Re: [PATCH 2/2] media: ov9282: enable single-read I2C transactions

[Richard Leitner <richard.leitner@linux.dev>]

On Tue, Jul 21, 2026 at 06:58:22PM +0300, Laurent Pinchart wrote:
> On Tue, Jul 21, 2026 at 05:44:21PM +0200, Richard Leitner wrote:
> > Hi Laurent,
> > 
> > thank you very much for your quick feedback!
> > 
> > On Tue, Jul 21, 2026 at 06:16:14PM +0300, Laurent Pinchart wrote:
> > > On Tue, Jul 21, 2026 at 02:39:46PM +0100, Dave Stevenson wrote:
> > > > On Tue, 21 Jul 2026 at 14:25, Richard Leitner wrote:
> > > > >
> > > > > Some OV9282 camera modules, such as those from Vision Components, fail
> > > > > multi-byte register reads with the default CCI I2C regmap access pattern
> > > > > and only work when single-register read transactions are used. This
> > > > > results in the driver being unable to probe due to a chip id mismatch.
> > > > 
> > > > Those damn stupid Vision Components modules with the MCU that prevents
> > > > you reading registers.
> > > 
> > > There's good news, the situation is improving with recent modules. We
> > > still have to handle the other ones of course.
> > > 
> > > > I seem to recall Laurent had a plan for how to handle those without
> > > > having to patch all the drivers, however I can't find that thread
> > > > quickly.
> > > 
> > > I'm thinking of two options:
> > > 
> > > - We can introduce a new standard DT property for I2C device that will
> > >   be parsed by regmap or the I2C core directly, and switch to single
> > >   reads.
> > > 
> > > - We could model the MCU as some sort of I2C mux, sitting in DT between
> > >   the I2C controller and the image sensor, and translate multi-byte
> > >   reads to single-byte reads in that driver.
> > 
> > I'm basically fine with both. Personally I would prefer the first
> > option, as this would be a generic approach which other devices could also
> > use. Furthermore it's IMHO the simpler solution. But that's just my 2 cents.
> 
> The next step is to then write and send an RFC, to get feedback on the
> idea from the DT and I2C maintainers (and possibly regmap, if we handle
> the quirk at that level). Is that something you could work on ?

Sure. I'll take a more detailled look at it tomorrow.

regards;rl

...

> -- 
> Regards,
> 
> Laurent Pinchart