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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 C5892C2B9F7 for ; Wed, 26 May 2021 10:41:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A23B7613C3 for ; Wed, 26 May 2021 10:41:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234104AbhEZKnK (ORCPT ); Wed, 26 May 2021 06:43:10 -0400 Received: from ssl.serverraum.org ([176.9.125.105]:40833 "EHLO ssl.serverraum.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233944AbhEZKnJ (ORCPT ); Wed, 26 May 2021 06:43:09 -0400 Received: from ssl.serverraum.org (web.serverraum.org [172.16.0.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ssl.serverraum.org (Postfix) with ESMTPSA id C4C7422236; Wed, 26 May 2021 12:41:36 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1622025697; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ErwKEEinBftiXZT6dwCMASUMXD5Y2QAmtSkdKSxxN08=; b=ZhmjZvPFhlGK54bGH1oN+oddaIB/Cw85IIej2dmgiSSSlv1lSNtQh4WqoY0uPbDOMFfKfd onaNwNAGtRJDm45Oqyue4xROpZlR8xJ4GnhvdFsTiBXo0DRIl+9ECvkQM0IxQ7a3t/+Rpr SDmLczovZLTQSgELeFfsbXTPHrNvhaA= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Wed, 26 May 2021 12:41:36 +0200 From: Michael Walle To: Pratyush Yadav Cc: linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, Tudor Ambarus , Miquel Raynal , Richard Weinberger , Vignesh Raghavendra Subject: Re: [PATCH v4 3/4] mtd: spi-nor: otp: return -EROFS if region is read-only In-Reply-To: <20210525193323.xdvbq3tab6oxk6yh@ti.com> References: <20210521194034.15249-1-michael@walle.cc> <20210521194034.15249-4-michael@walle.cc> <20210525193323.xdvbq3tab6oxk6yh@ti.com> User-Agent: Roundcube Webmail/1.4.11 Message-ID: X-Sender: michael@walle.cc Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 2021-05-25 21:33, schrieb Pratyush Yadav: > On 21/05/21 09:40PM, Michael Walle wrote: >> SPI NOR flashes will just ignore program commands if the OTP region is >> locked. Thus, a user might not notice that the intended write didn't >> end >> up in the flash. Return -EROFS to the user in this case. From what I >> can >> tell, chips/cfi_cmdset_0001.c also return this error code. >> >> One could optimize spi_nor_mtd_otp_range_is_locked() to read the >> status >> register only once and not for every OTP region, but for that we would >> need some more invasive changes. Given that this is >> one-time-programmable memory and the normal access mode is reading, we >> just live with the small overhead. > > Ok. > >> >> Fixes: 069089acf88b ("mtd: spi-nor: add OTP support") >> Signed-off-by: Michael Walle >> --- >> drivers/mtd/spi-nor/otp.c | 35 +++++++++++++++++++++++++++++++++++ >> 1 file changed, 35 insertions(+) >> >> diff --git a/drivers/mtd/spi-nor/otp.c b/drivers/mtd/spi-nor/otp.c >> index 3898ed67ba1c..b87f96593c13 100644 >> --- a/drivers/mtd/spi-nor/otp.c >> +++ b/drivers/mtd/spi-nor/otp.c >> @@ -249,6 +249,31 @@ static int spi_nor_mtd_otp_info(struct mtd_info >> *mtd, size_t len, >> return ret; >> } >> >> +static int spi_nor_mtd_otp_range_is_locked(struct spi_nor *nor, >> loff_t ofs, >> + size_t len) >> +{ >> + const struct spi_nor_otp_ops *ops = nor->params->otp.ops; >> + unsigned int region; >> + int locked; >> + >> + if (!len) >> + return 0; > > I was inclined to say that the loop conditional below would take care > of > this but it can cause an underflow when ofs and len are both 0. Correct. I didn't want to put an extra check to the caller, because as you noticed, it is checked by the loop there later. >> + >> + /* >> + * If any of the affected OTP regions are locked the entire range is >> + * considered locked. >> + */ >> + for (region = spi_nor_otp_offset_to_region(nor, ofs); >> + region <= spi_nor_otp_offset_to_region(nor, ofs + len - 1); >> + region++) { >> + locked = ops->is_locked(nor, region); >> + if (locked) >> + return locked; >> + } > > Ok. Btw I didn't know if I should put a comment here that this if () handles both locked state and errors. But it seems you've already found out by looking at the caller ;) I'm not sure if this is obvious, though. >> + >> + return 0; >> +} >> + >> static int spi_nor_mtd_otp_read_write(struct mtd_info *mtd, loff_t >> ofs, >> size_t total_len, size_t *retlen, >> const u8 *buf, bool is_write) >> @@ -271,6 +296,16 @@ static int spi_nor_mtd_otp_read_write(struct >> mtd_info *mtd, loff_t ofs, >> /* don't access beyond the end */ >> total_len = min_t(size_t, total_len, spi_nor_otp_size(nor) - ofs); >> >> + if (is_write) { >> + ret = spi_nor_mtd_otp_range_is_locked(nor, ofs, total_len); >> + if (ret < 0) { >> + goto out; >> + } else if (ret) { >> + ret = -EROFS; > > I wonder if we should have a dev_info() or dev_err() here. I think this > warrants a dev_dbg() at least. Are you sure? Reporting something to the user via an error code is enough IMHO. I wouldn't want my syslog to be cluttered with messages I already know. I mean the program tell me "hey, you aren't allowed to write there". Why would the kernel still need to tell me that again? Without any connection to the caller, I don't get much out of the kernel message by looking at it alone, just that someone tried to write there. So definetly no dev_info() or dev_err(). But IMHO no dev_dbg() either. Tudor, Vingesh, any opinions? >> + goto out; >> + } > > So it returns -errno when the check for is_locked() fails and 1 or 0 > when it is locked or not. Ok. > > It would be nice if you add a dev_dbg or dev_err() or dev_info() above. > Nonetheless, > > Reviewed-by: Pratyush Yadav Thanks for reviewing! -michael