Re: [PATCH 2/6] usb: gadget: uvc: Add struct for color matching in configs

[Kieran Bingham <kieran.bingham@ideasonboard.com>]

Quoting Daniel Scally (2022-12-13 08:37:32)
> Color matching descriptors are meant to be a per-format piece of data
> and we need to be able to support different descriptors for different
> formats. As a preliminary step towards that goal, switch the default
> color matching configfs functionality to point to an instance of a
> new struct uvcg_cmd (for "color matching descriptor"). Use the same

Hrm .. I can't see 'cmd' and not think 'command' ... but longer names
are longer ...



> default values for its attributes as the currently hard-coded ones so
> that the interface to userspace is consistent.
> 
> Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
> ---
>  drivers/usb/gadget/function/uvc_configfs.c | 55 ++++++++++++++++------
>  drivers/usb/gadget/function/uvc_configfs.h |  8 ++++
>  2 files changed, 49 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/usb/gadget/function/uvc_configfs.c b/drivers/usb/gadget/function/uvc_configfs.c
> index 26d092790f12..9918e7b6a023 100644
> --- a/drivers/usb/gadget/function/uvc_configfs.c
> +++ b/drivers/usb/gadget/function/uvc_configfs.c
> @@ -1788,20 +1788,19 @@ static ssize_t uvcg_color_matching_##cname##_show(                      \
>         struct config_item *item, char *page)                           \
>  {                                                                      \
>         struct config_group *group = to_config_group(item);             \
> +       struct uvcg_cmd *cmd = to_uvcg_cmd(group);                      \
>         struct f_uvc_opts *opts;                                        \
>         struct config_item *opts_item;                                  \
>         struct mutex *su_mutex = &group->cg_subsys->su_mutex;           \
> -       struct uvc_color_matching_descriptor *cd;                       \
>         int result;                                                     \
>                                                                         \
>         mutex_lock(su_mutex); /* for navigating configfs hierarchy */   \
>                                                                         \
>         opts_item = group->cg_item.ci_parent->ci_parent->ci_parent;     \
>         opts = to_f_uvc_opts(opts_item);                                \
> -       cd = &opts->uvc_color_matching;                                 \
>                                                                         \
>         mutex_lock(&opts->lock);                                        \
> -       result = sprintf(page, "%u\n", le##bits##_to_cpu(cd->aname));   \
> +       result = sprintf(page, "%u\n", le##bits##_to_cpu(cmd->desc.aname));\
>         mutex_unlock(&opts->lock);                                      \
>                                                                         \
>         mutex_unlock(su_mutex);                                         \
> @@ -1823,29 +1822,57 @@ static struct configfs_attribute *uvcg_color_matching_attrs[] = {
>         NULL,
>  };
>  
> -static const struct uvcg_config_group_type uvcg_color_matching_type = {
> -       .type = {
> -               .ct_item_ops    = &uvcg_config_item_ops,
> -               .ct_attrs       = uvcg_color_matching_attrs,
> -               .ct_owner       = THIS_MODULE,
> -       },
> -       .name = "default",
> +static void uvcg_color_matching_release(struct config_item *item)
> +{
> +       struct uvcg_cmd *cmd;
> +
> +       cmd = to_uvcg_cmd(to_config_group(item));
> +       kfree(cmd);
> +}
> +
> +static struct configfs_item_operations uvcg_color_matching_item_ops = {
> +       .release        = uvcg_color_matching_release,
> +};
> +
> +static const struct config_item_type uvcg_color_matching_type = {
> +       .ct_item_ops    = &uvcg_color_matching_item_ops,
> +       .ct_attrs       = uvcg_color_matching_attrs,
> +       .ct_owner       = THIS_MODULE,
>  };
>  
>  /* -----------------------------------------------------------------------------
>   * streaming/color_matching
>   */
>  
> +static int uvcg_color_matching_create_children(struct config_group *parent)
> +{
> +       struct uvcg_cmd *cmd;
> +
> +       cmd = kzalloc(sizeof(*cmd), GFP_KERNEL);
> +       if (!cmd)
> +               return -ENOMEM;
> +
> +       cmd->desc.bLength = UVC_DT_COLOR_MATCHING_SIZE;
> +       cmd->desc.bDescriptorType = USB_DT_CS_INTERFACE;
> +       cmd->desc.bDescriptorSubType = UVC_VS_COLORFORMAT;
> +       cmd->desc.bColorPrimaries = 1;
> +       cmd->desc.bTransferCharacteristics = 1;
> +       cmd->desc.bMatrixCoefficients = 4;

I realise these values were taken directly as existing code, but
particularly in regards to how these values will be set from userspace -
is it easy enough to have some common definitions in a preceeding patch
that state the supported values here from the spec, to avoid 'magic
values' here ...

A header with defines or an enum isn't going to be usable from a bash
script configuring configfs, but at least a compiled program could use
the definitions.


> +
> +       config_group_init_type_name(&cmd->group, "default",
> +                                   &uvcg_color_matching_type);
> +       configfs_add_default_group(&cmd->group, parent);
> +
> +       return 0;
> +}
> +
>  static const struct uvcg_config_group_type uvcg_color_matching_grp_type = {
>         .type = {
>                 .ct_item_ops    = &uvcg_config_item_ops,
>                 .ct_owner       = THIS_MODULE,
>         },
>         .name = "color_matching",
> -       .children = (const struct uvcg_config_group_type*[]) {
> -               &uvcg_color_matching_type,
> -               NULL,
> -       },
> +       .create_children = uvcg_color_matching_create_children,
>  };
>  
>  /* -----------------------------------------------------------------------------
> diff --git a/drivers/usb/gadget/function/uvc_configfs.h b/drivers/usb/gadget/function/uvc_configfs.h
> index ad2ec8c4c78c..f990739838d5 100644
> --- a/drivers/usb/gadget/function/uvc_configfs.h
> +++ b/drivers/usb/gadget/function/uvc_configfs.h
> @@ -37,6 +37,14 @@ static inline struct uvcg_control_header *to_uvcg_control_header(struct config_i
>         return container_of(item, struct uvcg_control_header, item);
>  }
>  
> +struct uvcg_cmd {
> +       struct config_group group;
> +       struct uvc_color_matching_descriptor desc;
> +};
> +
> +#define to_uvcg_cmd(group_ptr) \
> +container_of(group_ptr, struct uvcg_cmd, group)
> +
>  enum uvcg_format_type {
>         UVCG_UNCOMPRESSED = 0,
>         UVCG_MJPEG,
> -- 
> 2.34.1
>