On Thu, 10 Feb 2011, Chris Furlough wrote: > Hey guys, this should be a simple question. (I hope) > > I'm using usb_control_msg to issue a "Memory Request" from my usb audio > device. (In adherence with the USB Device Class Definition for Audio > Devices release 2.0 spec section 5.2.7.1 to be exact). > > I issue a usb_control_msg in the READ direction, and I provide *data > pointing to a buffer to accept the data, and I provide wLength which is > the size of this buffer. > > When I do this, the response is ALWAYS wLength, regardless of the data > size. Is this correct? Depends on what you mean. When you say the response is wLength, do you mean that usb_control_msg returns a value equal to wLength? Or do you mean that the device somehow sends a buffer containing the value of wLength? Or do you mean that the device sends a buffer whose length is wLength? usb_control_msg works correctly, so whatever it returns is what the transfer actually did. > Or should the device return the data that is has, and return the size of > that data instead of wLength every time? I don't know what the device is supposed to do. Doesn't the Audio class specification say? 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
