From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 03736C433EF for ; Mon, 27 Jun 2022 14:54:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236998AbiF0OyU (ORCPT ); Mon, 27 Jun 2022 10:54:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35412 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235197AbiF0OyR (ORCPT ); Mon, 27 Jun 2022 10:54:17 -0400 Received: from netrider.rowland.org (netrider.rowland.org [192.131.102.5]) by lindbergh.monkeyblade.net (Postfix) with SMTP id C053915839 for ; Mon, 27 Jun 2022 07:54:15 -0700 (PDT) Received: (qmail 121138 invoked by uid 1000); 27 Jun 2022 10:54:14 -0400 Date: Mon, 27 Jun 2022 10:54:14 -0400 From: Alan Stern To: Neal Liu Cc: Felipe Balbi , Greg Kroah-Hartman , Roger Quadros , Miaohe Lin , Wesley Cheng , "Eric W . Biederman" , Matthew Wilcox , Nikita Yushchenko , Cai Huoqing , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" , BMC-SW Subject: Re: [PATCH v2] usb: gadget: f_mass_storage: Make CD-ROM emulation works with Windows OS Message-ID: References: <20220624021916.318067-1-neal_liu@aspeedtech.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 27, 2022 at 02:56:40AM +0000, Neal Liu wrote: > > On Fri, Jun 24, 2022 at 10:19:16AM +0800, Neal Liu wrote: > > > Add read TOC with format 1 to support CD-ROM emulation with Windows > > > OS. > > > This patch is tested on Windows OS Server 2019. > > > > > > Signed-off-by: Neal Liu > > > --- > > > drivers/usb/gadget/function/f_mass_storage.c | 5 +++-- > > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/usb/gadget/function/f_mass_storage.c > > > b/drivers/usb/gadget/function/f_mass_storage.c > > > index 3a77bca0ebe1..9edf76c22605 100644 > > > --- a/drivers/usb/gadget/function/f_mass_storage.c > > > +++ b/drivers/usb/gadget/function/f_mass_storage.c > > > @@ -1209,7 +1209,8 @@ static int do_read_toc(struct fsg_common > > > *common, struct fsg_buffhd *bh) > > > > > > switch (format) { > > > case 0: > > > - /* Formatted TOC */ > > > + case 1: > > > + /* Formatted TOC, Session info */ > > > > This comment is a little misleading. 0 is formatted TOC, and 1 is > > multi-session info. The way you wrote it, it looks like the comment applies to > > both formats. Do it like this: > > > > case 0: /* Formatted TOC */ > > case 1: /* Multi-session info */ > > > > Okay, looks more clear. I'll fix it in next patch. > > > > len = 4 + 2*8; /* 4 byte header + 2 descriptors */ > > > memset(buf, 0, len); > > > buf[1] = len - 2; /* TOC Length excludes length field */ > > > > It looks like you ignored one of the problems I pointed out in my earlier email: > > > > > When format is 1, the driver is supposed to ignore the start_track > > > value. Your patch does not do this. > > > > Please fix this. > > > > Do you mean ignore the "start_track > 1" above? Yes, that's what I mean. > Do this check only for format 0? Or format 0 & 2? According to the MMC spec, the Track/Session Number is ignored for format 1. For format 0 it is valid as a Track Number, and for format 2 it is valid as a Session Number. Therefore it should be checked for formats 0 and 2 but not for format 1. Alan Stern