On 19/09/2020 16.54, M. Vefa Bicakci wrote:
On 18/09/2020 18.49, Shuah Khan wrote:
On 9/18/20 8:31 AM, M. Vefa Bicakci wrote:
Hello Shuah,
I have just cleaned up the patches and run usbip_test.sh with a kernel without
the patches in this series and with a kernel in this series.
I noticed that there is a change in behaviour due to the fact that the new
match function (usbip_match) does not always return true. This causes the
stub device driver's probe() function to not get called at all, as the new
more selective match function will prevent the stub device driver from being
considered as a potential driver for the device under consideration.
Yes. This is the behavior I am concerned about and hence the reason
to use the usbip test to verify this doesn't happen.
With the patch you have the usbip match behavior becomes restrictive
which isn't desirable.
All of this results in the following difference in the logs of the usbip_test.sh,
where the expected kernel log message "usbip-host 2-6: 2-6 is not in match_busid table... skip!"
is not printed by a kernel that includes the patches in this series.
--- unpatched_kernel_log.txt 2020-09-18 17:12:10.654000000 +0300
+++ patched_kernel_log.txt 2020-09-18 17:12:10.654000000 +0300
@@ -213,70 +213,69 @@
|__ Port 1: Dev 2, If 0, Class=Human Interface Device, Driver=usbhid, 480M
==============================================================
modprobe usbip_host - does it work?
Should see -busid- is not in match_busid table... skip! dmesg
==============================================================
-usbip-host 2-6: 2-6 is not in match_busid table... skip!
==============================================================
Do you find this change in behaviour unacceptable?
Yeah. This behavior isn't acceptable.
If no, I can remove this
test case from usbip_test.sh with the same patch. If yes, then there is a need
for a different solution to resolve the unexpected negative interaction between
Bastien's work on generic/specific USB device driver selection and usbip
functionality.
I would recommend finding a different solution. Now that you have the
usbip test handy, you can verify and test for regressions.
thanks,
-- Shuah
Thanks for the feedback, Shuah. I spent some time looking at and instrumenting
the code in an attempt to find another solution, but have not found one.
If the generic/specific USB driver selection functionality that Bastien Nocera
introduced is desired to stay in the kernel, then making usbip_match more
specific appears to be the only option for usbip to be functional without
negatively affecting other device drivers.
Should Bastien's work be reverted until a solution to this issue is found?
Would you (or anyone) have any suggestions? I would be happy to work further
on resolving this issue.
Hello again,
Status update: I found a solution that should be more acceptable. It involves
some changes to the generic/specialized driver selection code and the removal
of usbip_match altogether, while preserving proper behaviour of the usbip driver,
apple-mfi-fastcharge and dummy_hcd. I intend to publish a new patch set by
tomorrow.
Vefa
