[linux-dvb] Technisat AirStar 2 USB in kernel 2.6.21?

Jan Wagner jwagner at cc.hut.fi
Sat Jun 9 14:07:52 CEST 2007

Well, figured it out after digging through the kernel USB core and 
hci source code:

On Sat, 9 Jun 2007, Jan Wagner wrote:
> The usb dvb-t receiver works just fine in WinXP, but in linux I get this 
> error in dmesg:
>  flexcop_usb: submitting urb 0 failed with -28.
> and the receiver doesn't work, and /dev/dvb/adapter0 is not even created. 
> Which is strange.
> The error -28 perhaps is -ENOSPC, "no space left on device". At least per 'df 
> -h' there is plenty of free space on all mounts, so maybe this "space" is 
> lacking somewhere else. (?)

Obviously ;) the ENOSPC (-28) error number in linux USB is taken to be 
(#define) USB_ST_BANDWIDTH_ERROR which is returned when kernel believes 
there is not sufficiently bandwidth available to submit the urb/data.

Anyway. Moved the AirStar 2 to a different USB port and hey presto it 
works! :-)

In some posting from late 2005 it was said that the kernel's USB 
bandwidth estimator is somewhat buggy and should be disabled in a kernel 
compile. Well in 2.6.21 the estimator still seems buggy, but now the 
option to disable it has been disabled. Duh! :-)

Still not quite sure why, with the same 4-port USB 2.0 hub having 
keyboard, wireless mouse (both very high speed of course ;) and then 
USB1.1 AirStar 2 attached makes the linux kernel think there's not enough 
bandwidth. In WinXP the same configuration works fine. Anyway, AirStar on 
different USB port in Linux seems to work now. Phew.

  - Jan

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