[PATCH] USB: update urb documentation

[linux-2.6-omap-h63xx.git] / include / linux / usb.h

diff --git a/include/linux/usb.h b/include/linux/usb.h
index 41d1a644c9d43aa8206cf2b6e708c4a8173b7fd2..2d1ac5058534cdd8db3ecb86233ab31d247e2c44 100644 (file)
--- 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 */