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 X-Spam-Level: X-Spam-Status: No, score=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 231D0C07E96 for ; Tue, 6 Jul 2021 16:29:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E92EC61C25 for ; Tue, 6 Jul 2021 16:29:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230137AbhGFQbw convert rfc822-to-8bit (ORCPT ); Tue, 6 Jul 2021 12:31:52 -0400 Received: from relay11.mail.gandi.net ([217.70.178.231]:56745 "EHLO relay11.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229935AbhGFQbv (ORCPT ); Tue, 6 Jul 2021 12:31:51 -0400 Received: (Authenticated sender: miquel.raynal@bootlin.com) by relay11.mail.gandi.net (Postfix) with ESMTPSA id D93D7100004; Tue, 6 Jul 2021 16:29:09 +0000 (UTC) Date: Tue, 6 Jul 2021 18:29:08 +0200 From: Miquel Raynal To: Guenter Roeck Cc: Tudor.Ambarus@microchip.com, michael@walle.cc, linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, richard@nod.at, vigneshr@ti.com Subject: Re: [PATCH] mtd: core: handle flashes without OTP gracefully Message-ID: <20210706182908.3cf82669@xps13> In-Reply-To: <2716acf0-fcf1-d2ef-83be-152d0300d687@roeck-us.net> References: <20210702093841.32307-1-michael@walle.cc> <9bb2acac-aeb8-d2b2-8df0-9acfd972ec5d@microchip.com> <9F46D75C-D00D-4577-A337-7411049EC7D9@walle.cc> <8da3d84e-dfbf-2030-98b4-148362d22f52@microchip.com> <2716acf0-fcf1-d2ef-83be-152d0300d687@roeck-us.net> Organization: Bootlin X-Mailer: Claws Mail 3.17.7 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Guenter, Guenter Roeck wrote on Sat, 3 Jul 2021 10:26:06 -0700: > On 7/3/21 9:42 AM, Tudor.Ambarus@microchip.com wrote: > > On 7/3/21 7:08 PM, Michael Walle wrote: > >> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe > >> > >> Am 3. Juli 2021 11:56:14 MESZ schrieb Tudor.Ambarus@microchip.com: > >>> On 7/2/21 12:38 PM, Michael Walle wrote: > >>>> EXTERNAL EMAIL: Do not click links or open attachments unless you > >>> know the content is safe > >>>> > >>>> There are flash drivers which registers the OTP callbacks although > >>> the > >>>> flash doesn't support OTP regions and return -ENODATA for these > >>>> callbacks if there is no OTP. If this happens, the probe of the whole > >>> > >>> why do they register the OTP callback if they don't support OTP? > >> > >> I don't know. But I certainly won't touch that code :p > > > > why? :D > > > >> > >> > >>>> flash will fail. Fix it by handling the ENODATA return code and skip > >>>> the OTP region nvmem setup. > >>>> > >>>> Fixes: 4b361cfa8624 ("mtd: core: add OTP nvmem provider support") > >>>> Reported-by: Guenter Roeck > >>>> Signed-off-by: Michael Walle > >>>> --- > >>>> drivers/mtd/mtdcore.c | 10 ++++++++-- > >>>> 1 file changed, 8 insertions(+), 2 deletions(-) > >>>> > >>>> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c > >>>> index b5ccd3037788..6881d1423dd6 100644 > >>>> --- a/drivers/mtd/mtdcore.c > >>>> +++ b/drivers/mtd/mtdcore.c > >>>> @@ -880,7 +880,10 @@ static int mtd_otp_nvmem_add(struct mtd_info > >>> *mtd) > >>>> > >>>> if (mtd->_get_user_prot_info && mtd->_read_user_prot_reg) { > >>>> size = mtd_otp_size(mtd, true); > >>>> - if (size < 0) > >>>> + /* ENODATA means there is no OTP region */ > >>>> + if (size == -ENODATA) > >>> > >>> If no OTP data, maybe it's more appropriate for the clients to just > >>> return a retlen of 0. > >> > >> you mean already checking ENODATA in mtd_otp_size() and return 0. That would also make the hunk below unnecessary. I'll change it. > > > > I've thought about: > > > > diff --git a/drivers/mtd/chips/cfi_cmdset_0001.c b/drivers/mtd/chips/cfi_cmdset_0001.c > > index 54f92d09d9cf..9419b33d7238 100644 > > --- a/drivers/mtd/chips/cfi_cmdset_0001.c > > +++ b/drivers/mtd/chips/cfi_cmdset_0001.c > > @@ -2314,7 +2314,7 @@ static int cfi_intelext_otp_walk(struct mtd_info *mtd, loff_t from, size_t len, > > > /* Check that we actually have some OTP registers */ > > if (!extp || !(extp->FeatureSupport & 64) || !extp->NumProtectionFields) > > - return -ENODATA; > > + return 0; > > > > There are various places where this is called, including code returning information > to userspace. That means you'd be changing the ABI to userspace which would now suddenly > return 0 instead of -ENODATA. Yeah let's avoid this if possible, even though I liked Tudor's approach. Would Michael proposal of checking it in mtd_otp_size() still affect userspace? If not, having a single check over the -ENODATA return code seems attractive. Thanks, Miquèl