Re: [PATCH v2 2/2] media: imx335: Fix reset-gpio handling

[Kieran Bingham <kieran.bingham@ideasonboard.com>]

Quoting Umang Jain (2024-07-31 06:41:35)
> Hi all,
> 
> On 30/07/24 2:40 pm, Laurent Pinchart wrote:
> > On Tue, Jul 30, 2024 at 10:42:01AM +0200, Krzysztof Kozlowski wrote:
> >> On 30/07/2024 10:24, Sakari Ailus wrote:
> >>> Hi Krzysztof,
> >>>
> >>> On Mon, Jul 29, 2024 at 04:09:39PM +0200, Krzysztof Kozlowski wrote:
> >>>> On 29/07/2024 13:04, Umang Jain wrote:
> >>>>> Rectify the logical value of reset-gpio so that it is set to
> >>>>> 0 (disabled) during power-on and to 1 (enabled) during power-off.
> >>>>>
> >>>>> Meanwhile at it, set the reset-gpio to GPIO_OUT_HIGH at initialization
> >>>>> time to make sure it starts off in reset.
> >>>>>
> >>>>> Fixes: 45d19b5fb9ae ("media: i2c: Add imx335 camera sensor driver")
> >>>>> Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
> >>>>> ---
> >>>>>   drivers/media/i2c/imx335.c | 8 ++++----
> >>>>>   1 file changed, 4 insertions(+), 4 deletions(-)
> >>>>>
> >>>> This will break all the users, so no. At least not without mentioning
> >>>> ABI break and some sort of investigating how customers or users are
> >>>> affected.
> >>> I know the original authors aren't using the driver anymore and it took
> >>> quite a bit of time until others started to contribute to it so I suspect
> >>> the driver hasn't been in use for that long. There are no instances of the
> >>> device in the in-kernel DTS either.
> >>>
> >>> Any DTS author should have also noticed the issue but of course there's a
> >>> risk someone could have just changed the polarity and not bothered to chech
> >>> what it was supposed to be.
> >>>
> >>> I agree the commit message should be more vocal about the effects on
> >>> existing DTS.
> >> I can imagine that all users (out of tree, in this case) inverted
> >> polarity in DTS based on what's implemented. You could go with some
> >> trivial hack, like I did for one of codecs - see 738455858a2d ("ASoC:
> >> codecs: wsa881x: Use proper shutdown GPIO polarity"), but I remember
> >> Mark Brown rejected similar commit for newer drivers.
> > I don't think there's any out-of-tree user, because when we started
> > using the recently driver, it required lots of fixes to even work at
> > all. I'll let Kieran and Umang comment on that, I haven't follow the
> > development in details.
> 
> indeed, initially we had to put up fixes like :
> 
> 14a60786d72e ("media: imx335: Set reserved register to default value")
> 81495a59baeba ("media: imx335: Fix active area height discrepency")
> 
> to make the sensor work properly on our platforms. Only after that we 
> had a base to support more capabilities on the sensor (multiple lanes 
> support, flips, TPG etc.)

I would also add that we had to provide control for the regulators to be
able to power the device as well in fea91ee73b7c ("media: i2c: imx335:
Enable regulator supplies").

Given the driver was posted from Intel, I would have anticipated perhaps
the driver was in fact only actually tested by Intel on ACPI platforms -
yet with no ACPI table registered in the driver - even that could likely
be considered broken.

Based on that I have a high confidence that there are no current users
of this driver (except us).

Umang, I see we need an updated patch with commit message to cover this,
please consider the above to add in there too.
--
Kieran