Hi, At libfreenect2 we are interested in using large buffers for isochronous transferring of large depth camera frames.
proc_do_submiturb() hardcodes two limits for iso transfers: 128 packets per URB, and 49152 per packet. When I submit a large URB of 128 packets of 49152 bytes I will have ENOMEM, because this URB allocates a buffer of 128*49152 (6MiB) and it is too large for kmalloc. The problem is userspace has no good way of querying the maximum acceptable size by kmalloc and consequently doesn't know how large a transfer is known to work with the kernel. Actually the 6MiB URB is created via libusb, which tries to split my even larger iso transfer into smaller URBs. The best libusb can do is use the 128/49152 limits from the kernel and splits my transfer into 6MiB URBs (and does not work). How to approach this problem? Is there a recommended max transfer size for kmalloc somewhere in the USB core? Should the packet number limit be lowered for iso transfer? Can the kmalloc limit be queried? Regards, Lingzhu -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
