On Thu, 23 Jul 2009, Madhavi Manchala wrote: > Dear Alan, > > Thanks for the information. > > I overlooked the **preq in the alloc_request() function. I understand > it now a little bit more. > > I have been modifying the file storage gadget driver code to handle > the multiple commands from a few days. As a part of this, first I have > implemented the three threads as shown below. > > main thread > | > | > --------------------- > | | > Thread-1 Thread-2 > > The idea behind it is, the main thread queues the commands and wakeups > the thread-1 (currently I have created only main thread and thread-1). > Then the thread-1 do the remaining functionality. > > main thread functionality > ----------------------------------- > > 1) Invokes the get_next_command and waits for the command. > 2) This will be signaled from completion callback function. > 3) Then, queues the command. > 4) Wakeups the thread-1 to process command. > 5) Again, sleeps to get the next command. You don't need a separate thread to do this. Just let the completion callback function queue the command and wake up thread-1. > thread-1 functionality > ------------------------------ > 1) This thread will be started from the fsg_bind function and waits to > receive a signal from the main thread. > 2) After wakeup from the main thread, it performs the do_scsi_command, > finish_reply and send_status functionality. > 3) Again, sleeps to wake from the main thread. > > After doing the above modifications, the file_storage gadget driver > works fine without any issues. > > However, I need some clarifications for the following. > > 1) Is it possible to handle the multiple commands in the gadget driver > code if we do the modifications as said above without doing any > modifications to the dummy_hcd driver at all. Ofcourse, if the mass > storage driver sends the multiple commands. No changes should be needed in dummy-hcd. > 2) I would like to wake up thread-2 from main thread when ever there > is a next command to process (at this time thread-1 is busy processing > first command). I guess, to handle like this, I need to create > different buffer heads for each thread. Am I correct? Well, you will certainly want to have more than two buffer heads. Two per thread ought to be enough. > Is there any > different approach to handle multiple commands? You could handle them one at a time, in a single thread. Or you could figure out how to do all the I/O in interrupt context, by calling the block layer directly. Alan Stern -- 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
