[linux-dvb] m920x device: Genius TVGo DVB-T02Q

Antti Palosaari crope at iki.fi
Thu Dec 13 17:54:56 CET 2007


hi,
Looks like it is almost working :)

Román wrote:
> .stream = {
> 	.type = USB_ISOC,
> 	.count = 6,
> 	.endpoint = 0x81,
> 	.u = {
> 		.isoc = {
> 			.framesperurb = 1,
> 			.framesize = 564,
> 			.interval = 150,
> 		}
> 	}
> },
> 
> 
>  Be aware that lsusb -v (without ehci_usb) lists 1023 as the maximum
> packet size, as opposed to 564 (the value with ehci_usb loaded), but
> changing that parameter didn't make any difference. Also note the
> value in .interval: I only got some success with values between 100
> and 200, approximately. I'm not an expert but they seem very strange
> values to me. Didn't have any success at all with ehci_usb loaded.

There is not many drivers using isoc currently, only au6610 and ttusb2. 
When I did au6610 it was was also hard to guess those values. I don't 
know whats the "correct" way to find values, but here is method I used 
(au6610.c):

.framesperurb = 40,
from usbsnoop.log
NumberOfPackets      = 00000028

.framesize = 942,
from lsusb
wMaxPacketSize     0x03ae  1x 942 bytes
or from usbsnoop.log
IsoPacket[1].Offset = 942

.interval = 1.25,   /* 125 us */
Interface[0]: Pipes[1] : Interval          = 0x00000001
Interface[0]: Pipes[1] : PipeType          = 0x00000001 
(UsbdPipeTypeIsochronous)

I don't remember where I found 125 us, maybe looking times from 
usbsnoop.log. Anyhow, looks like it is wrong but still works just fine 
because 1.25 is rounded to 1 due to integer.

I hope this helps :)

regards
Antti

-- 
http://palosaari.fi/




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