From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.bootlin.com ([62.4.15.54]:59950 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751362AbeCLXbI (ORCPT ); Mon, 12 Mar 2018 19:31:08 -0400 Date: Tue, 13 Mar 2018 00:31:02 +0100 From: Alexandre Belloni To: Stefano Manni Cc: a.zummo@towertech.it, linux-rtc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] rtc: mcp795: remove VLA usage Message-ID: <20180312233102.GE3795@piout.net> References: <20180312231338.3756-1-stefano.manni@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20180312231338.3756-1-stefano.manni@gmail.com> Sender: linux-rtc-owner@vger.kernel.org List-ID: Hi, On 13/03/2018 at 00:13:38 +0100, Stefano Manni wrote: > In preparation to enabling -Wvla, remove VLAs and replace them with > fixed-length arrays instead. > > rtc-mcp795.c uses a variable-length array declaration to contain > the command to write the rtcc; this can be replaced by a fixed- > size array of length 2 (instruction, address) + 32 (data out), > assuming a maximum data length of 32 bytes before wrap up. > > This was prompted by https://lkml.org/lkml/2018/3/7/621 > > Signed-off-by: Stefano Manni > --- > drivers/rtc/rtc-mcp795.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/drivers/rtc/rtc-mcp795.c b/drivers/rtc/rtc-mcp795.c > index 77f21331ae21..a5f504e2364c 100644 > --- a/drivers/rtc/rtc-mcp795.c > +++ b/drivers/rtc/rtc-mcp795.c > @@ -61,6 +61,9 @@ > > #define SEC_PER_DAY (24 * 60 * 60) > > +/* Maximum length for data out in write operation to RTCC */ > +#define MCP795_MAX_DATAOUT_LEN 32 > + This is wrong, see https://marc.info/?l=linux-kernel&m=152046370320811&w=2 Also, https://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux.git/commit/?h=rtc-next&id=74ce1a932504da166cfbccf5567aa3751b6aa599 -- Alexandre Belloni, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com