Re: [PATCH v5] Driver for ON Semi AR0521 camera sensor

Jacopo Mondi [off-list ref] writes:

quoted

This is BTW completely orthogonal to the -EBUSY on set_fmt(). The
effects will be exactly the same if the e.g. geometry changes come when
the sensor is not streaming.

No, this isn't true. Your s_fmt() implementation stops then restart the
stream. It has an undocumented side effect and will cause undefined
behaviour.

It will cause *at*most* a corrupted frame. On a MIPI link. That's right.
Such a corrupted frame will *at*most* cause some transient IO error - it
must not cause anything serious, because corrupted frames on MIPI can
happen for multiple reasons, some of which simply cannot be avoided.
BTW I will see if it's actually the case - chances are, there is no
corruption, but I tested it years ago and haven't yet checked my notes.

In fact those set_fmt() in other drivers may - or may not - cause
corrupted frames just the same.

If your s_fmt() has to stop and restart streaming to take effect,
it means userspace should instead stop the stream, change
the format where opportune in the pipeline, and then restart the
stream.

Maybe. This is a sensor driver - not userspace.
If the userspace uses it as a part of "frame grabber", it will certainly
do exactly that (nothing else would make sense in practice).

Unfortunately this all will have to wait a bit, so thanks for your help,
expect a new patch in few weeks.
-- 
Krzysztof "Chris" Hałasa

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