Patch "usb: add helper to extract bits 12:11 of wMaxPacketSize" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

usb: add helper to extract bits 12:11 of wMaxPacketSize

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
usb-add-helper-to-extract-bits-12-11-of-wmaxpacketsize.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Felipe Balbi <[email protected]>
Date: Mon, 26 Sep 2016 10:51:18 +0300
Subject: usb: add helper to extract bits 12:11 of wMaxPacketSize

From: Felipe Balbi <[email protected]>

commit 541b6fe63023f3059cf85d47ff2767a3e42a8e44 upstream.

According to USB Specification 2.0 table 9-4, wMaxPacketSize is a bitfield. Endpoint's maxpacket is laid out in bits 10:0. For high-speed, high-bandwidth isochronous endpoints, bits 12:11 contain a multiplier to tell us how many transactions we want to try per uframe.

This means that if we want an isochronous endpoint to issue 3 transfers of 1024 bytes per uframe, wMaxPacketSize should contain the value:

	1024 | (2 << 11)

or 5120 (0x1400). In order to make Host and Peripheral controller drivers' life easier, we're adding a helper which returns bits 12:11. Note that no care is made WRT to checking endpoint type and gadget's speed. That's left for drivers to handle.

---
 include/uapi/linux/usb/ch9.h |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

@@ -423,6 +423,11 @@ struct usb_endpoint_descriptor {
 #define USB_ENDPOINT_XFER_INT		3
 #define USB_ENDPOINT_MAX_ADJUSTABLE	0x80
 
+#define USB_EP_MAXP_MULT_SHIFT	11
+#define USB_EP_MAXP_MULT_MASK	(3 << USB_EP_MAXP_MULT_SHIFT)
+#define USB_EP_MAXP_MULT(m) \
+	(((m) & USB_EP_MAXP_MULT_MASK) >> USB_EP_MAXP_MULT_SHIFT)
+
 /* The USB 3.0 spec redefines bits 5:4 of bmAttributes as interrupt ep type. */
 #define USB_ENDPOINT_INTRTYPE		0x30
 #define USB_ENDPOINT_INTR_PERIODIC	(0 << 4)

@@ -630,6 +635,20 @@ static inline int usb_endpoint_maxp(cons
 	return __le16_to_cpu(epd->wMaxPacketSize);
 }
 
+/**
+ * usb_endpoint_maxp_mult - get endpoint's transactional opportunities
+ * @epd: endpoint to be checked
+ *
+ * Return @epd's wMaxPacketSize[12:11] + 1
+ */
+static inline int
+usb_endpoint_maxp_mult(const struct usb_endpoint_descriptor *epd)
+{
+	int maxp = __le16_to_cpu(epd->wMaxPacketSize);
+
+	return USB_EP_MAXP_MULT(maxp) + 1;
+}
+
 static inline int usb_endpoint_interrupt_type(
 		const struct usb_endpoint_descriptor *epd)
 {

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/usb-add-helper-to-extract-bits-12-11-of-wmaxpacketsize.patch