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Commit 541b6fe6 authored by Felipe Balbi's avatar Felipe Balbi
Browse files

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



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.

Signed-off-by: default avatarFelipe Balbi <felipe.balbi@linux.intel.com>
parent a909d3e6

include/uapi/linux/usb/ch9.h

+19 −0
Original line number Diff line number Diff line
@@ -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(const struct usb_endpoint_descriptor *epd) 
	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)

{