Re: Linux USB file storage gadget with new UDC

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Hi,

>> However, the USB-2 spec says (section 9.2.6.4) that devices should be
>> able to carry out requests with no Data stage (such as Set-Config)
>> within 50 ms.  Does your gadget really take longer than that to handle
>> the exception?
>>
>> To find out, collect a usbmon trace showing what happens when your new
>> driver is plugged into a Linux host.
>>
>>>  I have set the NAK and
>>> stall the endpoint 0 after receiving Set-Config request, however,
>>
>> That doesn't make sense.  Stalling the endpoint means sending a STALL
>> packet.  You can't send both a STALL and a NAK.
>>
>>> Get-Config request is still sent out by USBCV host immediately.
>>
>> There should be at least a 50-ms delay, unless the UDC driver is doing
>> something wrong.
>
> The latest usbmon trace is attached. From the trace, the timing is
> within 50ms from Set-Config request to the next request.
>
>> Does your gadget really take longer than that to handle the exception?
> Yes, i think there is a delay before gadget calls the
> handle_exception() routine. So the problem is before
> handle_exception() of Set-Config request is called, the next request
> is sent out already by the host. So if the next request is Get-Config,
> it will not return the latest config value.

As can be seen in the gadget driver log below, after Set-Config
request is received, another two more requests are received before
handle_exception() is called. If there is a way to call
handle_exception() immediately after Set-Config request, it would be
very helpful.

g_file_storage gadget: ep0-setup, length 8:
00000000: 00 09 01 00 00 00 00 00
g_file_storage gadget: set configuration
and stall endpoint
g_file_storage gadget: ep0-setup, length 8:
00000000: 80 06 04 03 09 04 ff 00
g_file_storage gadget: get string descriptor
ept0 in queue len 0x1a, buffer 0xc1297800
ep0_complete
g_file_storage gadget: ep0-in, length 26:
00000000: 1a 03 53 00 65 00 6c 00 66 00 2d 00 70 00 6f 00
00000010: 77 00 65 00 72 00 65 00 64 00
g_file_storage gadget: ep0-setup, length 8:
00000000: 80 06 05 03 09 04 ff 00
g_file_storage gadget: get string descriptor
ept0 in queue len 0x1a, buffer 0xc1297800
ep0_complete
g_file_storage gadget: ep0-in, length 26:
00000000: 1a 03 4d 00 61 00 73 00 73 00 20 00 53 00 74 00
00000010: 6f 00 72 00 61 00 67 00 65 00
handle_exception begin
handle_exception wait until
handle_exception old_state 4
g_file_storage gadget: set interface 0
g_file_storage gadget: high-speed config #1
FSG_STATE_CONFIG_CHANGE 19 21 0
g_file_storage gadget: in handle_exception loop

Thanks,
victor
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