[alsa-devel] [PATCH v2 1/9] usb: core: Add a helper function to check the validity of EP type in URB

[Johan Hovold]

On Wed, Oct 11, 2017 at 12:36:38PM +0200, Takashi Iwai wrote:
> This patch adds a new helper function to perform a sanity check of the
> given URB to see whether it contains a valid endpoint.  It's a light-
> weight version of what usb_submit_urb() does, but without the kernel
> warning followed by the stack trace, just returns an error code.
> 
> Especially for a driver that doesn't parse the descriptor but fills
> the URB with the fixed endpoint (e.g. some quirks for non-compliant
> devices), this kind of check is preferable at the probe phase before
> actually submitting the urb.
> 
> Tested-by: Andrey Konovalov <andreyknvl at google.com>
> Signed-off-by: Takashi Iwai <tiwai at suse.de>
> ---
> v1->v2:
> * Fix function name typos
> * Call usb_urb_ep_type_check() in usb_submit_urb(), too
> 
>  drivers/usb/core/urb.c | 30 ++++++++++++++++++++++++++----
>  include/linux/usb.h    |  2 ++
>  2 files changed, 28 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
> index 47903d510955..8b800e34407b 100644
> --- a/drivers/usb/core/urb.c
> +++ b/drivers/usb/core/urb.c
> @@ -187,6 +187,31 @@ EXPORT_SYMBOL_GPL(usb_unanchor_urb);
>  
>  /*-------------------------------------------------------------------*/
>  
> +static const int pipetypes[4] = {
> +	PIPE_CONTROL, PIPE_ISOCHRONOUS, PIPE_BULK, PIPE_INTERRUPT
> +};

No this one is no longer used outside of usb_urb_ep_type_check().

> +
> +/**
> + * usb_urb_ep_type_check - sanity check of endpoint in the given urb
> + * @urb: urb to be checked
> + *
> + * This performs a light-weight sanity check for the endpoint in the
> + * given urb.  It returns 0 if the urb contains a valid endpoint, otherwise
> + * a negative error code.
> + */
> +int usb_urb_ep_type_check(const struct urb *urb)
> +{
> +	const struct usb_host_endpoint *ep;
> +
> +	ep = usb_pipe_endpoint(urb->dev, urb->pipe);
> +	if (!ep)
> +		return -EINVAL;

And I know Greg asked you to call this function from usb_submit_urb()
which have already done the above ep-lookup once. Maybe not that many
extra cycles, but still seems unnecessary to me.

> +	if (usb_pipetype(urb->pipe) != pipetypes[usb_endpoint_type(&ep->desc)])
> +		return -EINVAL;
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(usb_urb_ep_type_check);
> +
>  /**
>   * usb_submit_urb - issue an asynchronous transfer request for an endpoint
>   * @urb: pointer to the urb describing the request
> @@ -326,9 +351,6 @@ EXPORT_SYMBOL_GPL(usb_unanchor_urb);
>   */
>  int usb_submit_urb(struct urb *urb, gfp_t mem_flags)
>  {
> -	static int			pipetypes[4] = {
> -		PIPE_CONTROL, PIPE_ISOCHRONOUS, PIPE_BULK, PIPE_INTERRUPT
> -	};
>  	int				xfertype, max;
>  	struct usb_device		*dev;
>  	struct usb_host_endpoint	*ep;
> @@ -444,7 +466,7 @@ int usb_submit_urb(struct urb *urb, gfp_t mem_flags)
>  	 */
>  
>  	/* Check that the pipe's type matches the endpoint's type */
> -	if (usb_pipetype(urb->pipe) != pipetypes[xfertype])
> +	if (usb_urb_ep_type_check(urb))
>  		dev_WARN(&dev->dev, "BOGUS urb xfer, pipe %x != type %x\n",
>  			usb_pipetype(urb->pipe), pipetypes[xfertype]);

Johan