Hello everyone
I'm trying to make a driver that, for now, just answers depending
on what is sent OUT from the host.
The problem is that apparently gadgetfs has a queue with the
usb_requests. So whatever I send to the driver I get the answer after
asking 2 or 3 times, i.e., I have to make two or three IN bulk transfers to get
what I want.
I did some simple modifications to the usb.c example driver found in
linux-usb.org. I used a global variable to access it from both threads:
static char *buffer;
In empty_out_buf function I do a simple switch to assing value to the
global buffer depending on the value sent out by the host:
switch (((char *)buf)[0]) {
case 0x01:
printf("case 0x01\n");
memset(buffer, '1', nbytes);
break;
case 0x02:
printf("case 0x02\n");
memset(buffer, '2', nbytes);
break;
default:
printf("case default\n");
memset(buffer, 'd', nbytes);
break;
}
The other modification was in simple_source_thread function. Where
the "buffer" variable created by me is sent instead of the local
buf variable:
status = write(source_fd, buffer, USB_BUFSIZE);
I'm using libusb to test on the host side, with the following functions:
libusb_bulk_transfer (devHandle, BULK_OUT, buffer, bufferSize,
&transferred, 500);
libusb_bulk_transfer (devHandle, BULK_IN, buffer, bufferSize,
&transferred, 500);
When using a buffer size of 511 bytes or less until the third IN
bulk transfer I get, e.g., in case 0x01 the '1' I assigned before.
When the buffer size is of 512 or more I get the assigned value
in the second transfer.
Here is the usbmon trace, USB_BUFSIZE 511:
f2adf880 32307.036783 S Bi:1:090:1 - 511 <
f2adf880 32307.036843 C Bi:1:090:1 0 511 = 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
f2a78100 32333.300397 S Bo:1:090:1 - 511 = 01010101 01010101 01010101 01010101 01010101 01010101 01010101 01010101
f2a78100 32333.300472 C Bo:1:090:1 0 511 >
f2a30500 32349.364816 S Bi:1:090:1 - 511 <
f2a30500 32349.364975 C Bi:1:090:1 0 511 = 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
f2ba3400 32350.468457 S Bi:1:090:1 - 511 <
f2ba3400 32350.468601 C Bi:1:090:1 0 511 = 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
f2a97680 32351.268549 S Bi:1:090:1 - 511 <
f2a97680 32351.268600 C Bi:1:090:1 0 511 = 31313131 31313131 31313131 31313131 31313131 31313131 31313131 31313131
USB_BUFSIZE 512:
f2b86600 35192.622809 S Bi:1:091:1 - 512 <
f2b86600 35192.622879 C Bi:1:091:1 0 512 = 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
f2bd2280 35196.388595 S Bo:1:091:1 - 512 = 01010101 01010101 01010101 01010101 01010101 01010101 01010101 01010101
f2bd2280 35196.388756 C Bo:1:091:1 0 512 >
f6612080 35198.996722 S Bi:1:091:1 - 512 <
f6612080 35198.996754 C Bi:1:091:1 0 512 = 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
f2922680 35200.028271 S Bi:1:091:1 - 512 <
f2922680 35200.028381 C Bi:1:091:1 0 512 = 31313131 31313131 31313131 31313131 31313131 31313131 31313131 31313131
I've also noticed that when "usb" binary it first initialized it calls
fill_in_buf function (1 or 2 depending on the buffer size as specified
before).
Is there a form to flush the queue? Or how can I access
the information I want right in the next transfer?
Thanks for your help,
Aldo Brett
--
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
