Re: [PATCH v14 04/11] media: uvcvideo: Split uvc_control_mapping.size to v4l2 and data size

Yunke Cao
2023-12-12T08:00:13Z

Hi Laurent,

Thanks for the review!

On Fri, Dec 8, 2023 at 11:15 PM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Yunke,
>
> Thank you for the patch.
>
> On Fri, Dec 01, 2023 at 04:18:55PM +0900, Yunke Cao wrote:
> > Rename the existing size to data_size to represent uvc control data size,
> > add a separate field for v4l2 control size. v4l2 control size will be
> > used the compound controls.
>
> s/uvc/UVC/ and s/v4l2/V4L2/ in the whole commit message.
>
> > Also modify the uvc driver documents to clarify the size in
> > uvc_xu_control_mapping corresponds to the uvc control data size.
> >
> > Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
> > Signed-off-by: Yunke Cao <yunkec@google.com>
> > ---
> > Changelog since v11:
> > - No change.
> > Changelog since v10:
> > - Added Reviewed-by from Daniel Scally.
> > Changelog since v9:
> > - No change.
> > Changelog since v8:
> > - No change.
> > Changelog since v7:
> > - Newly added patch.
> >
> > .../userspace-api/media/drivers/uvcvideo.rst | 2 +-
> > drivers/media/usb/uvc/uvc_ctrl.c | 80 +++++++++----------
> > drivers/media/usb/uvc/uvc_v4l2.c | 2 +-
> > drivers/media/usb/uvc/uvcvideo.h | 6 +-
> > 4 files changed, 47 insertions(+), 43 deletions(-)
> >
> > diff --git a/Documentation/userspace-api/media/drivers/uvcvideo.rst b/Documentation/userspace-api/media/drivers/uvcvideo.rst
> > index a290f9fadae9..aab4304e6bb5 100644
> > --- a/Documentation/userspace-api/media/drivers/uvcvideo.rst
> > +++ b/Documentation/userspace-api/media/drivers/uvcvideo.rst
> > @@ -157,7 +157,7 @@ Argument: struct uvc_xu_control_mapping
> > __u8 name[32] V4L2 control name
> > __u8 entity[16] UVC extension unit GUID
> > __u8 selector UVC control selector
> > - __u8 size V4L2 control size (in bits)
> > + __u8 size UVC control data size (in bits)
>
> The V4L2 and UVC sizes are identical for all controls mapped through
> this mechanism, right ?
>

Yes, I think that's right in the current implementation.
Do you think we need to support UVCIOC_CTRL_MAP for the compound controls?

I wanted to change this because simply we assign
+ map->data_size = xmap->size;
in uvc_ioctl_xu_ctrl_map().

Is this okay?

> > __u8 offset V4L2 control offset (in bits)
>
> If the size if the "UVC control data size", shouldn't this be the "UVC
> control data offset" ?
>

Ah, right. I will change this in the v15 if we keep the "UVC control data size".

> > enum v4l2_ctrl_type
> > v4l2_type V4L2 control type
> > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > index 4a685532f7eb..98254b93eb46 100644
> > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > @@ -464,7 +464,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_BRIGHTNESS,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_BRIGHTNESS_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_SIGNED,
> > @@ -473,7 +473,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_CONTRAST,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_CONTRAST_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_UNSIGNED,
> > @@ -482,7 +482,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_HUE,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_HUE_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_SIGNED,
> > @@ -493,7 +493,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_SATURATION,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_SATURATION_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_UNSIGNED,
> > @@ -502,7 +502,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_SHARPNESS,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_SHARPNESS_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_UNSIGNED,
> > @@ -511,7 +511,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_GAMMA,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_GAMMA_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_UNSIGNED,
> > @@ -520,7 +520,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_BACKLIGHT_COMPENSATION,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_BACKLIGHT_COMPENSATION_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_UNSIGNED,
> > @@ -529,7 +529,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_GAIN,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_GAIN_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_UNSIGNED,
> > @@ -538,7 +538,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_HUE_AUTO,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_HUE_AUTO_CONTROL,
> > - .size = 1,
> > + .data_size = 1,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_BOOLEAN,
> > .data_type = UVC_CTRL_DATA_TYPE_BOOLEAN,
> > @@ -548,7 +548,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_EXPOSURE_AUTO,
> > .entity = UVC_GUID_UVC_CAMERA,
> > .selector = UVC_CT_AE_MODE_CONTROL,
> > - .size = 4,
> > + .data_size = 4,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_MENU,
> > .data_type = UVC_CTRL_DATA_TYPE_BITMASK,
> > @@ -561,7 +561,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_EXPOSURE_AUTO_PRIORITY,
> > .entity = UVC_GUID_UVC_CAMERA,
> > .selector = UVC_CT_AE_PRIORITY_CONTROL,
> > - .size = 1,
> > + .data_size = 1,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_BOOLEAN,
> > .data_type = UVC_CTRL_DATA_TYPE_BOOLEAN,
> > @@ -570,7 +570,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_EXPOSURE_ABSOLUTE,
> > .entity = UVC_GUID_UVC_CAMERA,
> > .selector = UVC_CT_EXPOSURE_TIME_ABSOLUTE_CONTROL,
> > - .size = 32,
> > + .data_size = 32,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_UNSIGNED,
> > @@ -581,7 +581,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_AUTO_WHITE_BALANCE,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_WHITE_BALANCE_TEMPERATURE_AUTO_CONTROL,
> > - .size = 1,
> > + .data_size = 1,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_BOOLEAN,
> > .data_type = UVC_CTRL_DATA_TYPE_BOOLEAN,
> > @@ -591,7 +591,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_WHITE_BALANCE_TEMPERATURE,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_WHITE_BALANCE_TEMPERATURE_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_UNSIGNED,
> > @@ -602,7 +602,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_AUTO_WHITE_BALANCE,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_WHITE_BALANCE_COMPONENT_AUTO_CONTROL,
> > - .size = 1,
> > + .data_size = 1,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_BOOLEAN,
> > .data_type = UVC_CTRL_DATA_TYPE_BOOLEAN,
> > @@ -613,7 +613,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_BLUE_BALANCE,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_WHITE_BALANCE_COMPONENT_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_SIGNED,
> > @@ -624,7 +624,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_RED_BALANCE,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_WHITE_BALANCE_COMPONENT_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 16,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_SIGNED,
> > @@ -635,7 +635,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_FOCUS_ABSOLUTE,
> > .entity = UVC_GUID_UVC_CAMERA,
> > .selector = UVC_CT_FOCUS_ABSOLUTE_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_UNSIGNED,
> > @@ -646,7 +646,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_FOCUS_AUTO,
> > .entity = UVC_GUID_UVC_CAMERA,
> > .selector = UVC_CT_FOCUS_AUTO_CONTROL,
> > - .size = 1,
> > + .data_size = 1,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_BOOLEAN,
> > .data_type = UVC_CTRL_DATA_TYPE_BOOLEAN,
> > @@ -656,7 +656,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_IRIS_ABSOLUTE,
> > .entity = UVC_GUID_UVC_CAMERA,
> > .selector = UVC_CT_IRIS_ABSOLUTE_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_UNSIGNED,
> > @@ -665,7 +665,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_IRIS_RELATIVE,
> > .entity = UVC_GUID_UVC_CAMERA,
> > .selector = UVC_CT_IRIS_RELATIVE_CONTROL,
> > - .size = 8,
> > + .data_size = 8,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_SIGNED,
> > @@ -674,7 +674,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_ZOOM_ABSOLUTE,
> > .entity = UVC_GUID_UVC_CAMERA,
> > .selector = UVC_CT_ZOOM_ABSOLUTE_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_UNSIGNED,
> > @@ -683,7 +683,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_ZOOM_CONTINUOUS,
> > .entity = UVC_GUID_UVC_CAMERA,
> > .selector = UVC_CT_ZOOM_RELATIVE_CONTROL,
> > - .size = 0,
> > + .data_size = 0,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_SIGNED,
> > @@ -694,7 +694,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_PAN_ABSOLUTE,
> > .entity = UVC_GUID_UVC_CAMERA,
> > .selector = UVC_CT_PANTILT_ABSOLUTE_CONTROL,
> > - .size = 32,
> > + .data_size = 32,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_SIGNED,
> > @@ -703,7 +703,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_TILT_ABSOLUTE,
> > .entity = UVC_GUID_UVC_CAMERA,
> > .selector = UVC_CT_PANTILT_ABSOLUTE_CONTROL,
> > - .size = 32,
> > + .data_size = 32,
> > .offset = 32,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_SIGNED,
> > @@ -712,7 +712,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_PAN_SPEED,
> > .entity = UVC_GUID_UVC_CAMERA,
> > .selector = UVC_CT_PANTILT_RELATIVE_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_SIGNED,
> > @@ -723,7 +723,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_TILT_SPEED,
> > .entity = UVC_GUID_UVC_CAMERA,
> > .selector = UVC_CT_PANTILT_RELATIVE_CONTROL,
> > - .size = 16,
> > + .data_size = 16,
> > .offset = 16,
> > .v4l2_type = V4L2_CTRL_TYPE_INTEGER,
> > .data_type = UVC_CTRL_DATA_TYPE_SIGNED,
> > @@ -734,7 +734,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_PRIVACY,
> > .entity = UVC_GUID_UVC_CAMERA,
> > .selector = UVC_CT_PRIVACY_CONTROL,
> > - .size = 1,
> > + .data_size = 1,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_BOOLEAN,
> > .data_type = UVC_CTRL_DATA_TYPE_BOOLEAN,
> > @@ -743,7 +743,7 @@ static const struct uvc_control_mapping uvc_ctrl_mappings[] = {
> > .id = V4L2_CID_PRIVACY,
> > .entity = UVC_GUID_EXT_GPIO_CONTROLLER,
> > .selector = UVC_CT_PRIVACY_CONTROL,
> > - .size = 1,
> > + .data_size = 1,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_BOOLEAN,
> > .data_type = UVC_CTRL_DATA_TYPE_BOOLEAN,
> > @@ -754,7 +754,7 @@ const struct uvc_control_mapping uvc_ctrl_power_line_mapping_limited = {
> > .id = V4L2_CID_POWER_LINE_FREQUENCY,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_POWER_LINE_FREQUENCY_CONTROL,
> > - .size = 2,
> > + .data_size = 2,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_MENU,
> > .data_type = UVC_CTRL_DATA_TYPE_ENUM,
> > @@ -766,7 +766,7 @@ const struct uvc_control_mapping uvc_ctrl_power_line_mapping_uvc11 = {
> > .id = V4L2_CID_POWER_LINE_FREQUENCY,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_POWER_LINE_FREQUENCY_CONTROL,
> > - .size = 2,
> > + .data_size = 2,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_MENU,
> > .data_type = UVC_CTRL_DATA_TYPE_ENUM,
> > @@ -783,7 +783,7 @@ static const struct uvc_control_mapping uvc_ctrl_power_line_mapping_uvc15 = {
> > .id = V4L2_CID_POWER_LINE_FREQUENCY,
> > .entity = UVC_GUID_UVC_PROCESSING,
> > .selector = UVC_PU_POWER_LINE_FREQUENCY_CONTROL,
> > - .size = 2,
> > + .data_size = 2,
> > .offset = 0,
> > .v4l2_type = V4L2_CTRL_TYPE_MENU,
> > .data_type = UVC_CTRL_DATA_TYPE_ENUM,
> > @@ -816,7 +816,7 @@ static inline void uvc_clear_bit(u8 *data, int bit)
> > }
> >
> > /*
> > - * Extract the bit string specified by mapping->offset and mapping->size
> > + * Extract the bit string specified by mapping->offset and mapping->data_size
> > * from the little-endian data stored at 'data' and return the result as
> > * a signed 32bit integer. Sign extension will be performed if the mapping
> > * references a signed data type.
> > @@ -824,7 +824,7 @@ static inline void uvc_clear_bit(u8 *data, int bit)
> > static s32 uvc_get_le_value(struct uvc_control_mapping *mapping,
> > u8 query, const u8 *data)
> > {
> > - int bits = mapping->size;
> > + int bits = mapping->data_size;
> > int offset = mapping->offset;
> > s32 value = 0;
> > u8 mask;
> > @@ -847,19 +847,19 @@ static s32 uvc_get_le_value(struct uvc_control_mapping *mapping,
> >
> > /* Sign-extend the value if needed. */
> > if (mapping->data_type == UVC_CTRL_DATA_TYPE_SIGNED)
> > - value |= -(value & (1 << (mapping->size - 1)));
> > + value |= -(value & (1 << (mapping->data_size - 1)));
> >
> > return value;
> > }
> >
> > /*
> > - * Set the bit string specified by mapping->offset and mapping->size
> > + * Set the bit string specified by mapping->offset and mapping->data_size
> > * in the little-endian data stored at 'data' to the value 'value'.
> > */
> > static void uvc_set_le_value(struct uvc_control_mapping *mapping,
> > s32 value, u8 *data)
> > {
> > - int bits = mapping->size;
> > + int bits = mapping->data_size;
> > int offset = mapping->offset;
> > u8 mask;
> >
> > @@ -2039,7 +2039,7 @@ int uvc_ctrl_set(struct uvc_fh *handle,
> > * needs to be loaded from the device to perform the read-modify-write
> > * operation.
> > */
> > - if ((ctrl->info.size * 8) != mapping->size) {
> > + if ((ctrl->info.size * 8) != mapping->data_size) {
> > ret = __uvc_ctrl_load_cur(chain, ctrl);
> > if (ret < 0)
> > return ret;
> > @@ -2546,8 +2546,8 @@ int uvc_ctrl_add_mapping(struct uvc_video_chain *chain,
> > }
> >
> > /* Validate the user-provided bit-size and offset */
> > - if (mapping->size > 32 ||
> > - mapping->offset + mapping->size > ctrl->info.size * 8) {
> > + if (mapping->data_size > 32 ||
> > + mapping->offset + mapping->data_size > ctrl->info.size * 8) {
> > ret = -EINVAL;
> > goto done;
> > }
> > diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> > index 5a88847bfbfe..ff72caf7bc9e 100644
> > --- a/drivers/media/usb/uvc/uvc_v4l2.c
> > +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> > @@ -122,7 +122,7 @@ static int uvc_ioctl_xu_ctrl_map(struct uvc_video_chain *chain,
> > }
> > memcpy(map->entity, xmap->entity, sizeof(map->entity));
> > map->selector = xmap->selector;
> > - map->size = xmap->size;
> > + map->data_size = xmap->size;
> > map->offset = xmap->offset;
> > map->v4l2_type = xmap->v4l2_type;
> > map->data_type = xmap->data_type;
> > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> > index 5091085fcfb0..7bc41270ed94 100644
> > --- a/drivers/media/usb/uvc/uvcvideo.h
> > +++ b/drivers/media/usb/uvc/uvcvideo.h
> > @@ -110,7 +110,11 @@ struct uvc_control_mapping {
> > u8 entity[16];
> > u8 selector;
> >
> > - u8 size;
> > + /* Size of the v4l2 control. Required for compound controls. */
> > + u8 v4l2_size;
>
> Let's introduce this field in the patch that uses it. The commit message
> needs to be updated to explain that this patch renames the size field to
> data_size to prepare for adding another size field for compound
> controls.
>

Sounds good.

> > + /* UVC data size. Required for all controls. */
>
> "UVC data size" is not very clear. Let me attempt to write a more
> precise description:
>
> /*
> * Size of the control data in the payload of the UVC control GET and
> * SET requests, expressed in bits.
> */
>
> Is this correct ?
>

Yes, that sounds much better indeed.

Best,
Yunke

> > + u8 data_size;
> > +
> > u8 offset;
> > enum v4l2_ctrl_type v4l2_type;
> > u32 data_type;
>
> --
> Regards,
>
> Laurent Pinchart