), a "Master Out, Slave In" (MOSI) data line, and
|
||||
a "Master In, Slave Out" (MISO) data line.
|
||||
SPI is a full duplex protocol; for each bit shifted out the
|
||||
MOSI line (one per clock) another is shifted in on the MISO line.
|
||||
Those bits are assembled into words of various sizes on the
|
||||
way to and from system memory.
|
||||
An additional chipselect line is usually active-low (nCS);
|
||||
four signals are normally used for each peripheral, plus
|
||||
sometimes an interrupt.
|
||||
</para>
|
||||
<para>
|
||||
The SPI bus facilities listed here provide a generalized
|
||||
interface to declare SPI busses and devices, manage them
|
||||
according to the standard Linux driver model, and perform
|
||||
input/output operations.
|
||||
At this time, only "master" side interfaces are supported,
|
||||
where Linux talks to SPI peripherals and does not implement
|
||||
such a peripheral itself.
|
||||
(Interfaces to support implementing SPI slaves would
|
||||
necessarily look different.)
|
||||
</para>
|
||||
<para>
|
||||
The programming interface is structured around two kinds of driver,
|
||||
and two kinds of device.
|
||||
A "Controller Driver" abstracts the controller hardware, which may
|
||||
be as simple as a set of GPIO pins or as complex as a pair of FIFOs
|
||||
connected to dual DMA engines on the other side of the SPI shift
|
||||
register (maximizing throughput). Such drivers bridge between
|
||||
whatever bus they sit on (often the platform bus) and SPI, and
|
||||
expose the SPI side of their device as a
|
||||
<structname>struct spi_master</structname>.
|
||||
SPI devices are children of that master, represented as a
|
||||
<structname>struct spi_device</structname> and manufactured from
|
||||
<structname>struct spi_board_info</structname> descriptors which
|
||||
are usually provided by board-specific initialization code.
|
||||
A <structname>struct spi_driver</structname> is called a
|
||||
"Protocol Driver", and is bound to a spi_device using normal
|
||||
driver model calls.
|
||||
</para>
|
||||
<para>
|
||||
The I/O model is a set of queued messages. Protocol drivers
|
||||
submit one or more <structname>struct spi_message</structname>
|
||||
objects, which are processed and completed asynchronously.
|
||||
(There are synchronous wrappers, however.) Messages are
|
||||
built from one or more <structname>struct spi_transfer</structname>
|
||||
objects, each of which wraps a full duplex SPI transfer.
|
||||
A variety of protocol tweaking options are needed, because
|
||||
different chips adopt very different policies for how they
|
||||
use the bits transferred with SPI.
|
||||
</para>
|
||||
!Iinclude/linux/spi/spi.h
|
||||
!Fdrivers/spi/spi.c spi_register_board_info
|
||||
!Edrivers/spi/spi.c
|
||||
</chapter>
|
||||
|
||||
<chapter id="i2c">
|
||||
<title>I<superscript>2</superscript>C and SMBus Subsystem</title>
|
||||
|
||||
<para>
|
||||
I<superscript>2</superscript>C (or without fancy typography, "I2C")
|
||||
is an acronym for the "Inter-IC" bus, a simple bus protocol which is
|
||||
widely used where low data rate communications suffice.
|
||||
Since it's also a licensed trademark, some vendors use another
|
||||
name (such as "Two-Wire Interface", TWI) for the same bus.
|
||||
I2C only needs two signals (SCL for clock, SDA for data), conserving
|
||||
board real estate and minimizing signal quality issues.
|
||||
Most I2C devices use seven bit addresses, and bus speeds of up
|
||||
to 400 kHz; there's a high speed extension (3.4 MHz) that's not yet
|
||||
found wide use.
|
||||
I2C is a multi-master bus; open drain signaling is used to
|
||||
arbitrate between masters, as well as to handshake and to
|
||||
synchronize clocks from slower clients.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The Linux I2C programming interfaces support only the master
|
||||
side of bus interactions, not the slave side.
|
||||
The programming interface is structured around two kinds of driver,
|
||||
and two kinds of device.
|
||||
An I2C "Adapter Driver" abstracts the controller hardware; it binds
|
||||
to a physical device (perhaps a PCI device or platform_device) and
|
||||
exposes a <structname>struct i2c_adapter</structname> representing
|
||||
each I2C bus segment it manages.
|
||||
On each I2C bus segment will be I2C devices represented by a
|
||||
<structname>struct i2c_client</structname>. Those devices will
|
||||
be bound to a <structname>struct i2c_driver</structname>,
|
||||
which should follow the standard Linux driver model.
|
||||
(At this writing, a legacy model is more widely used.)
|
||||
There are functions to perform various I2C protocol operations; at
|
||||
this writing all such functions are usable only from task context.
|
||||
</para>
|
||||
|
||||
<para>
|
||||
The System Management Bus (SMBus) is a sibling protocol. Most SMBus
|
||||
systems are also I2C conformant. The electrical constraints are
|
||||
tighter for SMBus, and it standardizes particular protocol messages
|
||||
and idioms. Controllers that support I2C can also support most
|
||||
SMBus operations, but SMBus controllers don't support all the protocol
|
||||
options that an I2C controller will.
|
||||
There are functions to perform various SMBus protocol operations,
|
||||
either using I2C primitives or by issuing SMBus commands to
|
||||
i2c_adapter devices which don't support those I2C operations.
|
||||
</para>
|
||||
|
||||
!Iinclude/linux/i2c.h
|
||||
!Fdrivers/i2c/i2c-boardinfo.c i2c_register_board_info
|
||||
!Edrivers/i2c/i2c-core.c
|
||||
</chapter>
|
||||
|
||||
<chapter id="hsi">
|
||||
<title>High Speed Synchronous Serial Interface (HSI)</title>
|
||||
|
||||
<para>
|
||||
High Speed Synchronous Serial Interface (HSI) is a
|
||||
serial interface mainly used for connecting application
|
||||
engines (APE) with cellular modem engines (CMT) in cellular
|
||||
handsets.
|
||||
|
||||
HSI provides multiplexing for up to 16 logical channels,
|
||||
low-latency and full duplex communication.
|
||||
</para>
|
||||
|
||||
!Iinclude/linux/hsi/hsi.h
|
||||
!Edrivers/hsi/hsi_core.c
|
||||
</chapter>
|
||||
|
||||
<chapter id="pwm">
|
||||
<title>Pulse-Width Modulation (PWM)</title>
|
||||
<para>
|
||||
Pulse-width modulation is a modulation technique primarily used to
|
||||
control power supplied to electrical devices.
|
||||
</para>
|
||||
<para>
|
||||
The PWM framework provides an abstraction for providers and consumers
|
||||
of PWM signals. A controller that provides one or more PWM signals is
|
||||
registered as <structname>struct pwm_chip</structname>. Providers are
|
||||
expected to embed this structure in a driver-specific structure. This
|
||||
structure contains fields that describe a particular chip.
|
||||
</para>
|
||||
<para>
|
||||
A chip exposes one or more PWM signal sources, each of which exposed
|
||||
as a <structname>struct pwm_device</structname>. Operations can be
|
||||
performed on PWM devices to control the period, duty cycle, polarity
|
||||
and active state of the signal.
|
||||
</para>
|
||||
<para>
|
||||
Note that PWM devices are exclusive resources: they can always only be
|
||||
used by one consumer at a time.
|
||||
</para>
|
||||
!Iinclude/linux/pwm.h
|
||||
!Edrivers/pwm/core.c
|
||||
</chapter>
|
||||
|
||||
</book>
|
||||
|
|
@ -0,0 +1,120 @@
|
|||
Driver Basics
|
||||
=============
|
||||
|
||||
Driver Entry and Exit points
|
||||
----------------------------
|
||||
|
||||
.. kernel-doc:: include/linux/init.h
|
||||
:internal:
|
||||
|
||||
Atomic and pointer manipulation
|
||||
-------------------------------
|
||||
|
||||
.. kernel-doc:: arch/x86/include/asm/atomic.h
|
||||
:internal:
|
||||
|
||||
Delaying, scheduling, and timer routines
|
||||
----------------------------------------
|
||||
|
||||
.. kernel-doc:: include/linux/sched.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: kernel/sched/core.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: kernel/sched/cpupri.c
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: kernel/sched/fair.c
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: include/linux/completion.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: kernel/time/timer.c
|
||||
:export:
|
||||
|
||||
Wait queues and Wake events
|
||||
---------------------------
|
||||
|
||||
.. kernel-doc:: include/linux/wait.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: kernel/sched/wait.c
|
||||
:export:
|
||||
|
||||
High-resolution timers
|
||||
----------------------
|
||||
|
||||
.. kernel-doc:: include/linux/ktime.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: include/linux/hrtimer.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: kernel/time/hrtimer.c
|
||||
:export:
|
||||
|
||||
Workqueues and Kevents
|
||||
----------------------
|
||||
|
||||
.. kernel-doc:: include/linux/workqueue.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: kernel/workqueue.c
|
||||
:export:
|
||||
|
||||
Internal Functions
|
||||
------------------
|
||||
|
||||
.. kernel-doc:: kernel/exit.c
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: kernel/signal.c
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: include/linux/kthread.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: kernel/kthread.c
|
||||
:export:
|
||||
|
||||
Kernel objects manipulation
|
||||
---------------------------
|
||||
|
||||
.. kernel-doc:: lib/kobject.c
|
||||
:export:
|
||||
|
||||
Kernel utility functions
|
||||
------------------------
|
||||
|
||||
.. kernel-doc:: include/linux/kernel.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: kernel/printk/printk.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: kernel/panic.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: kernel/sys.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: kernel/rcu/srcu.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: kernel/rcu/tree.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: kernel/rcu/tree_plugin.h
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: kernel/rcu/update.c
|
||||
:export:
|
||||
|
||||
Device Resource Management
|
||||
--------------------------
|
||||
|
||||
.. kernel-doc:: drivers/base/devres.c
|
||||
:export:
|
||||
|
||||
|
|
@ -0,0 +1,62 @@
|
|||
Frame Buffer Library
|
||||
====================
|
||||
|
||||
The frame buffer drivers depend heavily on four data structures. These
|
||||
structures are declared in include/linux/fb.h. They are fb_info,
|
||||
fb_var_screeninfo, fb_fix_screeninfo and fb_monospecs. The last
|
||||
three can be made available to and from userland.
|
||||
|
||||
fb_info defines the current state of a particular video card. Inside
|
||||
fb_info, there exists a fb_ops structure which is a collection of
|
||||
needed functions to make fbdev and fbcon work. fb_info is only visible
|
||||
to the kernel.
|
||||
|
||||
fb_var_screeninfo is used to describe the features of a video card
|
||||
that are user defined. With fb_var_screeninfo, things such as depth
|
||||
and the resolution may be defined.
|
||||
|
||||
The next structure is fb_fix_screeninfo. This defines the properties
|
||||
of a card that are created when a mode is set and can't be changed
|
||||
otherwise. A good example of this is the start of the frame buffer
|
||||
memory. This "locks" the address of the frame buffer memory, so that it
|
||||
cannot be changed or moved.
|
||||
|
||||
The last structure is fb_monospecs. In the old API, there was little
|
||||
importance for fb_monospecs. This allowed for forbidden things such as
|
||||
setting a mode of 800x600 on a fix frequency monitor. With the new API,
|
||||
fb_monospecs prevents such things, and if used correctly, can prevent a
|
||||
monitor from being cooked. fb_monospecs will not be useful until
|
||||
kernels 2.5.x.
|
||||
|
||||
Frame Buffer Memory
|
||||
-------------------
|
||||
|
||||
.. kernel-doc:: drivers/video/fbdev/core/fbmem.c
|
||||
:export:
|
||||
|
||||
Frame Buffer Colormap
|
||||
---------------------
|
||||
|
||||
.. kernel-doc:: drivers/video/fbdev/core/fbcmap.c
|
||||
:export:
|
||||
|
||||
Frame Buffer Video Mode Database
|
||||
--------------------------------
|
||||
|
||||
.. kernel-doc:: drivers/video/fbdev/core/modedb.c
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/video/fbdev/core/modedb.c
|
||||
:export:
|
||||
|
||||
Frame Buffer Macintosh Video Mode Database
|
||||
------------------------------------------
|
||||
|
||||
.. kernel-doc:: drivers/video/fbdev/macmodes.c
|
||||
:export:
|
||||
|
||||
Frame Buffer Fonts
|
||||
------------------
|
||||
|
||||
Refer to the file lib/fonts/fonts.c for more information.
|
||||
|
||||
|
|
@ -0,0 +1,88 @@
|
|||
High Speed Synchronous Serial Interface (HSI)
|
||||
=============================================
|
||||
|
||||
Introduction
|
||||
---------------
|
||||
|
||||
High Speed Syncronous Interface (HSI) is a fullduplex, low latency protocol,
|
||||
that is optimized for die-level interconnect between an Application Processor
|
||||
and a Baseband chipset. It has been specified by the MIPI alliance in 2003 and
|
||||
implemented by multiple vendors since then.
|
||||
|
||||
The HSI interface supports full duplex communication over multiple channels
|
||||
(typically 8) and is capable of reaching speeds up to 200 Mbit/s.
|
||||
|
||||
The serial protocol uses two signals, DATA and FLAG as combined data and clock
|
||||
signals and an additional READY signal for flow control. An additional WAKE
|
||||
signal can be used to wakeup the chips from standby modes. The signals are
|
||||
commonly prefixed by AC for signals going from the application die to the
|
||||
cellular die and CA for signals going the other way around.
|
||||
|
||||
::
|
||||
|
||||
+------------+ +---------------+
|
||||
| Cellular | | Application |
|
||||
| Die | | Die |
|
||||
| | - - - - - - CAWAKE - - - - - - >| |
|
||||
| T|------------ CADATA ------------>|R |
|
||||
| X|------------ CAFLAG ------------>|X |
|
||||
| |<----------- ACREADY ------------| |
|
||||
| | | |
|
||||
| | | |
|
||||
| |< - - - - - ACWAKE - - - - - - -| |
|
||||
| R|<----------- ACDATA -------------|T |
|
||||
| X|<----------- ACFLAG -------------|X |
|
||||
| |------------ CAREADY ----------->| |
|
||||
| | | |
|
||||
| | | |
|
||||
+------------+ +---------------+
|
||||
|
||||
HSI Subsystem in Linux
|
||||
-------------------------
|
||||
|
||||
In the Linux kernel the hsi subsystem is supposed to be used for HSI devices.
|
||||
The hsi subsystem contains drivers for hsi controllers including support for
|
||||
multi-port controllers and provides a generic API for using the HSI ports.
|
||||
|
||||
It also contains HSI client drivers, which make use of the generic API to
|
||||
implement a protocol used on the HSI interface. These client drivers can
|
||||
use an arbitrary number of channels.
|
||||
|
||||
hsi-char Device
|
||||
------------------
|
||||
|
||||
Each port automatically registers a generic client driver called hsi_char,
|
||||
which provides a charecter device for userspace representing the HSI port.
|
||||
It can be used to communicate via HSI from userspace. Userspace may
|
||||
configure the hsi_char device using the following ioctl commands:
|
||||
|
||||
HSC_RESET
|
||||
flush the HSI port
|
||||
|
||||
HSC_SET_PM
|
||||
enable or disable the client.
|
||||
|
||||
HSC_SEND_BREAK
|
||||
send break
|
||||
|
||||
HSC_SET_RX
|
||||
set RX configuration
|
||||
|
||||
HSC_GET_RX
|
||||
get RX configuration
|
||||
|
||||
HSC_SET_TX
|
||||
set TX configuration
|
||||
|
||||
HSC_GET_TX
|
||||
get TX configuration
|
||||
|
||||
The kernel HSI API
|
||||
------------------
|
||||
|
||||
.. kernel-doc:: include/linux/hsi/hsi.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/hsi/hsi_core.c
|
||||
:export:
|
||||
|
||||
|
|
@ -0,0 +1,46 @@
|
|||
I\ :sup:`2`\ C and SMBus Subsystem
|
||||
==================================
|
||||
|
||||
I\ :sup:`2`\ C (or without fancy typography, "I2C") is an acronym for
|
||||
the "Inter-IC" bus, a simple bus protocol which is widely used where low
|
||||
data rate communications suffice. Since it's also a licensed trademark,
|
||||
some vendors use another name (such as "Two-Wire Interface", TWI) for
|
||||
the same bus. I2C only needs two signals (SCL for clock, SDA for data),
|
||||
conserving board real estate and minimizing signal quality issues. Most
|
||||
I2C devices use seven bit addresses, and bus speeds of up to 400 kHz;
|
||||
there's a high speed extension (3.4 MHz) that's not yet found wide use.
|
||||
I2C is a multi-master bus; open drain signaling is used to arbitrate
|
||||
between masters, as well as to handshake and to synchronize clocks from
|
||||
slower clients.
|
||||
|
||||
The Linux I2C programming interfaces support only the master side of bus
|
||||
interactions, not the slave side. The programming interface is
|
||||
structured around two kinds of driver, and two kinds of device. An I2C
|
||||
"Adapter Driver" abstracts the controller hardware; it binds to a
|
||||
physical device (perhaps a PCI device or platform_device) and exposes a
|
||||
:c:type:`struct i2c_adapter <i2c_adapter>` representing each
|
||||
I2C bus segment it manages. On each I2C bus segment will be I2C devices
|
||||
represented by a :c:type:`struct i2c_client <i2c_client>`.
|
||||
Those devices will be bound to a :c:type:`struct i2c_driver
|
||||
<i2c_driver>`, which should follow the standard Linux driver
|
||||
model. (At this writing, a legacy model is more widely used.) There are
|
||||
functions to perform various I2C protocol operations; at this writing
|
||||
all such functions are usable only from task context.
|
||||
|
||||
The System Management Bus (SMBus) is a sibling protocol. Most SMBus
|
||||
systems are also I2C conformant. The electrical constraints are tighter
|
||||
for SMBus, and it standardizes particular protocol messages and idioms.
|
||||
Controllers that support I2C can also support most SMBus operations, but
|
||||
SMBus controllers don't support all the protocol options that an I2C
|
||||
controller will. There are functions to perform various SMBus protocol
|
||||
operations, either using I2C primitives or by issuing SMBus commands to
|
||||
i2c_adapter devices which don't support those I2C operations.
|
||||
|
||||
.. kernel-doc:: include/linux/i2c.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/i2c/i2c-boardinfo.c
|
||||
:functions: i2c_register_board_info
|
||||
|
||||
.. kernel-doc:: drivers/i2c/i2c-core.c
|
||||
:export:
|
||||
|
|
@ -0,0 +1,26 @@
|
|||
========================================
|
||||
The Linux driver implementer's API guide
|
||||
========================================
|
||||
|
||||
The kernel offers a wide variety of interfaces to support the development
|
||||
of device drivers. This document is an only somewhat organized collection
|
||||
of some of those interfaces — it will hopefully get better over time! The
|
||||
available subsections can be seen below.
|
||||
|
||||
.. class:: toc-title
|
||||
|
||||
Table of contents
|
||||
|
||||
.. toctree::
|
||||
:maxdepth: 2
|
||||
|
||||
basics
|
||||
infrastructure
|
||||
message-based
|
||||
sound
|
||||
frame-buffer
|
||||
input
|
||||
spi
|
||||
i2c
|
||||
hsi
|
||||
miscellaneous
|
||||
|
|
@ -0,0 +1,169 @@
|
|||
Device drivers infrastructure
|
||||
=============================
|
||||
|
||||
The Basic Device Driver-Model Structures
|
||||
----------------------------------------
|
||||
|
||||
.. kernel-doc:: include/linux/device.h
|
||||
:internal:
|
||||
|
||||
Device Drivers Base
|
||||
-------------------
|
||||
|
||||
.. kernel-doc:: drivers/base/init.c
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/base/driver.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/base/core.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/base/syscore.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/base/class.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/base/node.c
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/base/firmware_class.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/base/transport_class.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/base/dd.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: include/linux/platform_device.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/base/platform.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/base/bus.c
|
||||
:export:
|
||||
|
||||
Buffer Sharing and Synchronization
|
||||
----------------------------------
|
||||
|
||||
The dma-buf subsystem provides the framework for sharing buffers for
|
||||
hardware (DMA) access across multiple device drivers and subsystems, and
|
||||
for synchronizing asynchronous hardware access.
|
||||
|
||||
This is used, for example, by drm "prime" multi-GPU support, but is of
|
||||
course not limited to GPU use cases.
|
||||
|
||||
The three main components of this are: (1) dma-buf, representing a
|
||||
sg_table and exposed to userspace as a file descriptor to allow passing
|
||||
between devices, (2) fence, which provides a mechanism to signal when
|
||||
one device as finished access, and (3) reservation, which manages the
|
||||
shared or exclusive fence(s) associated with the buffer.
|
||||
|
||||
dma-buf
|
||||
~~~~~~~
|
||||
|
||||
.. kernel-doc:: drivers/dma-buf/dma-buf.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: include/linux/dma-buf.h
|
||||
:internal:
|
||||
|
||||
reservation
|
||||
~~~~~~~~~~~
|
||||
|
||||
.. kernel-doc:: drivers/dma-buf/reservation.c
|
||||
:doc: Reservation Object Overview
|
||||
|
||||
.. kernel-doc:: drivers/dma-buf/reservation.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: include/linux/reservation.h
|
||||
:internal:
|
||||
|
||||
fence
|
||||
~~~~~
|
||||
|
||||
.. kernel-doc:: drivers/dma-buf/fence.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: include/linux/fence.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/dma-buf/seqno-fence.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: include/linux/seqno-fence.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/dma-buf/fence-array.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: include/linux/fence-array.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/dma-buf/reservation.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: include/linux/reservation.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/dma-buf/sync_file.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: include/linux/sync_file.h
|
||||
:internal:
|
||||
|
||||
Device Drivers DMA Management
|
||||
-----------------------------
|
||||
|
||||
.. kernel-doc:: drivers/base/dma-coherent.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/base/dma-mapping.c
|
||||
:export:
|
||||
|
||||
Device Drivers Power Management
|
||||
-------------------------------
|
||||
|
||||
.. kernel-doc:: drivers/base/power/main.c
|
||||
:export:
|
||||
|
||||
Device Drivers ACPI Support
|
||||
---------------------------
|
||||
|
||||
.. kernel-doc:: drivers/acpi/scan.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/acpi/scan.c
|
||||
:internal:
|
||||
|
||||
Device drivers PnP support
|
||||
--------------------------
|
||||
|
||||
.. kernel-doc:: drivers/pnp/core.c
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/pnp/card.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/pnp/driver.c
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/pnp/manager.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/pnp/support.c
|
||||
:export:
|
||||
|
||||
Userspace IO devices
|
||||
--------------------
|
||||
|
||||
.. kernel-doc:: drivers/uio/uio.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: include/linux/uio_driver.h
|
||||
:internal:
|
||||
|
||||
|
|
@ -0,0 +1,51 @@
|
|||
Input Subsystem
|
||||
===============
|
||||
|
||||
Input core
|
||||
----------
|
||||
|
||||
.. kernel-doc:: include/linux/input.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/input/input.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/input/ff-core.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/input/ff-memless.c
|
||||
:export:
|
||||
|
||||
Multitouch Library
|
||||
------------------
|
||||
|
||||
.. kernel-doc:: include/linux/input/mt.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/input/input-mt.c
|
||||
:export:
|
||||
|
||||
Polled input devices
|
||||
--------------------
|
||||
|
||||
.. kernel-doc:: include/linux/input-polldev.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/input/input-polldev.c
|
||||
:export:
|
||||
|
||||
Matrix keyboards/keypads
|
||||
------------------------
|
||||
|
||||
.. kernel-doc:: include/linux/input/matrix_keypad.h
|
||||
:internal:
|
||||
|
||||
Sparse keymap support
|
||||
---------------------
|
||||
|
||||
.. kernel-doc:: include/linux/input/sparse-keymap.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/input/sparse-keymap.c
|
||||
:export:
|
||||
|
||||
|
|
@ -0,0 +1,12 @@
|
|||
Message-based devices
|
||||
=====================
|
||||
|
||||
Fusion message devices
|
||||
----------------------
|
||||
|
||||
.. kernel-doc:: drivers/message/fusion/mptbase.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/message/fusion/mptscsih.c
|
||||
:export:
|
||||
|
||||
|
|
@ -0,0 +1,50 @@
|
|||
Parallel Port Devices
|
||||
=====================
|
||||
|
||||
.. kernel-doc:: include/linux/parport.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/parport/ieee1284.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/parport/share.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/parport/daisy.c
|
||||
:internal:
|
||||
|
||||
16x50 UART Driver
|
||||
=================
|
||||
|
||||
.. kernel-doc:: drivers/tty/serial/serial_core.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: drivers/tty/serial/8250/8250_core.c
|
||||
:export:
|
||||
|
||||
Pulse-Width Modulation (PWM)
|
||||
============================
|
||||
|
||||
Pulse-width modulation is a modulation technique primarily used to
|
||||
control power supplied to electrical devices.
|
||||
|
||||
The PWM framework provides an abstraction for providers and consumers of
|
||||
PWM signals. A controller that provides one or more PWM signals is
|
||||
registered as :c:type:`struct pwm_chip <pwm_chip>`. Providers
|
||||
are expected to embed this structure in a driver-specific structure.
|
||||
This structure contains fields that describe a particular chip.
|
||||
|
||||
A chip exposes one or more PWM signal sources, each of which exposed as
|
||||
a :c:type:`struct pwm_device <pwm_device>`. Operations can be
|
||||
performed on PWM devices to control the period, duty cycle, polarity and
|
||||
active state of the signal.
|
||||
|
||||
Note that PWM devices are exclusive resources: they can always only be
|
||||
used by one consumer at a time.
|
||||
|
||||
.. kernel-doc:: include/linux/pwm.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/pwm/core.c
|
||||
:export:
|
||||
|
||||
|
|
@ -0,0 +1,54 @@
|
|||
Sound Devices
|
||||
=============
|
||||
|
||||
.. kernel-doc:: include/sound/core.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: sound/sound_core.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: include/sound/pcm.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: sound/core/pcm.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: sound/core/device.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: sound/core/info.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: sound/core/rawmidi.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: sound/core/sound.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: sound/core/memory.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: sound/core/pcm_memory.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: sound/core/init.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: sound/core/isadma.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: sound/core/control.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: sound/core/pcm_lib.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: sound/core/hwdep.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: sound/core/pcm_native.c
|
||||
:export:
|
||||
|
||||
.. kernel-doc:: sound/core/memalloc.c
|
||||
:export:
|
||||
|
||||
|
|
@ -0,0 +1,53 @@
|
|||
Serial Peripheral Interface (SPI)
|
||||
=================================
|
||||
|
||||
SPI is the "Serial Peripheral Interface", widely used with embedded
|
||||
systems because it is a simple and efficient interface: basically a
|
||||
multiplexed shift register. Its three signal wires hold a clock (SCK,
|
||||
often in the range of 1-20 MHz), a "Master Out, Slave In" (MOSI) data
|
||||
line, and a "Master In, Slave Out" (MISO) data line. SPI is a full
|
||||
duplex protocol; for each bit shifted out the MOSI line (one per clock)
|
||||
another is shifted in on the MISO line. Those bits are assembled into
|
||||
words of various sizes on the way to and from system memory. An
|
||||
additional chipselect line is usually active-low (nCS); four signals are
|
||||
normally used for each peripheral, plus sometimes an interrupt.
|
||||
|
||||
The SPI bus facilities listed here provide a generalized interface to
|
||||
declare SPI busses and devices, manage them according to the standard
|
||||
Linux driver model, and perform input/output operations. At this time,
|
||||
only "master" side interfaces are supported, where Linux talks to SPI
|
||||
peripherals and does not implement such a peripheral itself. (Interfaces
|
||||
to support implementing SPI slaves would necessarily look different.)
|
||||
|
||||
The programming interface is structured around two kinds of driver, and
|
||||
two kinds of device. A "Controller Driver" abstracts the controller
|
||||
hardware, which may be as simple as a set of GPIO pins or as complex as
|
||||
a pair of FIFOs connected to dual DMA engines on the other side of the
|
||||
SPI shift register (maximizing throughput). Such drivers bridge between
|
||||
whatever bus they sit on (often the platform bus) and SPI, and expose
|
||||
the SPI side of their device as a :c:type:`struct spi_master
|
||||
<spi_master>`. SPI devices are children of that master,
|
||||
represented as a :c:type:`struct spi_device <spi_device>` and
|
||||
manufactured from :c:type:`struct spi_board_info
|
||||
<spi_board_info>` descriptors which are usually provided by
|
||||
board-specific initialization code. A :c:type:`struct spi_driver
|
||||
<spi_driver>` is called a "Protocol Driver", and is bound to a
|
||||
spi_device using normal driver model calls.
|
||||
|
||||
The I/O model is a set of queued messages. Protocol drivers submit one
|
||||
or more :c:type:`struct spi_message <spi_message>` objects,
|
||||
which are processed and completed asynchronously. (There are synchronous
|
||||
wrappers, however.) Messages are built from one or more
|
||||
:c:type:`struct spi_transfer <spi_transfer>` objects, each of
|
||||
which wraps a full duplex SPI transfer. A variety of protocol tweaking
|
||||
options are needed, because different chips adopt very different
|
||||
policies for how they use the bits transferred with SPI.
|
||||
|
||||
.. kernel-doc:: include/linux/spi/spi.h
|
||||
:internal:
|
||||
|
||||
.. kernel-doc:: drivers/spi/spi.c
|
||||
:functions: spi_register_board_info
|
||||
|
||||
.. kernel-doc:: drivers/spi/spi.c
|
||||
:export:
|
||||
|
|
@ -1,75 +0,0 @@
|
|||
HSI - High-speed Synchronous Serial Interface
|
||||
|
||||
1. Introduction
|
||||
~~~~~~~~~~~~~~~
|
||||
|
||||
High Speed Syncronous Interface (HSI) is a fullduplex, low latency protocol,
|
||||
that is optimized for die-level interconnect between an Application Processor
|
||||
and a Baseband chipset. It has been specified by the MIPI alliance in 2003 and
|
||||
implemented by multiple vendors since then.
|
||||
|
||||
The HSI interface supports full duplex communication over multiple channels
|
||||
(typically 8) and is capable of reaching speeds up to 200 Mbit/s.
|
||||
|
||||
The serial protocol uses two signals, DATA and FLAG as combined data and clock
|
||||
signals and an additional READY signal for flow control. An additional WAKE
|
||||
signal can be used to wakeup the chips from standby modes. The signals are
|
||||
commonly prefixed by AC for signals going from the application die to the
|
||||
cellular die and CA for signals going the other way around.
|
||||
|
||||
+------------+ +---------------+
|
||||
| Cellular | | Application |
|
||||
| Die | | Die |
|
||||
| | - - - - - - CAWAKE - - - - - - >| |
|
||||
| T|------------ CADATA ------------>|R |
|
||||
| X|------------ CAFLAG ------------>|X |
|
||||
| |<----------- ACREADY ------------| |
|
||||
| | | |
|
||||
| | | |
|
||||
| |< - - - - - ACWAKE - - - - - - -| |
|
||||
| R|<----------- ACDATA -------------|T |
|
||||
| X|<----------- ACFLAG -------------|X |
|
||||
| |------------ CAREADY ----------->| |
|
||||
| | | |
|
||||
| | | |
|
||||
+------------+ +---------------+
|
||||
|
||||
2. HSI Subsystem in Linux
|
||||
~~~~~~~~~~~~~~~~~~~~~~~~~
|
||||
|
||||
In the Linux kernel the hsi subsystem is supposed to be used for HSI devices.
|
||||
The hsi subsystem contains drivers for hsi controllers including support for
|
||||
multi-port controllers and provides a generic API for using the HSI ports.
|
||||
|
||||
It also contains HSI client drivers, which make use of the generic API to
|
||||
implement a protocol used on the HSI interface. These client drivers can
|
||||
use an arbitrary number of channels.
|
||||
|
||||
3. hsi-char Device
|
||||
~~~~~~~~~~~~~~~~~~
|
||||
|
||||
Each port automatically registers a generic client driver called hsi_char,
|
||||
which provides a charecter device for userspace representing the HSI port.
|
||||
It can be used to communicate via HSI from userspace. Userspace may
|
||||
configure the hsi_char device using the following ioctl commands:
|
||||
|
||||
* HSC_RESET:
|
||||
- flush the HSI port
|
||||
|
||||
* HSC_SET_PM
|
||||
- enable or disable the client.
|
||||
|
||||
* HSC_SEND_BREAK
|
||||
- send break
|
||||
|
||||
* HSC_SET_RX
|
||||
- set RX configuration
|
||||
|
||||
* HSC_GET_RX
|
||||
- get RX configuration
|
||||
|
||||
* HSC_SET_TX
|
||||
- set TX configuration
|
||||
|
||||
* HSC_GET_TX
|
||||
- get TX configuration
|
||||
|
|
@ -13,6 +13,7 @@ Contents:
|
|||
|
||||
kernel-documentation
|
||||
dev-tools/tools
|
||||
driver-api/index
|
||||
media/index
|
||||
gpu/index
|
||||
|
||||
|
|
|
|||
|
|
@ -5606,7 +5606,7 @@ M: Sebastian Reichel <sre@kernel.org>
|
|||
T: git git://git.kernel.org/pub/scm/linux/kernel/git/sre/linux-hsi.git
|
||||
S: Maintained
|
||||
F: Documentation/ABI/testing/sysfs-bus-hsi
|
||||
F: Documentation/hsi.txt
|
||||
F: Documentation/device-drivers/serial-interfaces.rst
|
||||
F: drivers/hsi/
|
||||
F: include/linux/hsi/
|
||||
F: include/uapi/linux/hsi/
|
||||
|
|
|
|||
Loading…
Reference in New Issue