Re: [PATCH v15 01/32] v4l: async: Remove re-probing support

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Hi Mauro,

On Mon, Oct 09, 2017 at 08:22:39AM -0300, Mauro Carvalho Chehab wrote:
> Em Thu,  5 Oct 2017 00:50:20 +0300
> Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> escreveu:
> 
> > Remove V4L2 async re-probing support. The re-probing support has been
> > there to support cases where the sub-devices require resources provided by
> > the main driver's hardware to function, such as clocks.
> > 
> > Reprobing has allowed unbinding and again binding the main driver without
> > explicilty unbinding the sub-device drivers. This is certainly not a
> > common need, and the responsibility will be the user's going forward.
> > 
> > An alternative could have been to introduce notifier specific locks.
> > Considering the complexity of the re-probing and that it isn't really a
> > solution to a problem but a workaround, remove re-probing instead.
> 
> If the re-probing isn't using anywhere, that sounds a nice cleanup.
> Did you check if this won't break any driver (like soc_camera)?

That was discussed earlier in the review; Laurent asked the same question.

Re-probing never was a proper solution to any problem; it was just a hack
to avoid unbinding the sensor if the bridge driver was unbound, no more: it
can't be generalised to support more complex use cases. Mind you, this is
on devices that aren't actually removable.

I've briefly discussed this with Laurent; the proper solution would need to
be implemented in the clock framework instead. There, the existing clocks
obtained by drivers could be re-activated when the driver for them comes
back.

My proposal is that if there's real a need to address this, then it could
be solved in the clock framework.

-- 
Kind regards,

Sakari Ailus
e-mail: sakari.ailus@xxxxxx



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