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usb-ohci: td.cbp incorrectly updated near page end 

The current code that updates the cbp value after a transfer looks like this:
td.cbp += ret;
if ((td.cbp & 0xfff) + ret > 0xfff) {
	<handle page overflow>
because the 'ret' value is effectively added twice the check may fire too early
when the overflow hasn't happened yet.

Below is one of the possible changes that correct the behavior:

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Andriy Gapon 2011-12-22 11:34:30 +02:00 committed by Gerd Hoffmann
parent c75fead66e
commit fd891c9318
1 changed files with 3 additions and 3 deletions
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6
hw/usb-ohci.c
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@ -1025,10 +1025,10 @@ static int ohci_service_td(OHCIState *ohci, struct ohci_ed *ed)
if (ret == len) {
td.cbp = 0;
} else {
td.cbp += ret;
if ((td.cbp & 0xfff) + ret > 0xfff) {
td.cbp &= 0xfff;
td.cbp |= td.be & ~0xfff;
td.cbp = (td.be & ~0xfff) + ((td.cbp + ret) & 0xfff);
} else {
td.cbp += ret;
}
}
td.flags |= OHCI_TD_T1;