From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754207AbcGSP7S (ORCPT ); Tue, 19 Jul 2016 11:59:18 -0400 Received: from down.free-electrons.com ([37.187.137.238]:52055 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753430AbcGSP7O (ORCPT ); Tue, 19 Jul 2016 11:59:14 -0400 Date: Tue, 19 Jul 2016 17:59:12 +0200 From: Boris Brezillon To: Richard Weinberger Cc: Andrey Smirnov , linux-mtd@lists.infradead.org, David Woodhouse , Brian Norris , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mtd: nand: BUG_ON in case of no select_chip and cmd_ctrl Message-ID: <20160719175912.11277116@bbrezillon> In-Reply-To: <578E4AF0.7090507@nod.at> References: <1468942904-26464-1-git-send-email-andrew.smirnov@gmail.com> <578E4AF0.7090507@nod.at> Organization: Free Electrons X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 19 Jul 2016 17:44:48 +0200 Richard Weinberger wrote: > Am 19.07.2016 um 17:41 schrieb Andrey Smirnov: > > If no user specified chip->select_chip() function is provided, code in > > nand_base.c will automatically set this hook to nand_select_chip(), > > which in turn depends on chip->cmd_ctrl() hook being valid. Not > > providing both of those functions in NAND controller driver (for example > > by mistake) will result in a bit cryptic segfault. Replace it with > > explicit BUG_ON statement so it would be obvious what went wrong. > > > > Signed-off-by: Andrey Smirnov > > --- > > drivers/mtd/nand/nand_base.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c > > index ce7b2ca..57043a6 100644 > > --- a/drivers/mtd/nand/nand_base.c > > +++ b/drivers/mtd/nand/nand_base.c > > @@ -3128,8 +3128,10 @@ static void nand_set_defaults(struct nand_chip *chip, int busw) > > if (chip->waitfunc == NULL) > > chip->waitfunc = nand_wait; > > > > - if (!chip->select_chip) > > + if (!chip->select_chip) { > > + BUG_ON(!chip->cmd_ctrl); > > Please don't add new BUG_ON() calls. WARN_ON() is good enough to raise the driver developer's > attention and won't kill the machine. Not sure a BUG_ON() is worst than a NULL-pointer exception ;-).