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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: Felipe Balbi <felipe.balbi@linux.intel.com>
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1 changed files with 19 additions and 0 deletions
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@ -423,6 +423,11 @@ struct usb_endpoint_descriptor {
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#define USB_ENDPOINT_XFER_INT 3
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#define USB_ENDPOINT_MAX_ADJUSTABLE 0x80
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#define USB_EP_MAXP_MULT_SHIFT 11
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#define USB_EP_MAXP_MULT_MASK (3 << USB_EP_MAXP_MULT_SHIFT)
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#define USB_EP_MAXP_MULT(m) \
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(((m) & USB_EP_MAXP_MULT_MASK) >> USB_EP_MAXP_MULT_SHIFT)
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/* The USB 3.0 spec redefines bits 5:4 of bmAttributes as interrupt ep type. */
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#define USB_ENDPOINT_INTRTYPE 0x30
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#define USB_ENDPOINT_INTR_PERIODIC (0 << 4)
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@ -630,6 +635,20 @@ static inline int usb_endpoint_maxp(const struct usb_endpoint_descriptor *epd)
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return __le16_to_cpu(epd->wMaxPacketSize);
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}
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/**
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* usb_endpoint_maxp_mult - get endpoint's transactional opportunities
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* @epd: endpoint to be checked
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*
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* Return @epd's wMaxPacketSize[12:11] + 1
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*/
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static inline int
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usb_endpoint_maxp_mult(const struct usb_endpoint_descriptor *epd)
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{
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int maxp = __le16_to_cpu(epd->wMaxPacketSize);
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return USB_EP_MAXP_MULT(maxp) + 1;
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}
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static inline int usb_endpoint_interrupt_type(
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const struct usb_endpoint_descriptor *epd)
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{
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