Re: [PATCH v4 2/2] iio: light: vcnl4000: add support for Capella CM36686 and CM36672P

[Erikas Bitovtas]

On 2/15/26 9:31 PM, Jonathan Cameron wrote:
> On Sun, 15 Feb 2026 19:28:56 +0200
> Erikas Bitovtas <xerikasxx@xxxxxxxxx> wrote:
> 
>> On 2/14/26 8:09 PM, Jonathan Cameron wrote:
>>>> ---
>>>>  drivers/iio/light/vcnl4000.c | 40 ++++++++++++++++++++++++++++++++++++++++
>>>>  1 file changed, 40 insertions(+)
>>>>
>>>> diff --git a/drivers/iio/light/vcnl4000.c b/drivers/iio/light/vcnl4000.c
>>>> index a36c23813679..1f8f4e4586f4 100644
>>>> --- a/drivers/iio/light/vcnl4000.c
>>>> +++ b/drivers/iio/light/vcnl4000.c
>>>> @@ -185,6 +185,7 @@ static const int vcnl4040_ps_oversampling_ratio[] = {1, 2, 4, 8};
>>>>  #define VCNL4000_SLEEP_DELAY_MS	2000 /* before we enter pm_runtime_suspend */
>>>>  
>>>>  enum vcnl4000_device_ids {
>>>> +	CM36672P,
>>>>  	VCNL4000,
>>>>  	VCNL4010,
>>>>  	VCNL4040,
>>>> @@ -235,6 +236,8 @@ struct vcnl4000_chip_spec {
>>>>  };
>>>>  
>>>>  static const struct i2c_device_id vcnl4000_id[] = {
>>>> +	{ "cm36672p", CM36672P },
>>>> +	{ "cm36686", VCNL4040 },
>>>>  	{ "vcnl4000", VCNL4000 },
>>>>  	{ "vcnl4010", VCNL4010 },
>>>>  	{ "vcnl4020", VCNL4010 },
>>>> @@ -1842,6 +1845,22 @@ static const struct iio_chan_spec vcnl4040_channels[] = {
>>>>  	}
>>>>  };  
>>>
>>> ...
>>>   
>>>>  	[VCNL4000] = {
>>>>  		.prod = "VCNL4000",
>>>>  		.init = vcnl4000_init,
>>>> @@ -2033,6 +2065,14 @@ static int vcnl4000_probe(struct i2c_client *client)
>>>>  }
>>>>  
>>>>  static const struct of_device_id vcnl_4000_of_match[] = {
>>>> +	{
>>>> +		.compatible = "capella,cm36672p",
>>>> +		.data = (void *)CM36672P,
>>>> +	},
>>>> +	{
>>>> +		.compatible = "capella,cm36686",
>>>> +		.data = (void *)VCNL4040,  
>>>
>>> Is this necessary? I 'think' if you drop it we'll match instead
>>> on the vcnl4040 fallback and then the access to the data will be
>>> through the stripped name only bit of the compatible (first entry, not
>>> the fallback so cm36686 in this case). So you do need the cm36686
>>> entry in the i2c_device_id table above. Probably better to keep
>>> this here to avoid having to reason this out - but perhaps a
>>> comment to that affect would be useful (assuming you verify my
>>> reasoning).
>>>  
>> After I removed the entry for "capella,cm36686", I received the "Unable
>> to handle kernel NULL pointer dereference" error in dmesg. And at least
>> stk3310 driver includes a compatible entry both for the device (stk3013)
>> and for the fallback (stk3310). So my assumption is that this entry is
>> needed.
>> I could include a comment explaining that cm36686 is fully compatible
>> with vcnl4040, however, if that is necessary.
> 
> Thanks for checking.
> 
> What did you get as the backtrace?  I'm hoping it'll explain what I'm
> misunderstanding!  The hacks around using the wrong table for compatible
> matches have tripped me up before.
> 
> Jonathan
> 

I am attaching a link to the dmesg. There were quite a lot of lines in
the stack trace and I am not sure what is the right way to post logs in
the mailing list.

https://pastebin.com/QgeTdNEP