linux-kernel - Re: [PATCH] Revert "Input: bma150 - avoid binding to bma180 if IIO bma180 driver present" and "Input: bma150

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Date:   Wed, 5 Apr 2017 21:16:28 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Aniroop Mathur <a.mathur@...sung.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        letux-kernel@...nphoenux.org
Subject: Re: [PATCH] Revert "Input: bma150 - avoid binding to bma180 if IIO bma180 driver present" and "Input: bma150 - extend chip detection for bma180"


> Am 01.04.2017 um 18:46 schrieb Dmitry Torokhov <dmitry.torokhov@...il.com>:
> 
> On Sat, Apr 01, 2017 at 04:59:26PM +0200, Hans de Goede wrote:
>> Hi,
>> 
>> On 01-04-17 16:44, H. Nikolaus Schaller wrote:
>>> This reverts commit baf28d91e7b1 ("Input: bma150 - avoid binding to bma180 if IIO bma180 driver present")
>>> and commit ef3714fdbc8d ("Input: bma150 - extend chip detection for bma180")
>>> 
>>> Rationale: initially (2012) the GTA04 device using a bma180 chip simply refereced
>>> the bma150 platform driver in its board file [1] which happened to work in all
>>> scenarios that were tested.
>>> 
>>> When conversion to DT started (2014), we needed to make the driver be still
>>> recognised. Hence we introduced the compatibility to the bma180 chip in
>>> Linux 3.15-rc5 [2] without further checks if it is really 100% compatible. This
>>> worked flawlessly for years with the GTA04 device.
>>> 
>>> Recently (2016), Hans de Goede pointed out that the chips are not as similar
>>> as they appeared and the driver works with the bma180 for the GTA04 only
>>> by good luck. He proposed to remove the bma180 support completely [3], but
>>> we still did need it until we have a replacement. Thus, a condifional compile
>>> was added.
>>> 
>>> We have now developed a generic iio-input-bridge which works with any 2 or
>>> 3 axis iio based accelerometer. It has been tested on GTA04 and Pyra and
>>> works as expected. Therefore we can remove the bma180 support from this
>>> driver completely. User-space API compatibility can be restored by using the
>>> iio-input-bridge.
>>> 
>>> Maybe it is time to convert the bma150 driver to iio as well and retire the
>>> accelerometer input drivers completely but this is a different story and task.
>>> 
>>> [1]: https://github.com/neilbrown/linux/blob/gta04/3.2.y/arch/arm/mach-omap2/board-omap3gta04.c#L976
>>> [2]: https://patchwork.kernel.org/patch/3961171/
>>> [3]: https://patchwork.kernel.org/patch/9325481/
>>> 
>>> Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
>> 
>> Looks good to me:
>> 
>> Reviewed-by: Hans de Goede <hdegoede@...hat.com>
> 
> Changed subject slightly (we are not reverting because patches were
> defective, we are removing support for bma180), and applied.

Just noticed: the subject in linux-next has a typo:
Should IMHO be "Input: bma150 - remove support for bma180"

https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=f069b5a0b27ad4a87e9351e54fbcab3d3f8a9fd5

thanks,
Nikolaus