On 23/03/2022 15:50, Sakari Ailus wrote:
> Hi Krysztof,
>
> On Sun, Mar 20, 2022 at 12:58:08PM +0100, Krzysztof Kozlowski wrote:
>> On 18/03/2022 17:51, Sakari Ailus wrote:
>>> There is firmware out there that uses "dongwoon,dw9807" compatible string
>>> that never made it to upstream as-is. Add it to the driver to make it load
>>> on such systems.
>>>
>>> The chip also has an EEPROM part which is AT24 compatible (for reading
>>> purposes) on a separate I²C address. Adding possible support for this in
>>> the future is not affected by this change.
>>>
>>> Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
>>> ---
>>> drivers/media/i2c/dw9807-vcm.c | 2 ++
>>> 1 file changed, 2 insertions(+)
>>>
>>> diff --git a/drivers/media/i2c/dw9807-vcm.c b/drivers/media/i2c/dw9807-vcm.c
>>> index 95e06f13bc9ed..ada8e467a0450 100644
>>> --- a/drivers/media/i2c/dw9807-vcm.c
>>> +++ b/drivers/media/i2c/dw9807-vcm.c
>>> @@ -295,6 +295,8 @@ static int __maybe_unused dw9807_vcm_resume(struct device *dev)
>>>
>>> static const struct of_device_id dw9807_of_table[] = {
>>> { .compatible = "dongwoon,dw9807-vcm" },
>>> + /* Compatibility for older firmware */
>>> + { .compatible = "dongwoon,dw9807" },
>>
>> You need to add it to the bindings as well.
>
> Why? Generally things that are there for binary compatibility but
> deprecated are not documented in bindings.
Because:
1. Otherwise it will get removed by someone as undocumented, unknown
stuff. Someone might treat it as mistake.
2. Putting it in the driver code is already self-documenting, so someone
might start using it. This should be clearly discouraged and bindings
help in it - the compatible is marked as deprecated with the comment you
mentioned.
3. Bindings are used beyond Linux kernel, so they might document
something more than we use here in DT.
Best regards,
Krzysztof
