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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 A3A48C433F4 for ; Mon, 27 Aug 2018 07:23:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6022F2152E for ; Mon, 27 Aug 2018 07:23:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6022F2152E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bootlin.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727193AbeH0LJS (ORCPT ); Mon, 27 Aug 2018 07:09:18 -0400 Received: from mail.bootlin.com ([62.4.15.54]:58284 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726882AbeH0LJS (ORCPT ); Mon, 27 Aug 2018 07:09:18 -0400 Received: by mail.bootlin.com (Postfix, from userid 110) id 5C99120795; Mon, 27 Aug 2018 09:23:53 +0200 (CEST) Received: from bbrezillon (AAubervilliers-681-1-53-19.w90-88.abo.wanadoo.fr [90.88.170.19]) by mail.bootlin.com (Postfix) with ESMTPSA id 1CCD2206DE; Mon, 27 Aug 2018 09:23:43 +0200 (CEST) Date: Mon, 27 Aug 2018 09:23:41 +0200 From: Boris Brezillon To: Masahiro Yamada Cc: linux-mtd@lists.infradead.org, Miquel Raynal , linux-kernel@vger.kernel.org, Marek Vasut , Brian Norris , Richard Weinberger , David Woodhouse Subject: Re: [PATCH v2] mtd: rawnand: denali: do not pass zero maxchips to nand_scan() Message-ID: <20180827092341.1385ea7d@bbrezillon> In-Reply-To: <1535353301-1727-1-git-send-email-yamada.masahiro@socionext.com> References: <1535353301-1727-1-git-send-email-yamada.masahiro@socionext.com> X-Mailer: Claws Mail 3.15.0-dirty (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 27 Aug 2018 16:01:41 +0900 Masahiro Yamada wrote: > Commit 49aa76b16676 ("mtd: rawnand: do not execute nand_scan_ident() > if maxchips is zero") gave a new meaning for calling nand_scan_ident() > with maxchips=0. > > It is a special usage for some drivers such as docg4, but actually > the Denali driver may pass maxchips=0 to nand_scan() when the driver > is enabled but no NAND chip is found on the board for some reasons. > > If nand_scan_with_ids() is called with maxchips=0, nand_scan_ident() > is skipped, then nand_set_defaults() is skipped as well. Thus, the > driver must set chip->controller beforehand. Otherwise, nand_attach() > causes NULL pointer dereference. > > In fact, the Denali controller knows the number of connected chips > before calling nand_scan_ident(); if DEVICE_RESET fails, there is no > chip in that chip select. Then, denali_reset_banks() sets the maxchips > to the number of detected chips. If no chip is found, maxchips is zero. > > In this case, there is no point for calling nand_scan() because we know > it will fail for sure. Let's make the probe function fail immediately. > > Signed-off-by: Masahiro Yamada Looks good to me. I'm waiting for Miquel's ack and I'll queue it to mtd/fixes. Thanks, Boris