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

[Stephan Gerhold <stephan@gerhold.net>]

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?

Thanks,
Stephan