[linux-dvb] allocate memory for USB URB-buffers

[Patrick Boettcher <patrick.boettcher@desy.de>]

Hi list,

I would like to know which is the common way to allocate memory for the 
urb-buffer for the USB MPEG-TS-transfer?

Currently I use pci_alloc_consistent (which I copy'n'pasted from 
ttusb-dec, when I started working on usb drivers). It is working quite 
well, but with USB2.0 dibusb-devices (eg NOVA-T USB2) there is a problem 
sometimes:

DiBcom specifies a bulk-transfer-buffersize of 210*188 (39480) bytes in 
their usb2.0-firmware. I.e. I have to use a buffer of almost 40KB for each 
URB. Normally I submit 3 URBs, therefore I have to alloc 120KB. This is 
what fails sometimes:

insmod: page allocation failure. order:4, mode:0x21

I assume this means it is not possible to get free, continous 120KB. 
Sometimes this even fails with 40KB... (1 URB for test reasons).

If I just reduce the size of the URB Buffer, the device is crashing and 
the system with it.

Is there a reason why one can't use kmalloc(ATOMIC)? Will it fail as well?

Thanks in advance for enlightening me,
Patrick.

--
  Mail: patrick.boettcher@desy.de
  WWW:  http://www.wi-bw.tfh-wildau.de/~pboettch/