Re: [PATCH v7 3/7] media: uvcvideo: Add support for compound controls

Laurent Pinchart
2022-08-24T19:57:01Z

Hi Yunke,

Thank you for the patch.

On Tue, Jun 28, 2022 at 04:57:01PM +0900, Yunke Cao wrote:
> Supports getting/setting current value.
> Supports getting default value.
> Handles V4L2_CTRL_FLAG_NEXT_COMPOUND.
>
> Signed-off-by: Yunke Cao <yunkec@google.com>
> ---
> drivers/media/usb/uvc/uvc_ctrl.c | 279 ++++++++++++++++++++++++++-----
> drivers/media/usb/uvc/uvcvideo.h | 4 +
> 2 files changed, 238 insertions(+), 45 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index 772d9d28a520..508ee04afbcd 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -815,6 +815,34 @@ static void uvc_set_le_value(struct uvc_control_mapping *mapping,
> }
> }
>
> +/* Extract the byte array specified by mapping->offset and mapping->size
> + * stored at 'data' to the output array 'data_out'.
> + */

Please use the

/*
* multi
* line
*/

style instead of

/* multi
* line
*/

The uvcvideo driver has recently switched to the former in commit
699b9a86a3f0 ("media: uvcvideo: Fix comment blocks style").

> +static int uvc_get_array(struct uvc_control_mapping *mapping, const u8 *data,
> + u8 *data_out)
> +{
> + // Only supports byte-aligned data.

And no C++-style comments either please.

> + if (WARN_ON(mapping->offset % 8 || mapping->size % 8))
> + return -EINVAL;
> +
> + memcpy(data_out, data + mapping->offset / 8, mapping->size / 8);
> + return 0;
> +}
> +
> +/* Copy the byte array 'data_in' to the destination specified by mapping->offset
> + * and mapping->size stored at 'data'.
> + */
> +static int uvc_set_array(struct uvc_control_mapping *mapping, const u8 *data_in,
> + u8 *data)
> +{
> + // Only supports byte-aligned data.
> + if (WARN_ON(mapping->offset % 8 || mapping->size % 8))
> + return -EINVAL;
> +
> + memcpy(data + mapping->offset / 8, data_in, mapping->size / 8);
> + return 0;
> +}
> +

Could you add here a

static bool
uvc_ctrl_mapping_is_compound(const struct uvc_control_mapping *mapping)
{
return mapping->v4l2_type >= V4L2_CTRL_COMPOUND_TYPES;
}

and use it below ? That would be clearer I think.

> /* ------------------------------------------------------------------------
> * Terminal and unit management
> */
> @@ -831,7 +859,7 @@ static int uvc_entity_match_guid(const struct uvc_entity *entity,
>
> static void __uvc_find_control(struct uvc_entity *entity, u32 v4l2_id,
> struct uvc_control_mapping **mapping, struct uvc_control **control,
> - int next)
> + int next, int next_compound)
> {
> struct uvc_control *ctrl;
> struct uvc_control_mapping *map;
> @@ -846,14 +874,18 @@ static void __uvc_find_control(struct uvc_entity *entity, u32 v4l2_id,
> continue;
>
> list_for_each_entry(map, &ctrl->info.mappings, list) {
> - if ((map->id == v4l2_id) && !next) {
> + if (map->id == v4l2_id && !next && !next_compound) {
> *control = ctrl;
> *mapping = map;
> return;
> }
>
> if ((*mapping == NULL || (*mapping)->id > map->id) &&
> - (map->id > v4l2_id) && next) {
> + (map->id > v4l2_id) &&
> + ((map->v4l2_type < V4L2_CTRL_COMPOUND_TYPES &&
> + next) ||
> + (map->v4l2_type >= V4L2_CTRL_COMPOUND_TYPES &&
> + next_compound))) {
> *control = ctrl;
> *mapping = map;
> }

This could become for instance

if ((*mapping == NULL || (*mapping)->id > map->id) &&
(map->id > v4l2_id) &&
((!uvc_ctrl_mapping_is_compound(map) && next) ||
(uvc_ctrl_mapping_is_compound(map) && next_compound))) {
*control = ctrl;
*mapping = map;
}

> @@ -867,6 +899,7 @@ static struct uvc_control *uvc_find_control(struct uvc_video_chain *chain,
> struct uvc_control *ctrl = NULL;
> struct uvc_entity *entity;
> int next = v4l2_id & V4L2_CTRL_FLAG_NEXT_CTRL;
> + int next_compound = v4l2_id & V4L2_CTRL_FLAG_NEXT_COMPOUND;
>
> *mapping = NULL;
>
> @@ -875,12 +908,13 @@ static struct uvc_control *uvc_find_control(struct uvc_video_chain *chain,
>
> /* Find the control. */
> list_for_each_entry(entity, &chain->entities, chain) {
> - __uvc_find_control(entity, v4l2_id, mapping, &ctrl, next);
> - if (ctrl && !next)
> + __uvc_find_control(entity, v4l2_id, mapping, &ctrl, next,
> + next_compound);
> + if (ctrl && !next && !next_compound)
> return ctrl;
> }
>
> - if (ctrl == NULL && !next)
> + if (!ctrl && !next && !next_compound)
> uvc_dbg(chain->dev, CONTROL, "Control 0x%08x not found\n",
> v4l2_id);
>
> @@ -943,6 +977,39 @@ static int uvc_ctrl_populate_cache(struct uvc_video_chain *chain,
> return 0;
> }
>
> +static int __uvc_ctrl_load_cur(struct uvc_video_chain *chain,
> + struct uvc_control *ctrl)
> +{

I would declare

u8 data;

here, and

> + int ret = 0;
> +
> + if ((ctrl->info.flags & UVC_CTRL_FLAG_GET_CUR) == 0)
> + return -EACCES;
> +
> + if (ctrl->loaded)
> + return 0;
> +

set

data = uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT);

here, and

> + if (ctrl->entity->get_cur) {
> + ret = ctrl->entity->get_cur(chain->dev,
> + ctrl->entity,
> + ctrl->info.selector,
> + uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT),
> + ctrl->info.size);

improve indentation here

ret = ctrl->entity->get_cur(chain->dev, ctrl->entity,
ctrl->info.selector, data,
ctrl->info.size);

> + } else {

and also use data here

> + ret = uvc_query_ctrl(chain->dev, UVC_GET_CUR,
> + ctrl->entity->id, chain->dev->intfnum,
> + ctrl->info.selector,
> + uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT),
> + ctrl->info.size);

ret = uvc_query_ctrl(chain->dev, UVC_GET_CUR,
ctrl->entity->id, chain->dev->intfnum,
ctrl->info.selector, data,
ctrl->info.size);

> + }
> +
> + if (ret < 0)
> + return ret;
> +
> + ctrl->loaded = 1;
> +
> + return ret;
> +}
> +
> static s32 __uvc_ctrl_get_value(struct uvc_control_mapping *mapping,
> const u8 *data)
> {
> @@ -963,35 +1030,19 @@ static s32 __uvc_ctrl_get_value(struct uvc_control_mapping *mapping,
> return value;
> }
>
> -static int __uvc_ctrl_get(struct uvc_video_chain *chain,
> - struct uvc_control *ctrl, struct uvc_control_mapping *mapping,
> - s32 *value)
> +static int __uvc_ctrl_get_std(struct uvc_video_chain *chain,
> + struct uvc_control *ctrl,
> + struct uvc_control_mapping *mapping,
> + s32 *value)
> {
> int ret;
>
> - if ((ctrl->info.flags & UVC_CTRL_FLAG_GET_CUR) == 0)
> - return -EACCES;
> -
> - if (!ctrl->loaded) {
> - if (ctrl->entity->get_cur) {
> - ret = ctrl->entity->get_cur(chain->dev,
> - ctrl->entity,
> - ctrl->info.selector,
> - uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT),
> - ctrl->info.size);
> - } else {
> - ret = uvc_query_ctrl(chain->dev, UVC_GET_CUR,
> - ctrl->entity->id,
> - chain->dev->intfnum,
> - ctrl->info.selector,
> - uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT),
> - ctrl->info.size);
> - }
> - if (ret < 0)
> - return ret;
> + if (mapping->v4l2_type >= V4L2_CTRL_COMPOUND_TYPES)
> + return -EINVAL;
>
> - ctrl->loaded = 1;
> - }
> + ret = __uvc_ctrl_load_cur(chain, ctrl);
> + if (ret < 0)
> + return ret;
>
> *value = __uvc_ctrl_get_value(mapping,
> uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT));
> @@ -999,6 +1050,57 @@ static int __uvc_ctrl_get(struct uvc_video_chain *chain,
> return 0;
> }
>
> +static int __uvc_ctrl_get_compound_to_user(struct uvc_control_mapping *mapping,

I don't like this name much. One option would be to rename the
__uvc_ctrl_get_compound() function below to
__uvc_ctrl_get_compound_cur() and call this function
__uvc_ctrl_get_compound(). Better options are likely possible.

> + struct uvc_control *ctrl,
> + int id,
> + struct v4l2_ext_control *xctrl)
> +{
> + int ret, size;

size is never negative, make it an unsigned int.

> + u8 *data;
> +
> + if (WARN_ON(!mapping->size % 8))
> + return -EINVAL;

This duplicates a check in the get_array function. Let's move all those
checks to the function that adds mappings.

> +
> + size = mapping->size / 8;
> + if (xctrl->size < size) {
> + xctrl->size = size;
> + return -ENOSPC;
> + }
> +
> + data = kmalloc(size, GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + ret = mapping->get_array(mapping, uvc_ctrl_data(ctrl, id), data);
> + if (ret < 0)
> + goto out;
> +
> + ret = copy_to_user(xctrl->ptr, data, size) ? -EFAULT : 0;
> +
> +out:
> + kfree(data);
> + return ret;
> +}
> +
> +static int __uvc_ctrl_get_compound(struct uvc_video_chain *chain,
> + struct uvc_control *ctrl,
> + struct uvc_control_mapping *mapping,
> + struct v4l2_ext_control *xctrl)
> +{
> + int ret;
> +
> + if (mapping->v4l2_type < V4L2_CTRL_COMPOUND_TYPES)
> + return -EINVAL;
> +
> + ret = __uvc_ctrl_load_cur(chain, ctrl);
> + if (ret < 0)
> + return ret;
> +
> + return __uvc_ctrl_get_compound_to_user(mapping, ctrl,
> + UVC_CTRL_DATA_CURRENT,
> + xctrl);
> +}
> +
> static int __uvc_query_v4l2_class(struct uvc_video_chain *chain, u32 req_id,
> u32 found_id)
> {
> @@ -1102,10 +1204,15 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
>
> if (mapping->master_id)
> __uvc_find_control(ctrl->entity, mapping->master_id,
> - &master_map, &master_ctrl, 0);
> + &master_map, &master_ctrl, 0, 0);
> if (master_ctrl && (master_ctrl->info.flags & UVC_CTRL_FLAG_GET_CUR)) {
> - s32 val;
> - int ret = __uvc_ctrl_get(chain, master_ctrl, master_map, &val);
> + int ret;
> + s32 val = 0;

Move ret after val.

> +
> + if (master_map->v4l2_type >= V4L2_CTRL_COMPOUND_TYPES)
> + return -EINVAL;
> +
> + ret = __uvc_ctrl_get_std(chain, master_ctrl, master_map, &val);
> if (ret < 0)
> return ret;
>
> @@ -1113,6 +1220,15 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
> v4l2_ctrl->flags |= V4L2_CTRL_FLAG_INACTIVE;
> }
>
> + if (v4l2_ctrl->type >= V4L2_CTRL_COMPOUND_TYPES) {
> + v4l2_ctrl->flags |= V4L2_CTRL_FLAG_HAS_PAYLOAD;
> + v4l2_ctrl->default_value = 0;
> + v4l2_ctrl->minimum = 0;
> + v4l2_ctrl->maximum = 0;
> + v4l2_ctrl->step = 0;
> + return 0;
> + }
> +
> if (!ctrl->cached) {
> int ret = uvc_ctrl_populate_cache(chain, ctrl);
> if (ret < 0)
> @@ -1346,11 +1462,12 @@ static void uvc_ctrl_send_slave_event(struct uvc_video_chain *chain,
> u32 changes = V4L2_EVENT_CTRL_CH_FLAGS;
> s32 val = 0;
>
> - __uvc_find_control(master->entity, slave_id, &mapping, &ctrl, 0);
> + __uvc_find_control(master->entity, slave_id, &mapping, &ctrl, 0, 0);
> if (ctrl == NULL)
> return;
>
> - if (__uvc_ctrl_get(chain, ctrl, mapping, &val) == 0)
> + if (mapping->v4l2_type >= V4L2_CTRL_COMPOUND_TYPES ||
> + __uvc_ctrl_get_std(chain, ctrl, mapping, &val) == 0)
> changes |= V4L2_EVENT_CTRL_CH_VALUE;
>
> uvc_ctrl_send_event(chain, handle, ctrl, mapping, val, changes);
> @@ -1517,7 +1634,8 @@ static int uvc_ctrl_add_event(struct v4l2_subscribed_event *sev, unsigned elems)
> u32 changes = V4L2_EVENT_CTRL_CH_FLAGS;
> s32 val = 0;
>
> - if (__uvc_ctrl_get(handle->chain, ctrl, mapping, &val) == 0)
> + if (mapping->v4l2_type >= V4L2_CTRL_COMPOUND_TYPES ||
> + __uvc_ctrl_get_std(handle->chain, ctrl, mapping, &val) == 0)
> changes |= V4L2_EVENT_CTRL_CH_VALUE;
>
> uvc_ctrl_fill_event(handle->chain, &ev, ctrl, mapping, val,
> @@ -1647,7 +1765,7 @@ static int uvc_ctrl_find_ctrl_idx(struct uvc_entity *entity,
>
> for (i = 0; i < ctrls->count; i++) {
> __uvc_find_control(entity, ctrls->controls[i].id, &mapping,
> - &ctrl_found, 0);
> + &ctrl_found, 0, 0);
> if (uvc_control == ctrl_found)
> return i;
> }
> @@ -1694,11 +1812,14 @@ int uvc_ctrl_get(struct uvc_video_chain *chain,
> if (ctrl == NULL)
> return -EINVAL;
>
> - return __uvc_ctrl_get(chain, ctrl, mapping, &xctrl->value);
> + if (mapping->v4l2_type < V4L2_CTRL_COMPOUND_TYPES)
> + return __uvc_ctrl_get_std(chain, ctrl, mapping, &xctrl->value);
> + else
> + return __uvc_ctrl_get_compound(chain, ctrl, mapping, xctrl);
> }
>
> -int uvc_ctrl_get_fixed(struct uvc_video_chain *chain,
> - struct v4l2_ext_control *xctrl)
> +int __uvc_ctrl_get_fixed_std(struct uvc_video_chain *chain,
> + struct v4l2_ext_control *xctrl)
> {
> struct v4l2_queryctrl qc = { .id = xctrl->id };
> int ret = uvc_query_v4l2_ctrl(chain, &qc);
> @@ -1710,6 +1831,56 @@ int uvc_ctrl_get_fixed(struct uvc_video_chain *chain,
> return 0;
> }
>
> +int uvc_ctrl_get_fixed(struct uvc_video_chain *chain,
> + struct v4l2_ext_control *xctrl)
> +{
> + struct uvc_control *ctrl;
> + struct uvc_control_mapping *mapping;
> + int ret;
> +
> + if (__uvc_query_v4l2_class(chain, xctrl->id, 0) >= 0)
> + return -EACCES;
> +

This check comes a bit out of the blue, I think it belongs to another
patch, with a commit message that clearly explain the rationale.

> + ctrl = uvc_find_control(chain, xctrl->id, &mapping);
> + if (!ctrl)
> + return -EINVAL;

And here, you're duplicating the uvc_find_control() call from
uvc_query_v4l2_ctrl(), called in __uvc_ctrl_get_fixed_std().
Furthermore, you're not holding the ctrl_mutex lock here, which I think
is wrong.

I'd like to see a patch before this one that refactors what needs to be
refactored first, and then the introduction of compound types support
without any extra change like this. Splitting code out to
__uvc_ctrl_load_cur() could also be moved to a preparatory patch to
simplify this one, it's quite hard to review.

> +
> + if (mapping->v4l2_type < V4L2_CTRL_COMPOUND_TYPES)
> + return __uvc_ctrl_get_fixed_std(chain, xctrl);
> +
> + if (!ctrl->cached) {
> + ret = uvc_ctrl_populate_cache(chain, ctrl);
> + if (ret < 0)
> + return ret;
> + }
> +
> + return __uvc_ctrl_get_compound_to_user(mapping, ctrl, UVC_CTRL_DATA_DEF,
> + xctrl);
> +}
> +
> +int __uvc_ctrl_set_compound(struct uvc_control_mapping *mapping,
> + struct v4l2_ext_control *xctrl,
> + struct uvc_control *ctrl)
> +{
> + int ret;
> + u8 *data;

Please move ret after data.

> +
> + data = kmalloc(xctrl->size, GFP_KERNEL);

A limit on the size is needed to avoid denial of service attacks.

> + if (!data)
> + return -ENOMEM;
> +
> + ret = copy_from_user(data, xctrl->ptr, xctrl->size);
> + if (ret < 0)
> + goto out;
> +
> + ret = mapping->set_array(mapping, data,
> + uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT));

ret = mapping->set_array(mapping, data,
uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT));

The V4L2 control model is that the kernel can update the value of a
control if the requested value is out of range or otherwise not
acceptable. You should here copy the data back to the user.

> +
> +out:
> + kfree(data);
> + return ret;
> +}
> +
> int uvc_ctrl_set(struct uvc_fh *handle,
> struct v4l2_ext_control *xctrl)
> {
> @@ -1820,8 +1991,14 @@ int uvc_ctrl_set(struct uvc_fh *handle,
> ctrl->info.size);
> }
>
> - mapping->set(mapping, value,
> - uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT));
> + if (mapping->v4l2_type < V4L2_CTRL_COMPOUND_TYPES) {
> + mapping->set(mapping, value,
> + uvc_ctrl_data(ctrl, UVC_CTRL_DATA_CURRENT));
> + } else {
> + ret = __uvc_ctrl_set_compound(mapping, xctrl, ctrl);
> + if (ret < 0)
> + return ret;
> + }
>
> if (ctrl->info.flags & UVC_CTRL_FLAG_ASYNCHRONOUS)
> ctrl->handle = handle;
> @@ -2220,10 +2397,14 @@ static int __uvc_ctrl_add_mapping(struct uvc_video_chain *chain,
> return -ENOMEM;
> }
>
> - if (map->get == NULL)
> + if (!map->get && map->v4l2_type < V4L2_CTRL_COMPOUND_TYPES)
> map->get = uvc_get_le_value;
> - if (map->set == NULL)
> + if (!map->set && map->v4l2_type < V4L2_CTRL_COMPOUND_TYPES)
> map->set = uvc_set_le_value;
> + if (!map->get_array && map->v4l2_type >= V4L2_CTRL_COMPOUND_TYPES)
> + map->get_array = uvc_get_array;
> + if (!map->set_array && map->v4l2_type >= V4L2_CTRL_COMPOUND_TYPES)
> + map->set_array = uvc_set_array;
>
> for (i = 0; i < ARRAY_SIZE(uvc_control_classes); i++) {
> if (V4L2_CTRL_ID2WHICH(uvc_control_classes[i]) ==
> @@ -2233,6 +2414,14 @@ static int __uvc_ctrl_add_mapping(struct uvc_video_chain *chain,
> }
> }
>
> + if (map->v4l2_type < V4L2_CTRL_COMPOUND_TYPES &&
> + WARN_ON(!map->get || !map->set))
> + return -EINVAL;
> +
> + if (map->v4l2_type >= V4L2_CTRL_COMPOUND_TYPES &&
> + WARN_ON(!map->get_array || !map->set_array))
> + return -EINVAL;
> +

Can this happen, given that you set them above if they're null ?

> list_add_tail(&map->list, &ctrl->info.mappings);
> uvc_dbg(chain->dev, CONTROL, "Adding mapping '%s' to control %pUl/%u\n",
> uvc_map_get_name(map), ctrl->info.entity,
> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> index ba028ba7c34e..2f9b75faae83 100644
> --- a/drivers/media/usb/uvc/uvcvideo.h
> +++ b/drivers/media/usb/uvc/uvcvideo.h
> @@ -262,8 +262,12 @@ struct uvc_control_mapping {
>
> s32 (*get)(struct uvc_control_mapping *mapping, u8 query,
> const u8 *data);
> + int (*get_array)(struct uvc_control_mapping *mapping, const u8 *data,
> + u8 *data_out);
> void (*set)(struct uvc_control_mapping *mapping, s32 value,
> u8 *data);
> + int (*set_array)(struct uvc_control_mapping *mapping, const u8 *data_in,
> + u8 *data);

Wouldn't those operations be better names get_compound and set_compound ?

> };
>
> struct uvc_control {

--
Regards,

Laurent Pinchart