Re: FAILED: patch "[PATCH] iio: imu: st_lsm6dsx: Fix selection of ST_LSM6DS3_ID" failed to apply to 4.19-stable tree

[Sasha Levin <sashal@kernel.org>]

On Sun, Jan 19, 2020 at 05:15:33PM +0100, Stephan Gerhold wrote:
>On Sun, Jan 19, 2020 at 10:32:53AM -0500, Sasha Levin wrote:
>> On Sun, Jan 19, 2020 at 02:33:30PM +0100, gregkh@linuxfoundation.org wrote:
>> >
>> > The patch below does not apply to the 4.19-stable tree.
>> > If someone wants it applied there, or to any other stable or longterm
>> > tree, then please email the backport, including the original git commit
>> > id to <stable@vger.kernel.org>.
>> >
>> > thanks,
>> >
>> > greg k-h
>> >
>> > ------------------ original commit in Linus's tree ------------------
>> >
>> > From fb4fbc8904e786537e29329d791147389e1465a2 Mon Sep 17 00:00:00 2001
>> > From: Stephan Gerhold <stephan@gerhold.net>
>> > Date: Mon, 16 Dec 2019 13:41:20 +0100
>> > Subject: [PATCH] iio: imu: st_lsm6dsx: Fix selection of ST_LSM6DS3_ID
>> >
>> > At the moment, attempting to probe a device with ST_LSM6DS3_ID
>> > (e.g. using the st,lsm6ds3 compatible) fails with:
>> >
>> >    st_lsm6dsx_i2c 1-006b: unsupported whoami [69]
>> >
>> > ... even though 0x69 is the whoami listed for ST_LSM6DS3_ID.
>> >
>> > This happens because st_lsm6dsx_check_whoami() also attempts
>> > to match unspecified (zero-initialized) entries in the "id" array.
>> > ST_LSM6DS3_ID = 0 will therefore match any entry in
>> > st_lsm6dsx_sensor_settings (here: the first), because none of them
>> > actually have all 12 entries listed in the "id" array.
>> >
>> > Avoid this by additionally checking if "name" is set,
>> > which is only set for valid entries in the "id" array.
>> >
>> > Note: Although the problem was introduced earlier it did not surface until
>> > commit 52f4b1f19679 ("iio: imu: st_lsm6dsx: add support for accel/gyro unit of lsm9ds1")
>> > because ST_LSM6DS3_ID was the first entry in st_lsm6dsx_sensor_settings.
>> >
>> > Fixes: d068e4a0f921 ("iio: imu: st_lsm6dsx: add support to multiple devices with the same settings")
>> > Cc: <stable@vger.kernel.org> # 5.4
>> > Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
>> > Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
>> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>
>> I don't think that this is needed on anything older than 5.4 because
>> they don't have 801a6e0af0c6 ("iio: imu: st_lsm6dsx: add support to
>> LSM6DSO"), the fixes tag might be misleading here a bit.
>
>Correct. I didn't want to use 801a6e0af0c6 ("iio: imu: st_lsm6dsx: add
>support to LSM6DSO") as Fixes tag because that commit did not do
>anything wrong - the problem was introduced earlier, but there is no way
>to trigger it on older kernels.
>
>This is why I added # 5.5 to the Cc: stable tag.
>Are these comments still used in any way?
>Or is there a better way to encode this into the commit message?

Usually if there's a fixes: tag we'll look at that rather than the
version appended to the stable tag.

Consider maybe using two "Fixes:" tags to point at the commits that were
involved.

-- 
Thanks,
Sasha