[PATCH] usbcore doc + minor fixes

Cleaning out my queue of most minor patches:

  - Provides some kerneldoc for 'struct usb_interface' now that
    the API is highlighting it.

  - Fixes usb_set_interface() so it doesn't affect other interfaces.

    This provides the right place for an eventual HCD call to clean
    out now-invalid records of endpoint state, and also gets rid of
    a potential SMP issue where drivers on different interfaces
    calling concurrently could clobber each other.  (Per-interface
    data doesn't need locking except against config changes.)

  - It's OK to pass URB_NO_INTERRUPT hints if you're queueing a
    bunch of interrupt transfers.

The set_interface call should eventually take the interface as a
parameter, it's one of the few left using the "device plus magic
number" identifier.  I have a partial patch for that, but it doesn't
handle the (newish) ALSA usb audio driver or a few other callers.

drivers/usb/core/message.c

@@ -756,6 +756,7 @@ int usb_clear_halt(struct usb_device *dev, int pipe)
  *
  * This is used to enable data transfers on interfaces that may not
  * be enabled by default.  Not all devices support such configurability.
+ * Only the driver bound to an interface may change its setting.
  *
  * Within any given configuration, each interface may have several
  * alternative settings.  These are often used to control levels of
@@ -808,6 +809,22 @@ int usb_set_interface(struct usb_device *dev, int interface, int alternate)
 				   interface, NULL, 0, HZ * 5)) < 0)
 		return ret;
 
+	/* FIXME drivers shouldn't need to replicate/bugfix the logic here
+	 * when they implement async or easily-killable versions of this or
+	 * other "should-be-internal" functions (like clear_halt).
+	 * should hcd+usbcore postprocess control requests?
+	 */
+
+	/* prevent submissions using previous endpoint settings */
+	iface_as = iface->altsetting + iface->act_altsetting;
+	for (i = 0; i < iface_as->bNumEndpoints; i++) {
+		u8	ep = iface_as->endpoint [i].bEndpointAddress;
+		int	out = !(ep & USB_DIR_IN);
+
+		ep &= USB_ENDPOINT_NUMBER_MASK;
+		(out ? dev->epmaxpacketout : dev->epmaxpacketin ) [ep] = 0;
+		// FIXME want hcd hook here, "no such endpoint"
+	}
 	iface->act_altsetting = alternate;
 
 	/* 9.1.1.5: reset toggles for all endpoints affected by this iface-as
@@ -819,21 +836,20 @@ int usb_set_interface(struct usb_device *dev, int interface, int alternate)
 	 * any SetInterface request and hence assume toggles need to be reset.
 	 * However, EP0 toggles are re-synced for every individual transfer
 	 * during the SETUP stage - hence EP0 toggles are "don't care" here.
+	 * (Likewise, EP0 never "halts" on well designed devices.)
 	 */
 
 	iface_as = &iface->altsetting[alternate];
 	for (i = 0; i < iface_as->bNumEndpoints; i++) {
 		u8	ep = iface_as->endpoint[i].bEndpointAddress;
+		int	out = !(ep & USB_DIR_IN);
 
-		usb_settoggle(dev, ep&USB_ENDPOINT_NUMBER_MASK, usb_endpoint_out(ep), 0);
+		ep &= USB_ENDPOINT_NUMBER_MASK;
+		usb_settoggle (dev, ep, out, 0);
+		(out ? dev->epmaxpacketout : dev->epmaxpacketin) [ep]
+			= iface_as->endpoint [ep].wMaxPacketSize;
 	}
 
-	/* usb_set_maxpacket() sets the maxpacket size for all EP in all
-	 * interfaces but it shouldn't do any harm here: we have changed
-	 * the AS for the requested interface only, hence for unaffected
-	 * interfaces it's just re-application of still-valid values.
-	 */
-	usb_set_maxpacket(dev);
 	return 0;
 }
 

drivers/usb/core/urb.c

@@ -272,9 +272,9 @@ int usb_submit_urb(struct urb *urb, int mem_flags)
 	/* enforce simple/standard policy */
 	allowed = USB_ASYNC_UNLINK;	// affects later unlinks
 	allowed |= URB_NO_DMA_MAP;
+	allowed |= URB_NO_INTERRUPT;
 	switch (temp) {
 	case PIPE_BULK:
-		allowed |= URB_NO_INTERRUPT;
 		if (is_out)
 			allowed |= USB_ZERO_PACKET;
 		/* FALLTHROUGH */

include/linux/usb.h

@@ -222,12 +222,42 @@ struct usb_interface_descriptor {
 	int extralen;
 };
 
+/**
+ * struct usb_interface - what usb device drivers talk to
+ * @altsetting: array of interface descriptors, one for each alternate
+ * 	setting that may be selected.  each one includes a set of
+ * 	endpoint configurations.
+ * @num_altsetting: number of altsettings defined.
+ * @act_altsetting: index of current altsetting.  this number is always
+ *	less than num_altsetting.  after the device is configured, each
+ *	interface uses its default setting of zero.
+ * @dev: driver model's view of this device
+ *
+ * USB device drivers attach to interfaces on a physical device.  Each
+ * interface encapsulates a single high level function, such as feeding
+ * an audio stream to a speaker or reporting a change in a volume control.
+ * Many USB devices only have one interface.  The protocol used to talk to
+ * an interface's endpoints can be defined in a usb "class" specification,
+ * or by a product's vendor.  The (default) control endpoint is part of
+ * every interface, but is never listed among the interface's descriptors.
+ *
+ * The driver that is bound to the interface can use standard driver model
+ * calls such as dev_get_drvdata() on the dev member of this structure.
+ *
+ * Each interface may have alternate settings.  The initial configuration
+ * of a device sets the first of these, but the device driver can change
+ * that setting using usb_set_interface().  Alternate settings are often
+ * used to control the the use of periodic endpoints, such as by having
+ * different endpoints use different amounts of reserved USB bandwidth.
+ * All standards-conformant USB devices that use isochronous endpoints
+ * will use them in non-default settings.
+ */
 struct usb_interface {
 	struct usb_interface_descriptor *altsetting;
 
-	int act_altsetting;		/* active alternate setting */
-	int num_altsetting;		/* number of alternate settings */
-	int max_altsetting;		/* total memory allocated */
+	unsigned act_altsetting;	/* active alternate setting */
+	unsigned num_altsetting;	/* number of alternate settings */
+	unsigned max_altsetting;	/* total memory allocated */
 
 	struct usb_driver *driver;	/* driver */
 	struct device dev;		/* interface specific device info */