Re: [PATCH v1 1/3] media: ti: cal: Add support for 1X16 mbus formats

[Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>]

On 23/02/2023 19:10, Jacopo Mondi wrote:
> Hi Tomi
> 
> On Wed, Feb 22, 2023 at 02:56:28PM +0200, Tomi Valkeinen wrote:
>> For legacy reasons the CAL driver uses 2X8 mbus formats for the CSI-2
>> link (e.g. MEDIA_BUS_FMT_YUYV8_2X8). 1X16 formats are more correct and
>> used by many drivers, so add 1X16 support to CAL.
>>
>> We keep the 2X8 formats for backward compatibility.
> 
> Eh, this is the usual question about what we should consider a
> to be a userspace breakage or not.
> 
> I presume the reason to maintain 2X8 formats is (assuming the CAL
> interface is CSI-2 only, right ?) because sensor drivers that only
> support 2X8 formats will then fail to link_validate() if you remove

Yes.

> all 2X8 formats here. I'm of the opinion that we should bite the
> bullet and move to 1X16. If any driver that used to work with CAL now
> breaks, the sensor driver will have to be fixed.
> 
> In my humble experience, that's what we did with the ov5640 sensor. We

Yes, you did.

> removed the 2X8 formats in CSI-2 mode and some platform driver broke
> and then had been fixed (it happened in the same release cycle), win win.

No, CAL is still broken =). OV5640 is the only sensor I have. I just 
haven't had time to look at this and fix it (and no one has complained).

> I know it's controversial, let's see what others think.

I'm all for dropping the 2X8 formats, if that's the consensus. It would 
keep the driver simpler, as we could keep the 1:1 relationship between 
pixel formats and mbus codes.

I'll look at your other comments tomorrow.

  Tomi