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

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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: Felipe Balbi <felipe.balbi@linux.intel.com>
This commit is contained in:
Felipe Balbi 2016-09-26 10:51:18 +03:00
parent a909d3e636
commit 541b6fe630
1 changed files with 19 additions and 0 deletions
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19
include/uapi/linux/usb/ch9.h
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@ -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)
{