For some embedded systems, a workflow involving external kernel modules
that implement IIO devices is more practical than working with in-tree
sources.
Kconfig symbols without any titles do not show up in menuconfig, and as
such are more difficult to configure granularly, as they need to be
selected by potentially unused/un-needed drivers.
This change adds a title to the IIO_TRIGGERED_BUFFER Kconfig symbol.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20200924111758.196367-4-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
For some embedded systems, a workflow involving external kernel modules
that implement IIO devices is more practical than working with in-tree
sources.
Kconfig symbols without any titles do not show up in menuconfig, and as
such are more difficult to configure granularly, as they need to be
selected by potentially unused/un-needed drivers.
This change adds titles to the IIO DMA Kconfig symbols to address this.
This change also updates DMAengine -> DMAEngine, which is the
correct/nitpick-y name of the framework.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20200924111758.196367-2-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This is to encourage the use of devm_iio_dmaengine_buffer_alloc().
Currently the managed version of the DMAEngine buffer alloc is the only
function used from this part of the framework.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20200923121810.944075-1-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
A transfer may fall shorter than the bytes in the block.
This information is available in the residue from the DMA engine, so we can
compute actual `bytes_used` with that by subtracting the residue.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20200826052011.13348-1-lars@metafoo.de
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
All devices using a triggered buffer need to attach and detach the trigger
to the device in order to properly work. Instead of doing this in each and
every driver by hand move this into the core.
At this point in time, all drivers should have been resolved to
attach/detach the poll-function in the same order.
This patch removes all explicit calls of iio_triggered_buffer_postenable()
& iio_triggered_buffer_predisable() in all drivers, since the core handles
now the pollfunc attach/detach.
The more peculiar change is for the 'at91-sama5d2_adc' driver, since it's
not immediately obvious that removing the hooks doesn't break anything.
Eugen was able to test on at91-sama5d2-adc driver, sama5d2-xplained board.
All seems to be fine.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Tested-by: Eugen Hristev <eugen.hristev@microchip.com> #for at91-sama5d2-adc
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
It's unused so far, so it can be removed. Also makes sense to remove it
to discourage weird uses of this call during review.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
It's unused so far, so it can be removed. Also makes sense to remove it
to discourage weird uses of this call during review.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
It's unused so far, so it can be removed. Also makes sense to remove it
to discourage weird uses of this call during review.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
The IIO DMA buffer is a DMA buffer implementation. As such it should
include buffer_impl.h rather than buffer.h.
The include to buffer.h in buffer-dma.h should be buffer_impl.h so it has
access to the struct iio_buffer definition. The code currently only works
because all places that use buffer-dma.h include buffer_impl.h before it.
The include to buffer.h in industrialio-buffer-dma.c can be removed since
those file does not reference any of buffer consumer functions.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Tested-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Currently, when using a 'iio_dmaengine_buffer_alloc()', an matching call to
'iio_dmaengine_buffer_free()' must be made.
With this change, this can be avoided by using
'devm_iio_dmaengine_buffer_alloc()'. The buffer will get free'd via the
device's devres handling.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
The 'size_t' type behaves differently on 64-bit architectures, and causes
compiler a warning of the sort "format '%u' expects argument of type
'unsigned int', but argument 3 has type 'size_t {aka long unsigned int}'".
This change adds the correct specifier for the 'align' field.
Fixes: 4538c18568 ("iio: buffer-dmaengine: Report buffer length requirements")
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
It is implied that 'read' will read the first n bytes and not e.g. bytes
only from offsets within the buffer that are a prime number.
This change is non-functional, mostly just a rename.
A secondary intent with this patch is to make room later to add a write
callback.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
The dmaengine buffer has some length alignment requirements that can differ
from platform to platform. If the length alignment requirements are not met
unexpected behavior like dropping of samples can occur.
Currently these requirements are not reported and applications need to know
the requirements of the platform by some out-of-band means.
Add a new buffer attribute that reports the length alignment requirements
called `length_align_bytes`. The reported length alignment is in bytes that
means the buffer length alignment in sample sets depends on the number of
enabled channels and the bytes per channel. Applications using this
attribute to determine the buffer size requirements need to consider this.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Make sure that the industrialio-buffer-dmaengine has proper license
information so it can be build as a module and loaded without tainting the
kernel.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Based on 2 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation #
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 4122 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Based on 1 normalized pattern(s):
licensed under the gpl 2
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 135 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Reviewed-by: Steve Winslow <swinslow@gmail.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190528170026.071193225@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Based on 1 normalized pattern(s):
licensed under the gpl 2 or later
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 82 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190524100845.150836982@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add SPDX license identifiers to all Make/Kconfig files which:
- Have no license information of any form
These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:
GPL-2.0-only
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add SPDX license identifiers to all files which:
- Have no license information of any form
- Have MODULE_LICENCE("GPL*") inside which was used in the initial
scan/conversion to ignore the file
These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:
GPL-2.0-only
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Switch to bitmap_zalloc() to show clearly what we are allocating.
Besides that it returns pointer of bitmap type instead of opaque void *.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Currently, the following causes a kernel OOPS in memcpy:
echo 1073741825 > buffer/length
echo 1 > buffer/enable
Note that using 1073741824 instead of 1073741825 causes "write error:
Cannot allocate memory" but no OOPS.
This is because 1073741824 == 2^30 and 1073741825 == 2^30+1. Since kfifo
rounds up to the nearest power of 2, it will actually call kmalloc with
roundup_pow_of_two(length) * bytes_per_datum.
Using length == 1073741825 and bytes_per_datum == 2, we get:
kmalloc(roundup_pow_of_two(1073741825) * 2
or kmalloc(2147483648 * 2)
or kmalloc(4294967296)
or kmalloc(UINT_MAX + 1)
so this overflows to 0, causing kmalloc to return ZERO_SIZE_PTR and
subsequent memcpy to fail once the device is enabled.
Fix this by checking for overflow prior to allocating a kfifo. With this
check added, the above code returns -EINVAL when enabling the buffer,
rather than causing an OOPS.
Signed-off-by: Martin Kelly <mkelly@xevo.com>
cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Currently, we use int for buffer length and bytes_per_datum. However,
kfifo uses unsigned int for length and size_t for element size. We need
to make sure these matches or we will have bugs related to overflow (in
the range between INT_MAX and UINT_MAX for length, for example).
In addition, set_bytes_per_datum uses size_t while bytes_per_datum is an
int, which would cause bugs for large values of bytes_per_datum.
Change buffer length to use unsigned int and bytes_per_datum to use
size_t.
Signed-off-by: Martin Kelly <mkelly@xevo.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This is the mindless scripted replacement of kernel use of POLL*
variables as described by Al, done by this script:
for V in IN OUT PRI ERR RDNORM RDBAND WRNORM WRBAND HUP RDHUP NVAL MSG; do
L=`git grep -l -w POLL$V | grep -v '^t' | grep -v /um/ | grep -v '^sa' | grep -v '/poll.h$'|grep -v '^D'`
for f in $L; do sed -i "-es/^\([^\"]*\)\(\<POLL$V\>\)/\\1E\\2/" $f; done
done
with de-mangling cleanups yet to come.
NOTE! On almost all architectures, the EPOLL* constants have the same
values as the POLL* constants do. But they keyword here is "almost".
For various bad reasons they aren't the same, and epoll() doesn't
actually work quite correctly in some cases due to this on Sparc et al.
The next patch from Al will sort out the final differences, and we
should be all done.
Scripted-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add iio consumer API to set buffer size and watermark according
to sysfs API.
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Add devm_iio_hw_consumer_alloc function that calls iio_hw_consumer_free
when the device is unbound from the bus.
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Hardware consumer interface can be used when one IIO device has
a direct connection to another device in hardware.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.
By default all files without license information are under the default
license of the kernel, which is GPL version 2.
Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.
This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.
How this work was done:
Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,
Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.
The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.
The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.
Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).
All documentation files were explicitly excluded.
The following heuristics were used to determine which SPDX license
identifiers to apply.
- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.
For non */uapi/* files that summary was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139
and resulted in the first patch in this series.
If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:
SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930
and resulted in the second patch in this series.
- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:
SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1
and that resulted in the third patch in this series.
- when the two scanners agreed on the detected license(s), that became
the concluded license(s).
- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.
- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).
- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.
- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.
In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.
Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.
Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.
In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.
Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct
This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.
These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Add buffer_impl.h as buffer.h was split into interface for using and
for internals. Without this industrialio-buffer-dmaengine.c fails
to compile.
Fixes:
commit 33dd94cb97 ("iio:buffer.h - split
into buffer.h and buffer_impl.h")
Signed-off-by: Phil Reid <preid@electromag.com.au>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Add buffer_impl.h as buffer.h was split into interface for using and
for internals. Without this industrialio-buffer-dma.c fails
to compile.
Fixes:
commit 33dd94cb97 ("iio:buffer.h - split
into buffer.h and buffer_impl.h")
Signed-off-by: Phil Reid <preid@electromag.com.au>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
buffer.h supplies everything needed for devices using buffers.
buffer_impl.h supplies access to the internals as needed to write
a buffer implementation.
This was really motivated by the mess that turned up in the
kernel-doc documentation pulled in by the new sphinx docs.
It made it clear that our logical separations in headers were
generally terrible. The buffer case was easy to sort out without
greatly effecting drivers so here it is.
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
These were only getting access to the internals of struct iio_dev via
the include of iio.h within buffer.h. This should always have been
explicitly included by the buffer implementations themselves.
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
As a precursor to splitting buffer.h, lets make sure all drivers
include the relevant headers rather than relying on picking them
up from kfifo_buf.h.
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Add resource managed devm_iio_triggered_buffer_setup() and
devm_iio_triggered_buffer_cleanup() to automatically clean up triggered
buffers setup by IIO drivers, thus leading to simplified IIO drivers code.
Signed-off-by: Gregor Boirie <gregor.boirie@parrot.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Add iio_channel_cb_get_iio_dev function to allow getting the
underlying iio_dev. This is useful for setting the trigger of the
consumer ADC device.
Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Use the ARRAY_SIZE macro in the for loops that access queue->fileio.blocks.
Macro is already used in a couple of places where this access occurs,
but range was hardcoded in these locations.
Signed-off-by: Phil Reid <preid@electromag.com.au>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
The DMAengine framework gained support for synchronized transfer
termination. Use the new dmaengine_terminate_sync() function instead of
dmaengine_terminate_all(), this avoids a potential race condition when
disabling the buffer.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Add a generic fully device independent DMA buffer implementation that uses
the DMAegnine framework to perform the DMA transfers. This can be used by
converter drivers that whish to provide a DMA buffer for converters that
are connected to a DMA core that implements the DMAengine API.
Apart from allocating the buffer using iio_dmaengine_buffer_alloc() and
freeing it using iio_dmaengine_buffer_free() no additional converter driver
specific code is required when using this DMA buffer implementation.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
The traditional approach used in IIO to implement buffered capture requires
the generation of at least one interrupt per sample. In the interrupt
handler the driver reads the sample from the device and copies it to a
software buffer. This approach has a rather large per sample overhead
associated with it. And while it works fine for samplerates in the range of
up to 1000 samples per second it starts to consume a rather large share of
the available CPU processing time once we go beyond that, this is
especially true on an embedded system with limited processing power. The
regular interrupt also causes increased power consumption by not allowing
the hardware into deeper sleep states, which is something that becomes more
and more important on mobile battery powered devices.
And while the recently added watermark support mitigates some of the issues
by allowing the device to generate interrupts at a rate lower than the data
output rate, this still requires a storage buffer inside the device and
even if it exists it is only a few 100 samples deep at most.
DMA support on the other hand allows to capture multiple millions or even
more samples without any CPU interaction. This allows the CPU to either go
to sleep for longer periods or focus on other tasks which increases overall
system performance and power consumption. In addition to that some devices
might not even offer a way to read the data other than using DMA, which
makes DMA mandatory to use for them.
The tasks involved in implementing a DMA buffer can be divided into two
categories. The first category is memory buffer management (allocation,
mapping, etc.) and hooking this up the IIO buffer callbacks like read(),
enable(), disable(), etc. The second category of tasks is to setup the
DMA hardware and manage the DMA transfers. Tasks from the first category
will be very similar for all IIO drivers supporting DMA buffers, while the
tasks from the second category will be hardware specific.
This patch implements a generic infrastructure that take care of the former
tasks. It provides a set of functions that implement the standard IIO
buffer iio_buffer_access_funcs callbacks. These can either be used as is or
be overloaded and augmented with driver specific code where necessary.
For the DMA buffer support infrastructure that is introduced in this series
sample data is grouped by so called blocks. A block is the basic unit at
which data is exchanged between the application and the hardware. The
application is responsible for allocating the memory associated with the
block and then passes the block to the hardware. When the hardware has
captured the amount of samples equal to size of a block it will notify the
application, which can then read the data from the block and process it.
The block size can freely chosen (within the constraints of the hardware).
This allows to make a trade-off between latency and management overhead.
The larger the block size the lower the per sample overhead but the latency
between when the data was captured and when the application will be able to
access it increases, in a similar way smaller block sizes have a larger per
sample management overhead but a lower latency. The ideal block size thus
depends on system and application requirements.
For the time being the infrastructure only implements a simple double
buffered scheme which allocates two blocks each with half the size of the
configured buffer size. This provides basic support for capturing
continuous uninterrupted data over the existing file-IO ABI. Future
extensions to the DMA buffer infrastructure will give applications a more
fine grained control over how many blocks are allocated and the size of
each block. But this requires userspace ABI additions which are
intentionally not part of this patch and will be added separately.
Tasks of the second category need to be implemented by a device specific
driver. They can be hooked up into the generic infrastructure using two
simple callbacks, submit() and abort().
The submit() callback is used to schedule DMA transfers for blocks. Once a
DMA transfer has been completed it is expected that the buffer driver calls
iio_dma_buffer_block_done() to notify. The abort() callback is used for
stopping all pending and active DMA transfers when the buffer is disabled.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
For generic IIO trigger implementations we already have a sub-directory,
but the generic buffer implementations currently reside in the IIO
top-level directory. The main reason is that things have historically grown
into this form.
With more generic buffer implementations on its way now is the perfect time
to clean this up and introduce a sub-directory for generic buffer
implementations to avoid too much clutter in the top-level directory.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Alexandru Ardelean