[Bug 220748] usb: xhci_queue_isoc_tx_prepare ignore start_frame and always assumes URB_ISO_ASAP is set

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=220748

--- Comment #8 from Alan Stern (stern@rowland.harvard.edu) ---
Sorry, yes, urb->interval and urb->start_frame do get modified during
submission.  Drivers are allowed to read those fields before the URB completes.

The documentation from Intel is irrelevant.  It discusses the xHCI hardware,
but we're talking about the Linux software interface.

As for the considerations at the start of this bug report...  xhci-hcd is
indeed supposed to ignore urb->start_frame during submission and overwrite it
with the actual starting (micro)frame number.  And most of the time, xhci-hcd
is supposed to ignore URB_ISO_ASAP.  But it's not supposed to ignore
URB_ISO_ASAP in cases where the URB was submitted too late.  By "too late", I
mean that at the time the URB was submitted, the (micro)frame that it should
have been scheduled for -- one period after the last frame of the preceding URB
-- had already elapsed.

-- 
You may reply to this email to add a comment.

You are receiving this mail because:
You are watching the assignee of the bug.