Commit Graph

29 Commits

Author SHA1 Message Date
Corentin Labbe 3d50b95b50 i2c: smbus: add DDR support for SPD
On my x05 laptop I got:
Memory type 0x12 not supported yet, not instantiating SPD

Adding the 0x12 case lead to a successful instantiated SPD AT24 EEPROM.
i801_smbus 0000:00:1f.3: SMBus using polling
i2c i2c-6: 2/2 memory slots populated (from DMI)
at24 6-0050: 256 byte spd EEPROM, read-only
i2c i2c-6: Successfully instantiated SPD at 0x50
at24 6-0051: 256 byte spd EEPROM, read-only

And then, I decoded it successfully via decode-dimms.

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
2022-12-01 23:39:02 +01:00
Uwe Kleine-König ed5c2f5fd1 i2c: Make remove callback return void
The value returned by an i2c driver's remove function is mostly ignored.
(Only an error message is printed if the value is non-zero that the
error is ignored.)

So change the prototype of the remove function to return no value. This
way driver authors are not tempted to assume that passing an error to
the upper layer is a good idea. All drivers are adapted accordingly.
There is no intended change of behaviour, all callbacks were prepared to
return 0 before.

Reviewed-by: Peter Senna Tschudin <peter.senna@gmail.com>
Reviewed-by: Jeremy Kerr <jk@codeconstruct.com.au>
Reviewed-by: Benjamin Mugnier <benjamin.mugnier@foss.st.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Crt Mori <cmo@melexis.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Marek Behún <kabel@kernel.org> # for leds-turris-omnia
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Petr Machata <petrm@nvidia.com> # for mlxsw
Reviewed-by: Maximilian Luz <luzmaximilian@gmail.com> # for surface3_power
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> # for bmc150-accel-i2c + kxcjk-1013
Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> # for media/* + staging/media/*
Acked-by: Miguel Ojeda <ojeda@kernel.org> # for auxdisplay/ht16k33 + auxdisplay/lcd2s
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com> # for versaclock5
Reviewed-by: Ajay Gupta <ajayg@nvidia.com> # for ucsi_ccg
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> # for iio
Acked-by: Peter Rosin <peda@axentia.se> # for i2c-mux-*, max9860
Acked-by: Adrien Grassein <adrien.grassein@gmail.com> # for lontium-lt8912b
Reviewed-by: Jean Delvare <jdelvare@suse.de> # for hwmon, i2c-core and i2c/muxes
Acked-by: Corey Minyard <cminyard@mvista.com> # for IPMI
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Sebastian Reichel <sebastian.reichel@collabora.com> # for drivers/power
Acked-by: Krzysztof Hałasa <khalasa@piap.pl>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
2022-08-16 12:46:26 +02:00
Wolfram Sang 0b0221d9cd i2c: move core from strlcpy to strscpy
Follow the advice of the below link and prefer 'strscpy'. Conversion is
easy because no code used the return value. It has been done with a
simple sed invocation.

Link: https://lore.kernel.org/r/CAHk-=wgfRnXz0W3D37d01q3JFkr_i_uTL=V6A6G1oUZcprmknw@mail.gmail.com/
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
2022-08-11 23:02:52 +02:00
Akhil R a263a84088 i2c: smbus: Use device_*() functions instead of of_*()
Change of_*() functions to device_*() for firmware agnostic usage.
This allows to have the smbus_alert interrupt without any changes
in the controller drivers using the ACPI table.

Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
2022-01-28 21:56:34 +01:00
Alain Volmat 2a71593da3 i2c: smbus: add core function handling SMBus host-notify
SMBus Host-Notify protocol, from the adapter point of view
consist of receiving a message from a client, including the
client address and some other data.

It can be simply handled by creating a new slave device
and registering a callback performing the parsing of the
message received from the client.

This commit introduces two new core functions
  * i2c_new_slave_host_notify_device
  * i2c_free_slave_host_notify_device
that take care of registration of the new slave device and
callback and will call i2c_handle_smbus_host_notify once a
Host-Notify event is received.

Signed-off-by: Alain Volmat <alain.volmat@st.com>
Reviewed-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
2020-09-09 10:38:28 +02:00
Jean Delvare 5ace60859e i2c: smbus: Add a way to instantiate SPD EEPROMs automatically
In simple cases we can instantiate SPD EEPROMs on the SMBus
automatically. Start with just DDR2, DDR3 and DDR4 on x86 for now,
and only for systems with no more than 4 memory slots. These
limitations may be lifted later.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
[wsa: minor change for new API]
Signed-off-by: Wolfram Sang <wsa@kernel.org>
2020-05-29 12:53:04 +02:00
Wolfram Sang ed68052226 i2c: convert SMBus alert setup function to return an ERRPTR
Only few drivers use this call, so drivers and I2C core are converted at
once with this patch. By simply using i2c_new_client_device() instead of
i2c_new_device(), we easily can return an ERRPTR for this function as
well. To make out of tree users aware that something changed, the
function is renamed to i2c_new_smbus_alert_device().

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2020-03-10 12:19:52 +01:00
Corey Minyard dca0dd28fa i2c: smbus: Don't filter out duplicate alerts
Getting the same alert twice in a row is legal and normal,
especially on a fast device (like running in qemu).  Kind of
like interrupts.  So don't report duplicate alerts, and deliver
them normally.

[JD: Fixed subject]

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Jean Delvare <jdelvare@suse.de>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2019-11-25 17:13:34 +01:00
Thomas Gleixner c942fddf87 treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 157
Based on 3 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 as published by
  the free software foundation either version 2 of the license or at
  your option any later version 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

  this program 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 [author] [kishon] [vijay] [abraham]
  [i] [kishon]@[ti] [com] 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

  this program 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 [author] [graeme] [gregory]
  [gg]@[slimlogic] [co] [uk] [author] [kishon] [vijay] [abraham] [i]
  [kishon]@[ti] [com] [based] [on] [twl6030]_[usb] [c] [author] [hema]
  [hk] [hemahk]@[ti] [com] 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

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 1105 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: Kate Stewart <kstewart@linuxfoundation.org>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070033.202006027@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-30 11:26:37 -07:00
Phil Reid 69d17246ab i2c: i2c-smbus: add of_i2c_setup_smbus_alert
This commit adds of_i2c_setup_smbus_alert which allows the smbalert
driver to be attached to an i2c adapter via the device tree.

Signed-off-by: Phil Reid <preid@electromag.com.au>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2017-10-28 23:42:47 +02:00
Phil Reid 3c0a60bee1 i2c: i2c-smbus: Move i2c_setup_smbus_alert from i2c-smbus to i2c-core-smbus
In preparation to adding of_i2c_setup_smbus_alert() move
i2c_setup_smbus_alert() to core module. of_i2c_setup_smbus_alert()
will call i2c_setup_smbus_alert() and this avoid module dependecy issues.

Signed-off-by: Phil Reid <preid@electromag.com.au>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2017-10-28 23:42:36 +02:00
Phil Reid 9b9f2b8bc2 i2c: i2c-smbus: Use threaded irq for smbalert
Prior to this commit the smbalert_irq was handling in the hard irq
context. This change switch to using a thread irq which avoids the need
for the work thread. Using threaded irq also removes the need for the
edge_triggered flag as the enabling / disabling of the hard irq for level
triggered interrupts will be handled by the irq core.

Without this change have an irq connected to something like an i2c gpio
resulted in a null ptr deferences. Specifically handle_nested_irq calls
the threaded irq handler.

There are currently 3 in tree drivers affected by this change.

i2c-parport driver calls i2c_handle_smbus_alert in a hard irq context.
This driver use edge trigger interrupts which skip the enable / disable
calls. But it still need to handle the smbus transaction on a thread. So
the work thread is kept for this driver.

i2c-parport-light & i2c-thunderx-pcidrv provide the irq number in the
setup which will result in the thread irq being used.

i2c-parport-light is edge trigger so the enable / disable call was
skipped as well.

i2c-thunderx-pcidrv is getting the edge / level trigger setting from of
data and was setting the flag as required. However the irq core should
handle this automatically.

Signed-off-by: Phil Reid <preid@electromag.com.au>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2017-10-28 23:42:26 +02:00
Benjamin Tissoires 4d5538f588 i2c: use an IRQ to report Host Notify events, not alert
The current SMBus Host Notify implementation relies on .alert() to
relay its notifications. However, the use cases where SMBus Host
Notify is needed currently is to signal data ready on touchpads.

This is closer to an IRQ than a custom API through .alert().
Given that the 2 touchpad manufacturers (Synaptics and Elan) that
use SMBus Host Notify don't put any data in the SMBus payload, the
concept actually matches one to one.

Benefits are multiple:
- simpler code and API: the client will just have an IRQ, and
  nothing needs to be added in the adapter beside internally
  enabling it.
- no more specific workqueue, the threading is handled by IRQ core
  directly (when required)
- no more races when removing the device (the drivers are already
  required to disable irq on remove)
- simpler handling for drivers: use plain regular IRQs
- no more dependency on i2c-smbus for i2c-i801 (and any other adapter)
- the IRQ domain is created automatically when the adapter exports
  the Host Notify capability
- the IRQ are assign only if ACPI, OF and the caller did not assign
  one already
- the domain is automatically destroyed on remove
- fewer lines of code (minus 20, yeah!)

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2016-11-24 16:22:06 +01:00
Jean Delvare 1847bbd709 i2c: i2c-smbus: fix i2c_handle_smbus_host_notify documentation
The parameter description is from a previous implementation, update
it to describe the actual implementation.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2016-07-18 20:09:54 +02:00
Benjamin Tissoires e456cd37bc i2c: smbus: add SMBus Host Notify support
SMBus Host Notify allows a slave device to act as a master on a bus to
notify the host of an interrupt. On Intel chipsets, the functionality
is directly implemented in the firmware. We just need to export a
function to call .alert() on the proper device driver.

i2c_handle_smbus_host_notify() behaves like i2c_handle_smbus_alert().
When called, it schedules a task that will be able to sleep to go through
the list of devices attached to the adapter.

The current implementation allows one Host Notification to be scheduled
while an other is running.

Tested-by: Andrew Duggan <aduggan@synaptics.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2016-06-17 13:24:05 +02:00
Benjamin Tissoires b4f210541f i2c: add a protocol parameter to the alert callback
.alert() is meant to be generic, but there is currently no way
for the device driver to know which protocol generated the alert.
Add a parameter in .alert() to help the device driver to understand
what is given in data.

This patch is required to have the support of SMBus Host Notify protocol
through .alert().

Tested-by: Andrew Duggan <aduggan@synaptics.com>
For hwmon:
Acked-by: Guenter Roeck <linux@roeck-us.net>
For IPMI:
Acked-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2016-06-17 12:41:25 +02:00
Wolfram Sang 62c874ab4d i2c: i2c-smbus: sort includes
I request this for drivers, so the core should adhere to sorted includes as
well.

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2016-02-20 23:33:39 +01:00
Shailendra Verma edc9102a8e i2c: smbus: fix typo in commet
Signed-off-by: Shailendra Verma <shailendra.capricorn@gmail.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2015-06-01 08:41:26 +09:00
Wolfram Sang ca1f8da9ac i2c: remove FSF address
We have a central copy of the GPL for that. Some addresses were already
outdated.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
2014-11-07 18:35:33 +01:00
Jean Delvare 7c81c60f37 Update Jean Delvare's e-mail address
Signed-off-by: Jean Delvare <khali@linux-fr.org>
2014-01-29 20:40:08 +01:00
Lars-Peter Clausen 0acc2b3213 i2c: Remove redundant 'driver' field from the i2c_client struct
The 'driver' field of the i2c_client struct is redundant. The same data can be
accessed through to_i2c_driver(client->dev.driver). The generated code for both
approaches in more or less the same.

E.g. on ARM the expression client->driver->command(...) generates

		...
		ldr     r3, [r0, #28]
		ldr     r3, [r3, #32]
		blx     r3
		...

and the expression to_i2c_driver(client->dev.driver)->command(...) generates

		...
		ldr     r3, [r0, #160]
    	ldr     r3, [r3, #-4]
    	blx     r3
		...

Other architectures will generate similar code.

All users of the 'driver' field outside of the I2C core have already been
converted. So this only leaves the core itself. This patch converts the
remaining few users in the I2C core and then removes the 'driver' field from the
i2c_client struct.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2013-10-03 22:28:31 +02:00
Jingoo Han 6d4028c644 i2c: use dev_get_platdata()
Use the wrapper function for retrieving the platform data instead of
accessing dev->platform_data directly.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2013-08-19 19:46:30 +02:00
Julia Lawall 71b578452e i2c-smbus: Convert kzalloc to devm_kzalloc
Converting kzalloc to devm_kzalloc simplifies the code and ensures that the
result, alert, is freed after the irq allocated by the subsequent
devm_request_irq.  This in turn ensures that when an interrupt can be
triggered, the alert structure is still available.

The problem of a free after a devm_request_irq was found using the
following semantic match (http://coccinelle.lip6.fr/)

// <smpl>
@r exists@
expression e1,e2,x,a,b,c,d;
identifier free;
position p1,p2;
@@

  devm_request_irq@p1(e1,e2,...,x)
  ... when any
      when != e2 = a
      when != x = b
  if (...) {
    ... when != e2 = c
        when != x = d
    free@p2(...,x,...);
    ...
    return ...;
  }
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
2012-10-05 22:23:52 +02:00
Fabio Estevam fda2f4af37 i2c-smbus: Use module_i2c_driver()
Using module_i2c_driver() makes the code smaller and cleaner.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
2012-07-24 14:13:57 +02:00
Jean Delvare 5694f8a888 i2c: Update the FSF address
Signed-off-by: Jean Delvare <khali@linux-fr.org>
2012-03-26 21:47:19 +02:00
Wolfram Sang fbae3fb154 i2c: Remove all i2c_set_clientdata(client, NULL) in drivers
I2C drivers can use the clientdata-pointer to point to private data. As I2C
devices are not really unregistered, but merely detached from their driver, it
used to be the drivers obligation to clear this pointer during remove() or a
failed probe(). As a couple of drivers forgot to do this, it was agreed that it
was cleaner if the i2c-core does this clearance when appropriate, as there is
no guarantee for the lifetime of the clientdata-pointer after remove() anyhow.
This feature was added to the core with commit
e4a7b9b04d to fix the faulty drivers.

As there is no need anymore to clear the clientdata-pointer, remove all current
occurrences in the drivers to simplify the code and prevent confusion.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Richard Purdie <rpurdie@linux.intel.com>
Acked-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
2010-06-03 11:33:58 +02:00
Tejun Heo 5a0e3ad6af include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files.  percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.

percpu.h -> slab.h dependency is about to be removed.  Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability.  As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.

  http://userweb.kernel.org/~tj/misc/slabh-sweep.py

The script does the followings.

* Scan files for gfp and slab usages and update includes such that
  only the necessary includes are there.  ie. if only gfp is used,
  gfp.h, if slab is used, slab.h.

* When the script inserts a new include, it looks at the include
  blocks and try to put the new include such that its order conforms
  to its surrounding.  It's put in the include block which contains
  core kernel includes, in the same order that the rest are ordered -
  alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
  doesn't seem to be any matching order.

* If the script can't find a place to put a new include (mostly
  because the file doesn't have fitting include block), it prints out
  an error message indicating which .h file needs to be added to the
  file.

The conversion was done in the following steps.

1. The initial automatic conversion of all .c files updated slightly
   over 4000 files, deleting around 700 includes and adding ~480 gfp.h
   and ~3000 slab.h inclusions.  The script emitted errors for ~400
   files.

2. Each error was manually checked.  Some didn't need the inclusion,
   some needed manual addition while adding it to implementation .h or
   embedding .c file was more appropriate for others.  This step added
   inclusions to around 150 files.

3. The script was run again and the output was compared to the edits
   from #2 to make sure no file was left behind.

4. Several build tests were done and a couple of problems were fixed.
   e.g. lib/decompress_*.c used malloc/free() wrappers around slab
   APIs requiring slab.h to be added manually.

5. The script was run on all .h files but without automatically
   editing them as sprinkling gfp.h and slab.h inclusions around .h
   files could easily lead to inclusion dependency hell.  Most gfp.h
   inclusion directives were ignored as stuff from gfp.h was usually
   wildly available and often used in preprocessor macros.  Each
   slab.h inclusion directive was examined and added manually as
   necessary.

6. percpu.h was updated not to include slab.h.

7. Build test were done on the following configurations and failures
   were fixed.  CONFIG_GCOV_KERNEL was turned off for all tests (as my
   distributed build env didn't work with gcov compiles) and a few
   more options had to be turned off depending on archs to make things
   build (like ipr on powerpc/64 which failed due to missing writeq).

   * x86 and x86_64 UP and SMP allmodconfig and a custom test config.
   * powerpc and powerpc64 SMP allmodconfig
   * sparc and sparc64 SMP allmodconfig
   * ia64 SMP allmodconfig
   * s390 SMP allmodconfig
   * alpha SMP allmodconfig
   * um on x86_64 SMP allmodconfig

8. percpu.h modifications were reverted so that it could be applied as
   a separate patch and serve as bisection point.

Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-30 22:02:32 +09:00
Stephen Rothwell f635a1e74b i2c-smbus: Use device_lock/device_unlock
Use the new device locking/unlocking API.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
2010-03-13 20:56:51 +01:00
Jean Delvare b5527a7766 i2c: Add SMBus alert support
SMBus alert support. The SMBus alert protocol allows several SMBus
slave devices to share a single interrupt pin on the SMBus master,
while still allowing the master to know which slave triggered the
interrupt.

This is based on preliminary work by David Brownell. The key
difference between David's implementation and mine is that his was
part of i2c-core, while mine is split into a separate, standalone
module named i2c-smbus. The i2c-smbus module is meant to include
support for all SMBus extensions to the I2C protocol in the future.

The benefit of this approach is a zero cost for I2C bus segments which
do not need SMBus alert support. Where David's implementation
increased the size of struct i2c_adapter by 7% (40 bytes on i386),
mine doesn't touch it. Where David's implementation added over 150
lines of code to i2c-core (+10%), mine doesn't touch it. The only
change that touches all the users of the i2c subsystem is a new
callback in struct i2c_driver (common to both implementations.) I seem
to remember Trent was worried about the footprint of David'd
implementation, hopefully mine addresses the issue.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Trent Piepho <tpiepho@freescale.com>
2010-03-02 12:23:42 +01:00