linux-kernel - Re: [PATCH v2 10/12] media: uvcvideo: Add get_* functions to uvc

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Message-ID: <7c9306c4-1897-41be-b2c1-cb98166ba51a@kernel.org>
Date: Mon, 14 Jul 2025 16:28:43 +0200
From: Hans de Goede <hansg@...nel.org>
To: Ricardo Ribalda <ribalda@...omium.org>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Hans de Goede <hdegoede@...hat.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>, Hans Verkuil
 <hverkuil@...all.nl>, Sakari Ailus <sakari.ailus@...ux.intel.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Linus Walleij
 <linus.walleij@...aro.org>, Bartosz Golaszewski <brgl@...ev.pl>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
 linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
 linux-gpio@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v2 10/12] media: uvcvideo: Add get_* functions to
 uvc_entity

Hi Ricardo, Laurent,

On 1-Jul-25 13:13, Ricardo Ribalda wrote:
> Hi Laurent
> 
> On Sun, 29 Jun 2025 at 20:13, Laurent Pinchart
> <laurent.pinchart@...asonboard.com> wrote:
>>
>> Hi Ricardo,
>>
>> Thank you for the patch.
>>
>> On Thu, Jun 05, 2025 at 05:53:03PM +0000, Ricardo Ribalda wrote:
>>> Virtual entities need to provide more values than get_cur and get_cur
>>
>> I think you meant "get_info and get_cur".
>>
>>> for their controls. Add support for get_def, get_min, get_max and
>>> get_res.
>>
>> Do they ? The UVC specification defines controls that don't list
>> GET_DEF, GET_MIN, GET_MAX and GET_RES as mandatory requests. Can't we do
>> the same for the software controls ? This patch is meant to support the
>> UVC_SWENTITY_ORIENTATION and UVC_SWENTITY_ROTATION control in the next
>> patch, and those are read-only controls. Aren't GET_INFO and GET_CUR
>> enough ?
> 
> V4L2_CID_CAMERA_ROTATION has the type UVC_CTRL_DATA_TYPE_UNSIGNED,
> that time requires get_min and get_max.
> We can create a new type UVC_CTRL_DATA_TYPE_UNSIGNED_READ_ONLY that
> fakes min, max and res, but I think that it is cleaner this approach.

If I read this right, then we could at least drop adding get_def and
get_res callbacks from this patch, right?

Can you do that for the next version please?

Regards,

Hans




>>> This is a preparation patch.
>>>
>>> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
>>> ---
>>>  drivers/media/usb/uvc/uvc_ctrl.c | 12 ++++++++++++
>>>  drivers/media/usb/uvc/uvcvideo.h |  8 ++++++++
>>>  2 files changed, 20 insertions(+)
>>>
>>> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
>>> index 21ec7b978bc7aca21db7cb8fd5d135d876f3330c..59be62ae24a4219fa9d7aacf2ae7382c95362178 100644
>>> --- a/drivers/media/usb/uvc/uvc_ctrl.c
>>> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
>>> @@ -596,6 +596,18 @@ static int uvc_ctrl_query_entity(struct uvc_device *dev,
>>>       if (query == UVC_GET_CUR && ctrl->entity->get_cur)
>>>               return ctrl->entity->get_cur(dev, ctrl->entity,
>>>                                            ctrl->info.selector, data, len);
>>> +     if (query == UVC_GET_DEF && ctrl->entity->get_def)
>>> +             return ctrl->entity->get_def(dev, ctrl->entity,
>>> +                                          ctrl->info.selector, data, len);
>>> +     if (query == UVC_GET_MIN && ctrl->entity->get_min)
>>> +             return ctrl->entity->get_min(dev, ctrl->entity,
>>> +                                          ctrl->info.selector, data, len);
>>> +     if (query == UVC_GET_MAX && ctrl->entity->get_max)
>>> +             return ctrl->entity->get_max(dev, ctrl->entity,
>>> +                                          ctrl->info.selector, data, len);
>>> +     if (query == UVC_GET_RES && ctrl->entity->get_res)
>>> +             return ctrl->entity->get_res(dev, ctrl->entity,
>>> +                                          ctrl->info.selector, data, len);
>>>       if (query == UVC_GET_INFO && ctrl->entity->get_info)
>>>               return ctrl->entity->get_info(dev, ctrl->entity,
>>>                                             ctrl->info.selector, data);
>>> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
>>> index a931750bdea25b9062dcc7644bf5f2ed89c1cb4c..d6da8ed3ad4cf3377df49923e051fe04d83d2e38 100644
>>> --- a/drivers/media/usb/uvc/uvcvideo.h
>>> +++ b/drivers/media/usb/uvc/uvcvideo.h
>>> @@ -261,6 +261,14 @@ struct uvc_entity {
>>>                       u8 cs, u8 *caps);
>>>       int (*get_cur)(struct uvc_device *dev, struct uvc_entity *entity,
>>>                      u8 cs, void *data, u16 size);
>>> +     int (*get_def)(struct uvc_device *dev, struct uvc_entity *entity,
>>> +                    u8 cs, void *data, u16 size);
>>> +     int (*get_min)(struct uvc_device *dev, struct uvc_entity *entity,
>>> +                    u8 cs, void *data, u16 size);
>>> +     int (*get_max)(struct uvc_device *dev, struct uvc_entity *entity,
>>> +                    u8 cs, void *data, u16 size);
>>> +     int (*get_res)(struct uvc_device *dev, struct uvc_entity *entity,
>>> +                    u8 cs, void *data, u16 size);
>>>
>>>       unsigned int ncontrols;
>>>       struct uvc_control *controls;
>>
>> --
>> Regards,
>>
>> Laurent Pinchart
> 
> 
>