On Fri, Jun 19, 2020 at 05:27:33PM +0100, Jonathan Cameron wrote:
On Wed, 17 Jun 2020 21:29:27 -0400
Sasha Levin <sashal@xxxxxxxxxx> wrote:
From: Lars-Peter Clausen <lars@xxxxxxxxxx>
[ Upstream commit b7329249ea5b08b2a1c2c3f24a2f4c495c4f14b8 ]
Before activating a buffer make sure that at least one channel is enabled.
Activating a buffer with 0 channels enabled doesn't make too much sense and
disallowing this case makes sure that individual driver don't have to add
special case code to handle it.
Currently, without this patch enabling a buffer is possible and no error is
produced. With this patch -EINVAL is returned.
An example of execution with this patch and some instrumented print-code:
root@analog:~# cd /sys/bus/iio/devices/iio\:device3/buffer
root@analog:/sys/bus/iio/devices/iio:device3/buffer# echo 1 > enable
0: iio_verify_update 748 indio_dev->masklength 2 *insert_buffer->scan_mask 00000000
1: iio_verify_update 753
2:__iio_update_buffers 1115 ret -22
3: iio_buffer_store_enable 1241 ret -22
-bash: echo: write error: Invalid argument
1, 2 & 3 are exit-error paths. 0 the first print in iio_verify_update()
rergardless of error path.
Without this patch (and same instrumented print-code):
root@analog:~# cd /sys/bus/iio/devices/iio\:device3/buffer
root@analog:/sys/bus/iio/devices/iio:device3/buffer# echo 1 > enable
0: iio_verify_update 748 indio_dev->masklength 2 *insert_buffer->scan_mask 00000000
root@analog:/sys/bus/iio/devices/iio:device3/buffer#
Buffer is enabled with no error.
Note from Jonathan: Probably not suitable for automatic application to stable.
This has been there from the very start. It tidies up an odd corner
case but won't effect any 'real' users.
As noted. I don't think it matters if we do apply this to stable.
It closes an interface oddity rather than an actual known bug.
I'll drop it, thanks!
--
Thanks,
Sasha
