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-rw-r--r--include/linux/usb.h6
1 files changed, 5 insertions, 1 deletions
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 41d1a644c9d4..2d1ac5058534 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -796,6 +796,10 @@ typedef void (*usb_complete_t)(struct urb *, struct pt_regs *);
* of the iso_frame_desc array, and the number of errors is reported in
* error_count. Completion callbacks for ISO transfers will normally
* (re)submit URBs to ensure a constant transfer rate.
+ *
+ * Note that even fields marked "public" should not be touched by the driver
+ * when the urb is owned by the hcd, that is, since the call to
+ * usb_submit_urb() till the entry into the completion routine.
*/
struct urb
{
@@ -803,12 +807,12 @@ struct urb
struct kref kref; /* reference count of the URB */
spinlock_t lock; /* lock for the URB */
void *hcpriv; /* private data for host controller */
- struct list_head urb_list; /* list pointer to all active urbs */
int bandwidth; /* bandwidth for INT/ISO request */
atomic_t use_count; /* concurrent submissions counter */
u8 reject; /* submissions will fail */
/* public, documented fields in the urb that can be used by drivers */
+ struct list_head urb_list; /* list head for use by the urb owner */
struct usb_device *dev; /* (in) pointer to associated device */
unsigned int pipe; /* (in) pipe information */
int status; /* (return) non-ISO status */
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