On 06/23/2013 07:05 PM, Alan Stern wrote:
That's why, if the check is checked, I feel it should be added to each
HCD driver separately. Maybe I'm wrong. But before doing anything,
you should check with Thomas Pugliese. He recently added SG support to
the wireless USB driver.
Suppose wireless USB is one exception, it should the only one, so we can
rule it out easily by using hcd->wireless, right?
Yes, that's true.
Alan Stern
This test passed for many years. It became to fail only for the recent
kernels. So this event looks like a broken thing.
It's not a good idea to force a higher driver to care about the max pkt
size in a dynamically selected usb configuration. Note that a sg-list
could be created even in another subsystem.
If we decided to treat such sg-lists as acceptable, then we have only
two options:
1. Send a shorter packet between two full packets of a TD list.
2. Introduce a bounce buffer similarly in lib/swiotlb.c
Option 2 is very costed. If the option 1 is acceptable, then we should
choose it.
But ehci does resolve this issue in such way already, so the option 1 is
acceptable.
From my point of view this choice is unrelated to the wireless USB
requirements.
Konstantin Filatov
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