Re: [RFC v3 04/19] media/usb/uvc: Implement vivioc_g_def_ext_ctrls

Hans Verkuil
2015-07-16T08:38:03Z

On 07/16/15 10:27, Laurent Pinchart wrote:
> On Thursday 16 July 2015 10:23:03 Hans Verkuil wrote:
>> On 07/16/15 10:11, Laurent Pinchart wrote:
>>> On Thursday 16 July 2015 09:38:11 Hans Verkuil wrote:
>>>> On 07/15/15 23:05, Laurent Pinchart wrote:
>>>>> On Friday 12 June 2015 18:46:23 Ricardo Ribalda Delgado wrote:
>>>>>> Callback needed by ioctl VIDIOC_G_DEF_EXT_CTRLS as this driver does not
>>>>>> use the controller framework.
>>>>>>
>>>>>> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
>>>>>> ---
>>>>>>
>>>>>> drivers/media/usb/uvc/uvc_v4l2.c | 30 ++++++++++++++++++++++++++++++
>>>>>> 1 file changed, 30 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c
>>>>>> b/drivers/media/usb/uvc/uvc_v4l2.c index 2764f43607c1..e2698a77138a
>>>>>> 100644
>>>>>> --- a/drivers/media/usb/uvc/uvc_v4l2.c
>>>>>> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
>>>>>> @@ -1001,6 +1001,35 @@ static int uvc_ioctl_g_ext_ctrls(struct file
>>>>>> *file, void *fh,
>>>>>> return uvc_ctrl_rollback(handle);
>>>>>> }
>>>>>>
>>>>>> +static int uvc_ioctl_g_def_ext_ctrls(struct file *file, void *fh,
>>>>>> + struct v4l2_ext_controls *ctrls)
>>>>>> +{
>>>>>> + struct uvc_fh *handle = fh;
>>>>>> + struct uvc_video_chain *chain = handle->chain;
>>>>>> + struct v4l2_ext_control *ctrl = ctrls->controls;
>>>>>> + unsigned int i;
>>>>>> + int ret;
>>>>>> + struct v4l2_queryctrl qc;
>>>>>> +
>>>>>> + ret = uvc_ctrl_begin(chain);
>>>>>
>>>>> There's no need to call uvc_ctrl_begin() here (and if there was, you'd
>>>>> have to call uvc_ctrl_rollback() or uvc_ctrl_commit() before returning).
>>>>>
>>>>>> + if (ret < 0)
>>>>>> + return ret;
>>>>>> +
>>>>>> + for (i = 0; i < ctrls->count; ++ctrl, ++i) {
>>>>>> + qc.id = ctrl->id;
>>>>>> + ret = uvc_query_v4l2_ctrl(chain, &qc);
>>>>>> + if (ret < 0) {
>>>>>> + ctrls->error_idx = i;
>>>>>> + return ret;
>>>>>> + }
>>>>>> + ctrl->value = qc.default_value;
>>>>>> + }
>>>>>> +
>>>>>> + ctrls->error_idx = 0;
>>>>>> +
>>>>>> + return 0;
>>>>>> +}
>>>>>
>>>>> Instead of open-coding this in multiple drivers, how about adding a
>>>>> helper function to the core ? Something like (totally untested)
>>>>
>>>> It's only open-coded in drivers that do not use the control framework.
>>>> For drivers that use the control framework it is completely transparent.
>>>
>>> Sure, but still, the same function is implemented several times while a
>>> single implementation could do. I'd prefer having it in the core until
>>> all (or all but one) drivers are converted to the control framework.
>>
>> There are only three drivers that need to implement this manually: uvc,
>> saa7164 and pvrusb2. That's not enough to warrant moving this into the
>> core.
>
> I'd argue that even just two drivers would be enough :-) Especially given that
> the proposed implementation for uvcvideo is wrong.

I don't want to add code to the core to cater to exceptions.

>> One of these days I should sit down and convert saa7164 to the control
>> framework. That shouldn't be too difficult.
>
> How about pvrusb2, is there a good reason not to use the control framework
> there ?

Brrr. pvrusb2 exports controls (and a bunch of other things) to /sys allowing
scripts to get/set controls using cat and echo. I have no idea how to switch pvrusb2
to the control framework while still keeping this non-standard API.

I guess one of these days I will need to look at it, but I've been postponing it
for years now :-)

There are still a few other drivers that do not use the control framework:

saa7164, zoran, fsl-viu, omap_vout (although I hope that one can be removed),
usbvision and bcm2048 (that's a staging driver, so I can probably ignore that one).

pvrusb2 is actually fairly important: v4l2-subdev still has legacy ops for handling
controls and as long as pvrusb2 is not converted I cannot remove those ops.

Regards,

Hans