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

[Takashi Iwai]

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.

Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 drivers/usb/core/urb.c | 28 +++++++++++++++++++++++++---
 include/linux/usb.h    |  2 ++
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
index 47903d510955..580dfaec8af7 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
+};
+
+/**
+ * usb_urb_ep_check_type - 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_check_type(const struct urb *urb)
+{
+	const struct usb_host_endpoint *ep;
+
+	ep = usb_pipe_endpoint(urb->dev, urb->pipe);
+	if (!ep)
+		return -EINVAL;
+	if (usb_pipetype(urb->pipe) != pipetypes[usb_endpoint_type(&ep->desc)])
+		return -EINVAL;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_urb_ep_check_type);
+
 /**
  * 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;
diff --git a/include/linux/usb.h b/include/linux/usb.h
index cb9fbd54386e..2b861804fffa 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -1728,6 +1728,8 @@ static inline int usb_urb_dir_out(struct urb *urb)
 	return (urb->transfer_flags & URB_DIR_MASK) == URB_DIR_OUT;
 }
 
+int usb_urb_ep_type_check(const struct urb *urb);
+
 void *usb_alloc_coherent(struct usb_device *dev, size_t size,
 	gfp_t mem_flags, dma_addr_t *dma);
 void usb_free_coherent(struct usb_device *dev, size_t size,
-- 
2.14.2