Hello everyone,
I currently have a driver that has 1024 byte endpoint buffers (bulk
transfer) and it is running on the AT91RM9200. I am running 2.6.12, but
I looked at the kernel git tree head(2.6.20) at91_udc.c code and it has
the same issue. My gadget can accept data from the host and the data
will be any amount.
If data is transmitted from the host and its length is 960 bytes lets
say, the read_fifo() does not call done() because the length of the last
transfer is 64 bytes and the 1024 byte buffer is not yet full so is_done
is set to zero (below).
code snippet, at91_udc.c::read_fifo():
req->req.actual += count;
is_done = (count < ep->ep.maxpacket);
if (count == bufferspace)
is_done = 1;
PACKET("%s %p out/%d%s\n", ep->ep.name, &req->req, count, is_done ? "
(done)" : "");
/*
* avoid extra trips through IRQ logic for packets already in
* the fifo ... maybe preventing an extra (expensive) OUT-NAK
*/
if (is_done)
done(ep, req, 0);
end snippet;
If I run "cat /proc/driver/udc", I see a request sitting with 960/1024
bytes used. Upon the completion of the next transfer, the first
transfer will then be sent as done() will be called.
So I have changed my host program to check and see if the data size
being sent to the gadget is divisible by 64 (size % 64 == 0). If it is,
then I add a small chunk so that the driver will handle it correctly and
the data will be processed upon transfer completion.
I hate this fix, but it is the only one I can think of, anybody have a
better way of fixing this issue? I looked at the driver and could not
come up with an elegant solution to this.
Regards,
Jeff Warren
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