Re: [PATCH] uvcvideo: Apply flags from device to actual properties

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Hi Edgar,

On 18/08/17 11:12, Edgar Thier wrote:
> 
> Use flags the device exposes for UVC controls.
> This allows the device to define which property flags are set.
> 
> Since some cameras offer auto-adjustments for properties (e.g. auto-gain),
> the values of other properties (e.g. gain) can change in the camera.
> Examining the flags ensures that the driver is aware of such properties.
> 
> Signed-off-by: Edgar Thier <info@xxxxxxxxxxxxxx>> ---
>  drivers/media/usb/uvc/uvc_ctrl.c | 58 +++++++++++++++++++++++++++-------------
>  1 file changed, 40 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index c2ee6e3..6922c0cb 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1629,6 +1629,9 @@ static void uvc_ctrl_fixup_xu_info(struct uvc_device *dev,
>  	}
>  }
> 
> +static int uvc_ctrl_get_flags(struct uvc_device *dev, const struct uvc_control *ctrl,
> +	const struct uvc_control_info *info);

Rather than forward declaring the function ... Could you put the function higher
in the module please?

> +
>  /*
>   * Query control information (size and flags) for XU controls.
>   */
> @@ -1659,24 +1662,7 @@ static int uvc_ctrl_fill_xu_info(struct uvc_device *dev,
> 
>  	info->size = le16_to_cpup((__le16 *)data);
> 
> -	/* Query the control information (GET_INFO) */
> -	ret = uvc_query_ctrl(dev, UVC_GET_INFO, ctrl->entity->id, dev->intfnum,
> -			     info->selector, data, 1);
> -	if (ret < 0) {
> -		uvc_trace(UVC_TRACE_CONTROL,
> -			  "GET_INFO failed on control %pUl/%u (%d).\n",
> -			  info->entity, info->selector, ret);
> -		goto done;
> -	}
> -
> -	info->flags = UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX
> -		    | UVC_CTRL_FLAG_GET_RES | UVC_CTRL_FLAG_GET_DEF
> -		    | (data[0] & UVC_CONTROL_CAP_GET ?
> -		       UVC_CTRL_FLAG_GET_CUR : 0)
> -		    | (data[0] & UVC_CONTROL_CAP_SET ?
> -		       UVC_CTRL_FLAG_SET_CUR : 0)
> -		    | (data[0] & UVC_CONTROL_CAP_AUTOUPDATE ?
> -		       UVC_CTRL_FLAG_AUTO_UPDATE : 0);
> +	info->flags = uvc_ctrl_get_flags(dev, ctrl, info);
> 
>  	uvc_ctrl_fixup_xu_info(dev, ctrl, info);
> 
> @@ -1884,6 +1870,40 @@ int uvc_ctrl_restore_values(struct uvc_device *dev)
>   */
> 
>  /*
> + * Retrieve flags for a given control
> + */
> +static int uvc_ctrl_get_flags(struct uvc_device *dev, const struct uvc_control *ctrl,
> +	const struct uvc_control_info *info)
> +{
> +	u8 *data;
> +	int ret = 0;
> +	int flags = 0;
> +
> +	data = kmalloc(2, GFP_KERNEL);

kmalloc seems a bit of an overhead for 2 bytes (only one of which is used).
Can this use local stack storage?

(Laurent, looks like you originally wrote the code that did that, was there a
reason for the kmalloc for 2 bytes?)

> +	if (data == NULL)
> +		return -ENOMEM;

This will set the callers 'flags' to -ENOMEM ? Is that desired?

Of course removing the kmalloc will fix that anyway ...


> +
> +	ret = uvc_query_ctrl(dev, UVC_GET_INFO, ctrl->entity->id, dev->intfnum,
> +						 info->selector, data, 1);
> +	if (ret < 0) {
> +		uvc_trace(UVC_TRACE_CONTROL,
> +				  "GET_INFO failed on control %pUl/%u (%d).\n",
> +				  info->entity, info->selector, ret);
> +	} else {
> +		flags = UVC_CTRL_FLAG_GET_MIN | UVC_CTRL_FLAG_GET_MAX
> +			| UVC_CTRL_FLAG_GET_RES | UVC_CTRL_FLAG_GET_DEF
> +			| (data[0] & UVC_CONTROL_CAP_GET ?
> +			   UVC_CTRL_FLAG_GET_CUR : 0)
> +			| (data[0] & UVC_CONTROL_CAP_SET ?
> +			   UVC_CTRL_FLAG_SET_CUR : 0)
> +			| (data[0] & UVC_CONTROL_CAP_AUTOUPDATE ?
> +			   UVC_CTRL_FLAG_AUTO_UPDATE : 0);
> +	}
> +	kfree(data);
> +	return flags;
> +}
> +
> +/*
>   * Add control information to a given control.
>   */
>  static int uvc_ctrl_add_info(struct uvc_device *dev, struct uvc_control *ctrl,
> @@ -1902,6 +1922,8 @@ static int uvc_ctrl_add_info(struct uvc_device *dev, struct uvc_control *ctrl,
>  		goto done;
>  	}
> 
> +	ctrl->info.flags = uvc_ctrl_get_flags(dev, ctrl, info);
> +
>  	ctrl->initialized = 1;
> 
>  	uvc_trace(UVC_TRACE_CONTROL, "Added control %pUl/%u to device %s "
> 



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