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USB: EHCI: simplify isochronous scanning

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This patch (as1587) simplifies ehci-hcd's scan_isoc() routine by
eliminating some local variables, declaring boolean-valued values as
bool rather than unsigned, changing variable names to make more sense,
and so on.

The logic at the end of the routine is cut down significantly.  The
scanning doesn't have to catch up all the way to where the hardware
is; it merely has to catch up to where the hardware was when the last
interrupt occurred.  If the hardware has made more progress since then
and issued another interrupt, a rescan will catch up to it.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alan Stern 2012-07-11 11:23:07 -04:00 • committed by Greg Kroah-Hartman
parent 18aafe64d7
commit f428907822
3 changed files with 32 additions and 91 deletions
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3
drivers/usb/host/ehci-hcd.c
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@ -488,9 +488,6 @@ static int ehci_init(struct usb_hcd *hcd)
else // N microframes cached
ehci->i_thresh = 2 + HCC_ISOC_THRES(hcc_params);
ehci->next_uframe = -1;
ehci->clock_frame = -1;
/*
* dedicate a qh for the async ring head, since we couldn't unlink
* a 'real' qh without stopping the async schedule [4.8]. use it