On Sat, 2020-03-21 at 18:21 +0000, Jonathan Cameron wrote: > On Fri, 20 Mar 2020 11:16:12 +0000 > "Ardelean, Alexandru" <alexandru.Ardelean@xxxxxxxxxx> wrote: > > > On Fri, 2020-03-20 at 11:55 +0100, Lars-Peter Clausen wrote: > > > On 3/20/20 11:40 AM, Alexandru Ardelean wrote: > > > > From: Lars-Peter Clausen <lars@xxxxxxxxxx> > > > > > > > > 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. > > > > > > > > Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx> > > > > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx> > > > > --- > > > > > > > > * Found this relic-patch in our tree, from 6 years ago: > > > > https://github.com/analogdevicesinc/linux/commit/6d680e49d459c > > > > It got moved around a bit, and this is the current form in the ADI > > > > tree. > > > > So, this is also a bit of an RFC, but if the idea is valid, maybe > > > > it's > > > > worth considering upstream. I don't know of any arguments against it, > > > > but I could be surprised. > > > > > > Hm, a bit weird that this one never made it upstream considering how > > > simple it is. > > > > > > Did you check that the issue still occurs? I can't see anything in the > > > code that prevents it, but who knows, maybe it was fixed by something > > > else. > > > > i did not think to check behavior/issues; > > i'll try to make some time for that; > > I can't immediately think of anything that would stop this case. > > However, good if you could confirm it. (I don't have a setup running > right now to test against) I've instrumented the code a bit. So, with this change [moved in iio_verify_update() as Lars suggested]: root@analog:~# cd /sys/bus/iio/devices/iio\:device3/buffer root@analog:/sys/bus/iio/devices/iio:device3/buffer# echo 1 > enable 000000000 iio_verify_update 748 indio_dev->masklength 2 *insert_buffer->scan_mask 00000000 11111111 iio_verify_update 753 222222 __iio_update_buffers 1115 ret -22 333333333 iio_buffer_store_enable 1241 ret -22 -bash: echo: write error: Invalid argument so, 11111111, 222222 & 333333333 are all error paths. Without the patch: root@analog:~# cd /sys/bus/iio/devices/iio\:device3/buffer root@analog:/sys/bus/iio/devices/iio:device3/buffer# echo 1 > enable 000000000 iio_verify_update 748 indio_dev->masklength 2 *insert_buffer->scan_mask 00000000 root@analog:/sys/bus/iio/devices/iio:device3/buffer# no error path is hit; error paths are still there, but the bitmap_empty() check removed; So, buffer gets enabled, but scan_mask is empty. Will follow-up a V2 on this and attach this information. > > > > i caught this one while diff-ing the upstream & ADI trees, and i needed to > > dig a > > bit more into the ADI git history on it; > > > > i was a bit puzzled for a while, because some rework patches were upstreamed > > without this patch: > > > > https://lore.kernel.org/linux-iio/55585CAA.6000506@xxxxxxxxxx/ > > https://lore.kernel.org/linux-iio/5560685A.5060504@xxxxxxxxxx/ > > > > i also did not find any discussions/upstream attempt for this patch > > particularly > > > > so, it was easier for me just to RFC this > > > > > > > > > drivers/iio/industrialio-buffer.c | 6 ++++++ > > > > 1 file changed, 6 insertions(+) > > > > > > > > diff --git a/drivers/iio/industrialio-buffer.c > > > > b/drivers/iio/industrialio- > > > > buffer.c > > > > index 4ada5592aa2b..f222a118d0d3 100644 > > > > --- a/drivers/iio/industrialio-buffer.c > > > > +++ b/drivers/iio/industrialio-buffer.c > > > > @@ -1031,6 +1031,12 @@ static int __iio_update_buffers(struct iio_dev > > > > *indio_dev, > > > > return ret; > > > > > > > > if (insert_buffer) { > > > > + if (bitmap_empty(insert_buffer->scan_mask, > > > > + indio_dev->masklength)) { > > > > + ret = -EINVAL; > > > > + goto err_free_config; > > > > + } > > > > > > Since the check is so simple it might make sense to do it as the very > > > first thing before iio_verify_update(). > > > > works for me; > > > > > > > > > + > > > > ret = iio_buffer_request_update(indio_dev, > > > > insert_buffer); > > > > if (ret) > > > > goto err_free_config; > > > >
