[Linux-usb-users] usb_control_msg() paramater values

tim bisson Sun, 26 Dec 2004 23:15:00 -0800

I'm learning how to write a USB device driver using delcom's USB 6 Digit Numeric Display device. I've been following the example from drivers/usb/misc/usbled.c and from someone's device driver implementation of delcom's usb numeric display (http://sourceforge.net/project/showfiles.php?group_id=106606). After reading source code and delcom's manual for several hours, I still can't figure out where some of the parameter values in usb_control_msg() come from.

usb_control_msg() prototype: |int *usb_control_msg *|(struct usb_device * dev, unsigned int pipe, __u8 request, __u8 requesttype, __u16 value, __u16 index, void * data, __u16 size, int timeout);

My question is this: How are the /request, //requesttype, value, /and/ index/ values figured out for a particular USB device?

I've looked at chapter 9.3 in the "Universal Serial Bus Specification" (www.scaramanga.co.uk/stuff/qemu-usb/usb11.pdf) document which specifies some standard device requests in table 9-3, but neither requesttypes in the examples below (0xc8 or 0x48) are listed in table 9-3.

usb_control_msg() examples -
usbled.c:
retval = usb_control_msg(led->udev,
               usb_sndctrlpipe(led->udev, 0),
               0x12,
               0xc8,
               (0x02 * 0x100) + 0x0a,
               (0x00 * 0x100) + color,
               buffer,
               8,
               2 * HZ);

delcom_device_driver.c
retval = usb_control_msg(pck->udev,
                usb_sndctrlpipe(pck->udev, 0),
                0x12,
                0x48,   // this has to be 0x48 to send data in the buffer
                (pck->minor * 0x100) + 0x0a,
                (pck->msb * 0x100) + pck->lsb,
                buffer,
                pck->length,
                1 * HZ);

Any help in figuring out how these paramater values are found out is appreciated.

Thanks,
Tim

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[Linux-usb-users] usb_control_msg() paramater values

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