Re: [PATCH v6 1/5] media: v4l2-core: add new control type V4L2_CTRL_TYPE_S8

[Deepa Guthyappa Madivalara <deepa.madivalara@oss.qualcomm.com>]

On 9/22/2026 6:17 AM, Hans Verkuil wrote:
> Hi Deepa,
>
> On 16/09/2026 00:00, Deepa Guthyappa Madivalara wrote:
>> Introduce V4L2_CTRL_TYPE_S8 (enum value 0x0103) as a new
>> control type for signed 8-bit values. Add necessary support in
>> v4l2_ext_control, v4l2_ctrl_ptr and handling in v4l2-ctrls-core,
>> v4l2-ctrls-api.
> One reason I asked you to split up adding the type and the control is
> that this makes it easy to do a 'git grep V4L2_CTRL_TYPE_U8' and compare
> that with 'git grep V4L2_CTRL_TYPE_S8' and see if the same number of changes
> is made in documentation, headers, and core code.
>
> And I see that S8 support is missing in v4l2_ctrl_type_op_validate() and
> check_range(), so that has to be added in a v7.
>
> Regards,
>
> 	Hans

Acknowledged, updated in v7.
Thanks
Deepa

>> Signed-off-by: Deepa Guthyappa Madivalara <deepa.madivalara@oss.qualcomm.com>
>> ---
>>   .../userspace-api/media/v4l/videodev2.h.rst.exceptions        |  1 +
>>   Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst  |  4 ++++
>>   Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst    |  6 ++++++
>>   drivers/media/v4l2-core/v4l2-ctrls-api.c                      |  1 +
>>   drivers/media/v4l2-core/v4l2-ctrls-core.c                     | 11 +++++++++++
>>   include/media/v4l2-ctrls.h                                    |  2 ++
>>   include/uapi/linux/videodev2.h                                |  2 ++
>>   7 files changed, 27 insertions(+)
>>
>> diff --git a/Documentation/userspace-api/media/v4l/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/v4l/videodev2.h.rst.exceptions
>> index 6182b4e2d2ee002c0d3562e1cc3bc2fd9c4286d6..b036ed3ec2f0744175cad1cbc4e73fe828e0c955 100644
>> --- a/Documentation/userspace-api/media/v4l/videodev2.h.rst.exceptions
>> +++ b/Documentation/userspace-api/media/v4l/videodev2.h.rst.exceptions
>> @@ -141,6 +141,7 @@ replace symbol V4L2_CTRL_TYPE_STRING :c:type:`V4L.v4l2_ctrl_type`
>>   replace symbol V4L2_CTRL_TYPE_U16 :c:type:`V4L.v4l2_ctrl_type`
>>   replace symbol V4L2_CTRL_TYPE_U32 :c:type:`V4L.v4l2_ctrl_type`
>>   replace symbol V4L2_CTRL_TYPE_U8 :c:type:`V4L.v4l2_ctrl_type`
>> +replace symbol V4L2_CTRL_TYPE_S8 :c:type:`V4L.v4l2_ctrl_type`
>>   replace symbol V4L2_CTRL_TYPE_MPEG2_SEQUENCE :c:type:`V4L.v4l2_ctrl_type`
>>   replace symbol V4L2_CTRL_TYPE_MPEG2_PICTURE :c:type:`V4L.v4l2_ctrl_type`
>>   replace symbol V4L2_CTRL_TYPE_MPEG2_QUANTISATION :c:type:`V4L.v4l2_ctrl_type`
>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst b/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
>> index d78328152b7552f8f0d30a9e2f7c104bfd4b70d3..fe5f8992389c32d8f35f432229ef2f734002644e 100644
>> --- a/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
>> +++ b/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
>> @@ -188,6 +188,10 @@ still cause this situation.
>>         - ``p_u32``
>>         - A pointer to a matrix control of unsigned 32-bit values. Valid if
>>   	this control is of type ``V4L2_CTRL_TYPE_U32``.
>> +    * - __s8 *
>> +      - ``p_s8``
>> +      - A pointer to a matrix control of signed 8-bit values. Valid if
>> +	this control is of type ``V4L2_CTRL_TYPE_S8``.
>>       * - __s32 *
>>         - ``p_s32``
>>         - A pointer to a matrix control of signed 32-bit values. Valid if
>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
>> index 82c8b52e771ce9301491b3f752e501a8fe7e2434..57e1652ae72e0324742142446acf32a16b94941c 100644
>> --- a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
>> +++ b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
>> @@ -425,6 +425,12 @@ See also the examples in :ref:`control`.
>>         - any
>>         - An unsigned 32-bit valued control ranging from minimum to maximum
>>   	inclusive. The step value indicates the increment between values.
>> +    * - ``V4L2_CTRL_TYPE_S8``
>> +      - any
>> +      - any
>> +      - any
>> +      - A signed 8-bit valued control ranging from minimum to maximum
>> +	inclusive. The step value indicates the increment between values.
>>       * - ``V4L2_CTRL_TYPE_MPEG2_QUANTISATION``
>>         - n/a
>>         - n/a
>> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-api.c b/drivers/media/v4l2-core/v4l2-ctrls-api.c
>> index 93d8d4012d0f4fef004e417d0aee2ae44b1b30bd..7d41cfd7378baaa929d4da0266c45f731bb54285 100644
>> --- a/drivers/media/v4l2-core/v4l2-ctrls-api.c
>> +++ b/drivers/media/v4l2-core/v4l2-ctrls-api.c
>> @@ -980,6 +980,7 @@ int __v4l2_ctrl_modify_range(struct v4l2_ctrl *ctrl,
>>   	case V4L2_CTRL_TYPE_U8:
>>   	case V4L2_CTRL_TYPE_U16:
>>   	case V4L2_CTRL_TYPE_U32:
>> +	case V4L2_CTRL_TYPE_S8:
>>   		if (ctrl->is_array)
>>   			return -EINVAL;
>>   		ret = check_range(ctrl->type, min, max, step, def);
>> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-core.c b/drivers/media/v4l2-core/v4l2-ctrls-core.c
>> index 9caca56478d1a97ccde582a2086e7039411b52ed..b78992e32e21c79b1c70ec673b81759c9ca84206 100644
>> --- a/drivers/media/v4l2-core/v4l2-ctrls-core.c
>> +++ b/drivers/media/v4l2-core/v4l2-ctrls-core.c
>> @@ -297,6 +297,9 @@ static void __v4l2_ctrl_type_op_init(const struct v4l2_ctrl *ctrl, u32 from_idx,
>>   			memset(ptr.p_u32 + from_idx, 0, elems * sizeof(u32));
>>   		}
>>   		break;
>> +	case V4L2_CTRL_TYPE_S8:
>> +		memset(ptr.p_s8 + from_idx, (u8)value, elems);
>> +		break;
>>   	default:
>>   		for (i = from_idx; i < tot_elems; i++) {
>>   			switch (which) {
>> @@ -377,6 +380,9 @@ void v4l2_ctrl_type_op_log(const struct v4l2_ctrl *ctrl)
>>   	case V4L2_CTRL_TYPE_U32:
>>   		pr_cont("%u", (unsigned)*ptr.p_u32);
>>   		break;
>> +	case V4L2_CTRL_TYPE_S8:
>> +		pr_cont("%d", *ptr.p_s8);
>> +		break;
>>   	case V4L2_CTRL_TYPE_AREA:
>>   		pr_cont("%ux%u", ptr.p_area->width, ptr.p_area->height);
>>   		break;
>> @@ -1442,6 +1448,8 @@ static int std_validate_elem(const struct v4l2_ctrl *ctrl, u32 idx,
>>   		return ROUND_TO_RANGE(ptr.p_u16[idx], u16, ctrl);
>>   	case V4L2_CTRL_TYPE_U32:
>>   		return ROUND_TO_RANGE(ptr.p_u32[idx], u32, ctrl);
>> +	case V4L2_CTRL_TYPE_S8:
>> +		return ROUND_TO_RANGE(ptr.p_s8[idx], u8, ctrl);
>>   
>>   	case V4L2_CTRL_TYPE_BOOLEAN:
>>   		ptr.p_s32[idx] = !!ptr.p_s32[idx];
>> @@ -2037,6 +2045,9 @@ static struct v4l2_ctrl *v4l2_ctrl_new(struct v4l2_ctrl_handler *hdl,
>>   	case V4L2_CTRL_TYPE_U32:
>>   		elem_size = sizeof(u32);
>>   		break;
>> +	case V4L2_CTRL_TYPE_S8:
>> +		elem_size = sizeof(s8);
>> +		break;
>>   	case V4L2_CTRL_TYPE_MPEG2_SEQUENCE:
>>   		elem_size = sizeof(struct v4l2_ctrl_mpeg2_sequence);
>>   		break;
>> diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
>> index 327976b14d50b73a631e4d2ed95d9f4d146c45ab..9a68a3555e349f1e55aa01af5c10f08201d62bae 100644
>> --- a/include/media/v4l2-ctrls.h
>> +++ b/include/media/v4l2-ctrls.h
>> @@ -27,6 +27,7 @@ struct video_device;
>>   
>>   /**
>>    * union v4l2_ctrl_ptr - A pointer to a control value.
>> + * @p_s8:			Pointer to a 8-bit signed value.
>>    * @p_s32:			Pointer to a 32-bit signed value.
>>    * @p_s64:			Pointer to a 64-bit signed value.
>>    * @p_u8:			Pointer to a 8-bit unsigned value.
>> @@ -61,6 +62,7 @@ struct video_device;
>>    * @p_const:			Pointer to a constant compound value.
>>    */
>>   union v4l2_ctrl_ptr {
>> +	s8 *p_s8;
>>   	s32 *p_s32;
>>   	s64 *p_s64;
>>   	u8 *p_u8;
>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>> index 5373dba640fae3d19247ab1c74ba336e05dc0fe0..ac588d0093df9cc35c11d0b9d41d052d5e800925 100644
>> --- a/include/uapi/linux/videodev2.h
>> +++ b/include/uapi/linux/videodev2.h
>> @@ -1884,6 +1884,7 @@ struct v4l2_ext_control {
>>   		__s64 value64;
>>   		char __user *string;
>>   		__u8 __user *p_u8;
>> +		__s8 __user *p_s8;
>>   		__u16 __user *p_u16;
>>   		__u32 __user *p_u32;
>>   		__s32 __user *p_s32;
>> @@ -1961,6 +1962,7 @@ enum v4l2_ctrl_type {
>>   	V4L2_CTRL_TYPE_U8	     = 0x0100,
>>   	V4L2_CTRL_TYPE_U16	     = 0x0101,
>>   	V4L2_CTRL_TYPE_U32	     = 0x0102,
>> +	V4L2_CTRL_TYPE_S8	     = 0x0103,
>>   	V4L2_CTRL_TYPE_AREA          = 0x0106,
>>   	V4L2_CTRL_TYPE_RECT	     = 0x0107,
>>   
>>