Re: [RFCv1 PATCH 1/3] V4L2: Add per-device-node capabilities

[Sylwester Nawrocki <snjw23@gmail.com>]

Hello Hans,

On 11/07/2011 11:37 AM, Hans Verkuil wrote:
> From: Hans Verkuil<hans.verkuil@cisco.com>
> 
> If V4L2_CAP_DEVICE_CAPS is set, then the new device_caps field is filled with
> the capabilities of the opened device node.
> 
> The capabilities field traditionally contains the capabilities of the whole
> device. E.g., if you open video0, then if it contains VBI caps then that means
> that there is a corresponding vbi node as well. And the capabilities field of
> both the video and vbi node should contain identical caps.
> 
> However, it would be very useful to also have a capabilities field that contains
> just the caps for the currently open device, hence the new CAP bit and field.
> 
> Signed-off-by: Hans Verkuil<hans.verkuil@cisco.com>
> ---
>   include/linux/videodev2.h |    7 +++++--
>   1 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
> index 4b752d5..2b6338b 100644
> --- a/include/linux/videodev2.h
> +++ b/include/linux/videodev2.h
> @@ -243,8 +243,9 @@ struct v4l2_capability {
>   	__u8	card[32];	/* i.e. "Hauppauge WinTV" */
>   	__u8	bus_info[32];	/* "PCI:" + pci_name(pci_dev) */
>   	__u32   version;        /* should use KERNEL_VERSION() */
> -	__u32	capabilities;	/* Device capabilities */
> -	__u32	reserved[4];
> +	__u32	capabilities;	/* Global device capabilities */
> +	__u32	device_caps;	/* Device node capabilities */

How about changing this to

	__u32	devnode_caps;	/* Device node capabilities */

> +	__u32	reserved[3];
>   };
> 
>   /* Values for 'capabilities' field */
> @@ -274,6 +275,8 @@ struct v4l2_capability {
>   #define V4L2_CAP_ASYNCIO                0x02000000  /* async I/O */
>   #define V4L2_CAP_STREAMING              0x04000000  /* streaming I/O ioctls */
> 
> +#define V4L2_CAP_DEVICE_CAPS            0x80000000  /* sets device capabilities field */

..and

#define V4L2_CAP_DEVNODE_CAPS            0x80000000  /* sets device node capabilities field */

?

'device' might suggest a whole physical device/system at first sight.
Maybe devnode_caps is not be the best name but it seems more explicit and
less confusing :) 

It's just my personal opinion though.

--
Regards,
Sylwester