Re: [PATCH v4 2/2] media: i2c: add Himax HM1246 image sensor driver

[Matthias Fend <matthias.fend@emfend.at>]

Hi Sakari,

Am 23.10.2025 um 11:00 schrieb Matthias Fend:
> Hi Sakari,
> 
> thanks a lot for your feedback.

I had two follow-up questions regarding your feedback, but I suspect 
they got lost in all the code. I've cleaned up this mail a bit to make 
the questions more visible.

>>> +
>>> +static int hm1246_update_controls(struct hm1246 *hm1246,
>>> +                  const struct hm1246_mode *mode)
>>> +{
>>> +    s64 pixel_rate, exposure_max, vblank, hblank;
>>> +    int ret;
>>> +
>>> +    ret = __v4l2_ctrl_s_ctrl(hm1246->link_freq_ctrl, mode- 
>>> >link_freq_index);
>>
>> Does this do something? There's only a single link frequency value (and
>> index) supported.
> 
> You're right. Even though hm1246_update_controls() isn't exactly wrong, 
> I could currently remove this function completely. The sensor supports 
> various modes (which result in different clock rates), and I've already 
> started implementing more of them. With multiple modes the controls need 
> to be updated. However, since there were still some internal sensor 
> issues to be addressed and I haven't been able to fully test them, I've 
> decided to use only the presumably most common RAW mode for now.
> 
> Should I remove the function now and add it back once more modes are 
> implemented?
> 
...
>>> +static int hm1246_parse_fwnode(struct hm1246 *hm1246)
>>> +{
>>> +    struct fwnode_handle *endpoint;
>>> +    struct v4l2_fwnode_endpoint bus_cfg = {
>>> +        .bus_type = V4L2_MBUS_PARALLEL,
>>> +    };
>>> +    int ret;
>>> +
>>> +    endpoint = fwnode_graph_get_endpoint_by_id(dev_fwnode(hm1246- 
>>> >dev), 0,
>>> +                           0,
>>> +                           FWNODE_GRAPH_ENDPOINT_NEXT);
>>> +    if (!endpoint)
>>> +        return dev_err_probe(hm1246->dev, -EINVAL,
>>> +                     "missing endpoint node\n");
>>> +
>>> +    ret = v4l2_fwnode_endpoint_parse(endpoint, &bus_cfg);
>>
>> What about validating the link frequencies? You can use
>> v4l2_link_freq_to_bitmap(), too.
> 
> I was under the impression that for sensors with a parallel interface, 
> no frequency information is provided in the device tree (because there's 
> no need for it). Since there are no frequency entries, they can't be 
> verified.
> 
> Am I wrong, or did you perhaps mean something else?
> 
Thanks
  ~Matthias