Hi All, I am trying to understand how usb.c, the only working user mode driver example that I found on the net that uses gadgetfs. Using that code as the base I am trying to write a HID keyboard driver (user mode) with Net2280 peripheral device controller to simulate working of a keyboard. I referred to the following discussion that happened almost half a decade ago but didn't lead to any useful conclusions (but did help me find answers to some of my questions): http://www.mail-archive.com/linux-usb-devel@xxxxxxxxxxxxxxxxxxxxx/msg20380.html I am running Wireshark with USB support on the host to see what's going on. I've attached the traces of real keyboard and my simulation keyboard with this email. Based on that I have the following (newbie) questions: 1. After the response to 'GET DEVICE DESCRIPTOR' request, the trace of simulation driver shows that the host sends a 'GET DESCRIPTOR DEVICE QUALIFIER' request. I do not see such request in the trace for the real keyboard. What is the meaning of this request? Was the response to the earlier 'GET DEVICE DESCRIPTOR' request malformed (the sniffer doesn't indicate that, however)? Simulation keyboard trace: -------------------------------------------------------------------------------------------------- Source Destination Protocol Info -------------------------------------------------------------------------------------------------- host 23.0 USB GET DESCRIPTOR Request DEVICE QUALIFIER 2. My simulation keyboard driver stops responding after the following request: ------------------------------------------------------------------------------- Source Destination Protocol Info ------------------------------------------------------------------------------- host 3.0 USB SET CONFIGURATION Request What should my driver send as a response back to the host? I saw that the real keyboard just sends a response with 0's filled in it. Is this what it is supposed to send? Keyboard simulator creates a new thread for 'ep-a' management and writes the endpoint descriptor into ep-a's file descriptor. But the host doesn't seem to get it (can't see it on Wireshark). What I see is a (probable) timeout after 5 sec and 0's filled in 'SET CONFIGURATION' response. Also after this, the host doesn't send a request for reports, like it does in case of the real keyboard. Why does this happen? 3. The real keyboard has an IN endpoint of type interrupt. As far as I understand, this is the endpoint that should be sending the report descriptors to the host. However, in Wireshark I see that when the host sends a 'GET DESCRIPTOR RPIPE' request the ep0 of the real keyboard sends the report instead of ep1. Here is the trace (I assume '3.0' means ep0): ------------------------------------------------------------------------------------- Source Destination Protocol Info ------------------------------------------------------------------------------------- host 3.0 USB GET DESCRIPTOR Request RPIPE Since ep1 is interrupt type, shouldn't it send the report when the host sends an 'IN' token packet to ep0 instead of ep0 sending it when the host sends 'GET DESCRIPTOR RPIPE' to ep0? 4. Is there any other documentation available on gadgetfs and usb.c apart from the source code itself? Thanking you in advance. Regards, Aniruddha -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
