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

[Takashi Iwai]

On Wed, 11 Oct 2017 16:14:55 +0200,
Johan Hovold wrote:
> 
> 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().

It is used in the error message, so I kept it here.


> > +
> > +/**
> > + * 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.

Yeah, we can do micro-optimization later if needed, e.g. splitting the
function.  It's a question of balance between code optimization and
readability...


thanks,

Takashi

> > +	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
>