From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933436AbdKBOOV (ORCPT ); Thu, 2 Nov 2017 10:14:21 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:54842 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S933034AbdKBOOU (ORCPT ); Thu, 2 Nov 2017 10:14:20 -0400 Date: Thu, 2 Nov 2017 10:14:19 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Roger Quadros cc: balbi@kernel.org, , , , "# v4 . 13+" Subject: Re: [PATCH v2][RESEND] usb: gadget: core: Fix ->udc_set_speed() speed handling In-Reply-To: <46a6dae0-b9f1-9d7b-d6c7-8f3c8f59ca6e@ti.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2 Nov 2017, Roger Quadros wrote: > On 01/11/17 17:45, Alan Stern wrote: > > On Wed, 1 Nov 2017, Roger Quadros wrote: > > > >>> Roger, would you like to send in a follow-up patch that removes the now > >>> unnecessary code from dummy_udc_set_speed() in dummy_hcd.c? > >>> > >> > >> Sure. I have a question though. > >> > >> In dummy_udc_set_speed() we should just set gadget.speed to whatever is passed in speed. > >> This will be the maximum supported speed by the gadget function driver. > > > > Following your patch, it will be the maximum speed supported by the > > gadget function driver or the maximum speed supported by the UDC > > driver, whichever is lower. That's the whole point of your patch, > > right? > > Yes. > > > > >> However, is it possible that the gadget will be connected at a lower speed than that? > > > > Yes, it is possible to connect at a speed lower than the function > > driver's maximum speed. The connection speed for dummy-hcd is > > controlled by a pair of module parameters: is_super_speed and > > is_high_speed. > > > >> I see gadget.speed being updated in dummy_hub_control() GetPortStatus: case, but not > >> in case of USB_SPEED_HIGH and USB_SPEED_LOW. > > > > Here's what the code does, in outline form: > > > > switch (dum_hcd->dum->gadget.speed) { > > case USB_SPEED_HIGH: > > ... > > break; > > case USB_SPEED_LOW: > > ... > > break; > > default: > > dum_hcd->dum->gadget.speed = USB_SPEED_FULL; > > break; > > } > > > > In other words, if gadget.speed isn't USB_SPEED_HIGH or USB_SPEED_LOW, > > set it to USB_SPEED_FULL. And this is all under the case where the > > connection is USB-2, not USB-3 or higher. > > > > How is this related to the requested change to dummy_udc_set_speed()? > > With or without the requested change to dummy_udc_set_speed() there will > never be a case when gadget.speed isn't already USB_SPEED_FULL > if connection is USB-2 and gadget.speed is not USB_SPEED_HIGH or USB_SPEED_LOW. > > So in the above code snippet, default: portion is redundant. > > But that can be fixed in a separate patch. Ah, I see. Yes, you can change this too if you want. Alan Stern