Commit e58dcebc authored Sep 25, 2008 by Alan Stern Committed by Greg Kroah-Hartman Oct 17, 2008

USB: UHCI: improve scheduling of interrupt URBs

This patch (as1140) adds a little intelligence to the interrupt-URB
scheduler in uhci-hcd. Right now the scheduler is stupid; every URB
having the same period is assigned to the same slot. Thus a large
group of period-N URBs can fill their slot and cause -ENOSPC errors
even when all the lower-period slots are empty.

With the patch, if an URB doesn't fit in its assigned slot then the
scheduler will try using lower-period slots. This will provide
greater flexibility. As an example, the driver will be able to handle
more than just three or four mice, which the current driver cannot.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

parent 925dff5d

drivers/usb/host/uhci-q.c

+11 −6

Original line number	Diff line number	Diff line
		@@ -1065,13 +1065,18 @@ static int uhci_submit_interrupt(struct uhci_hcd uhci, struct urb urb,
		}
		if (exponent < 0)
		return -EINVAL;

		/* If the slot is full, try a lower period */
		do {
		qh->period = 1 << exponent;
		qh->skel = SKEL_INDEX(exponent);

		/* For now, interrupt phase is fixed by the layout
		* of the QH lists. */
		* of the QH lists.
		*/
		qh->phase = (qh->period / 2) & (MAX_PHASE - 1);
		ret = uhci_check_bandwidth(uhci, qh);
		} while (ret != 0 && --exponent >= 0);
		if (ret)
		return ret;
		} else if (qh->period > urb->interval)

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