On Wed, 29 Jul 2009, Robin Callender wrote: > Hi all, > > I am working on a USB gadget driver for an audio device. Are you aware that there are at least two other audio gadget implementations in the works? Search through the mailing list archives. > My reference spec is the "USB Device Class Definition for Audio Devices". > I have the basic guts of the driver now, modeled after the gmidi gadget. > But there is one part I am quite unhappy with: in particular the receiving > of OUT data over ep0 for a setup-type transaction. > As you may know, for Audio "SET_x" control operations, there is usually data > carried as OUT phase, in addition to the standard w_* params received on the > setup phase. > For example, SET_CUR(volume) carries the new volume control value in the > OUT phase of the setup transaction. You probably mean "data stage", not "OUT phase" (see 8.5.3 in the USB 2.0 spec). > Basically I would like to know what the recommended model or coding pattern > is for receiving OUT data during the setup callback. > I have reviewed all the gadget drivers, but none appear to address this > area, or I am missing something. > Are there any sample sources or code snippets to act as a guide in this > area? The kerneldoc for usb_ep_queue() in include/linux/usb/gadget.h discusses this, but somewhat briefly. In drivers/usb/gadget/file_storage.c:class_setup_req(), the USB_CBI_ADSC_REQUEST case handles a control-OUT transfer. Look in fsg_setup() to see how this is done. Basically you just submit a usb_request for ep0 to receive the OUT data. 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
