Hi, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes: >> Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes: >> > On Tue, 6 Jun 2017, Felipe Balbi wrote: >> > >> >> Sometimes, the gadget driver we want to run has max_speed lower than >> >> what the UDC supports. In such situations, UDC might want to make sure >> >> we don't try to connect on speeds not supported by the gadget >> >> driver (e.g. super-speed capable dwc3 with high-speed capable g_midi) >> >> because that will just fail. >> >> >> >> In order to make sure this situation never happens, we introduce a new >> >> optional ->udc_set_speed() method which can be implemented by >> >> interested UDC drivers. >> >> >> >> Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx> >> > >> > dummy-hcd already checks for this in its dummy_pullup() routine. >> > Should other UDC drivers copy this approach? >> >> sounds like a layer violation to me :-s You're basically relying on the >> fact the the UDC (dummy, dwc3, chipidea, musb, etc) have access to a >> pointer to the usb_gadget_driver currently running. If that changes - >> and it's not too farfectched of a change, since UDC doesn't need to know >> which gadget driver is running - dummy may break. I would rather patch >> dummy a bit to implement ->udc_set_speed(). >> >> What do you think? > > Well, it wasn't a layering violation back in the days of the original > gadget stack. But the design has changed over time, and I take your > point. > > Currently, dummy_hcd uses the following fields from the gadget driver > structure: the disconnect, suspend, resume, and setup callbacks, and > the max_speed and function values (the last is only for a sysfs entry). > It seems reasonable to move all these things into the UDC core. Thank you. I'll patch dummy to implement ->udc_set_speed(). I'll also have a look at dummy's sysfs entries. cheers -- balbi -- 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
