Re: Allocating buffers for USB transfers (again)

From: Daniel Mack
Date: Thu Aug 11 2011 - 19:40:47 EST

On 08/12/2011 01:29 AM, MatÄj Laitl wrote:
On 11.â8.â2011 Daniel Mack wrote:
On Thu, Aug 11, 2011 at 8:05 PM, Sarah Sharp
Because according to Matej, he applied that patch, plus my patch to
reject zero-length buffers[1], and he saw debugging that indicated he
*did* see zero-length buffers. Is there any chance your driver might
submit a zero-length buffer in the middle of the isochronous URB
transfer array?

Hmm, judging from the code, this can only ever happen if we receive an
inbound iso frame which has a valid status and an actual_length of
zero. Also, it was not neccessary to catch this case for EHCI.

Maetj, does this patch make any difference?

This patch actually makes the sound playback _worse_. Now I get strange
squawks where previously at least first seconds of a song sounded normally.

However, I no longer get "zero length buffer submitted" or that "... Weird."
debug messages, only several megabytes of: (should I post these somewhere?)

xhci_hcd 0000:05:00.0: Giveback URB ffff880114cec000, len = 880, expected =
1000, status = -115
xhci_hcd 0000:05:00.0: Giveback URB ffff880114740000, len = 352, expected =
1000, status = -115
xhci_hcd 0000:05:00.0: underrun event on endpoint

Might be the hardware doesn't like this. As I said, the patch is blindly written and I couldn't test it. Did you test this on a EHCI port as well?


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