Re: [PATCH v2] usb: gadget: uvc: Add H264 frame format support

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Jul 11, 2024 at 01:53:04PM +0530, Akash Kumar wrote:
> Add support for framebased frame format which can be used to support
> multiple formats like H264 or H265 other than mjpeg and YUV frames.
> 
> Framebased format is set to H264 by default, which can be updated to
> other formats by updating the GUID through guid configfs attribute.
> Using Different structures for all 3 formats as H264 has different
> structure than mjpeg and uncompressed which will be paased to
> frame make func based on active format instead of common frame
> structure, have updated all apis in driver accordingly.
> h264 is not recognized by hosts machine during enumeration
> with common frame structure, so we need to pass h264 frame
> structure separately.
> 
> Signed-off-by: Akash Kumar <quic_akakum@quicinc.com>
> ---
>  .../ABI/testing/configfs-usb-gadget-uvc       |  88 ++-
>  drivers/usb/gadget/function/uvc_configfs.c    | 570 +++++++++++++++---
>  drivers/usb/gadget/function/uvc_configfs.h    |  34 +-
>  drivers/usb/gadget/function/uvc_v4l2.c        |  80 ++-
>  include/uapi/linux/usb/video.h                |  62 ++
>  5 files changed, 714 insertions(+), 120 deletions(-)
> 
> Changes for v2:
> - Added H264 frame format Details in Documentation/ABI/
>   and new configsfs attribute path for mjpeg and
>   uncompresseed formats.
> 
> diff --git a/Documentation/ABI/testing/configfs-usb-gadget-uvc b/Documentation/ABI/testing/configfs-usb-gadget-uvc
> index 4feb692c4c1d..2580083cdcc5 100644
> --- a/Documentation/ABI/testing/configfs-usb-gadget-uvc
> +++ b/Documentation/ABI/testing/configfs-usb-gadget-uvc
> @@ -224,13 +224,13 @@ Description:	Additional color matching descriptors
>  					  white
>  		========================  ======================================
>  
> -What:		/config/usb-gadget/gadget/functions/uvc.name/streaming/mjpeg
> -Date:		Dec 2014
> +What:		/config/usb-gadget/gadget/functions/uvc.name/streaming/mjpeg/name

You are changing an existing api, how will all existing code handle
this?  Will it not break?  What is ensuring that this will work as-is
ok?

> -#define UVCG_FRAME_ATTR(cname, aname, bits) \
> -static ssize_t uvcg_frame_##cname##_show(struct config_item *item, char *page)\
> +#define UVCG_FRAME_ATTR(cname, fname, bits) \
> +static ssize_t uvcg_frame_##fname##_##cname##_show(struct config_item *item, char *page)\
>  {									\
>  	struct uvcg_frame *f = to_uvcg_frame(item);			\
>  	struct f_uvc_opts *opts;					\
> @@ -1936,14 +1941,14 @@ static ssize_t uvcg_frame_##cname##_show(struct config_item *item, char *page)\
>  	opts = to_f_uvc_opts(opts_item);				\
>  									\
>  	mutex_lock(&opts->lock);					\
> -	result = sprintf(page, "%u\n", f->frame.cname);			\
> +	result = scnprintf(page, PAGE_SIZE, "%u\n", f->frame.fname.cname);\

sysfs_emit() is made for this.

thanks,

greg k-h