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[media] gspca - main: Correct use of interval in bandwidth calculation 

The calculated bandwidth should not be multiplied by the interval, but be
divided by it. Also bInterbval should be interpreted as a power of 2
for isochronous endpoints.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Hans de Goede 2011-12-30 08:20:50 -03:00 committed by Mauro Carvalho Chehab
parent 66957b8646
commit d0d3435b21
1 changed files with 6 additions and 1 deletions
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7
drivers/media/video/gspca/gspca.c
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@ -698,12 +698,17 @@ static int build_isoc_ep_tb(struct gspca_dev *gspca_dev,
USB_ENDPOINT_XFER_ISOC);
if (ep == NULL)
continue;
if (ep->desc.bInterval == 0) {
pr_err("alt %d iso endp with 0 interval\n", j);
continue;
}
psize = le16_to_cpu(ep->desc.wMaxPacketSize);
psize = (psize & 0x07ff) * (1 + ((psize >> 11) & 3));
bandwidth = psize * ep->desc.bInterval * 1000;
bandwidth = psize * 1000;
if (gspca_dev->dev->speed == USB_SPEED_HIGH
|| gspca_dev->dev->speed == USB_SPEED_SUPER)
bandwidth *= 8;
bandwidth /= 1 << (ep->desc.bInterval - 1);
if (bandwidth <= last_bw)
continue;
if (bandwidth < ep_tb->bandwidth) {