From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934303AbeCGWkN (ORCPT ); Wed, 7 Mar 2018 17:40:13 -0500 Received: from gateway23.websitewelcome.com ([192.185.49.219]:39046 "EHLO gateway23.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934240AbeCGWkM (ORCPT ); Wed, 7 Mar 2018 17:40:12 -0500 Subject: Re: [PATCH] rtc: remove VLA usage To: Alexandre Belloni , "Gustavo A. R. Silva" Cc: Alessandro Zummo , linux-rtc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20180307201133.GA5860@embeddedgus> <20180307212506.GO3035@piout.net> From: "Gustavo A. R. Silva" Message-ID: <4b85f83a-cbf7-ffe7-ec92-03aeb7fbd958@embeddedor.com> Date: Wed, 7 Mar 2018 16:40:05 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180307212506.GO3035@piout.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 187.162.24.133 X-Source-L: No X-Exim-ID: 1ethjF-000kL3-Tm X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: 187-162-24-133.static.axtel.net ([192.168.3.98]) [187.162.24.133]:18934 X-Source-Auth: garsilva@embeddedor.com X-Email-Count: 8 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Alexandre, On 03/07/2018 03:25 PM, Alexandre Belloni wrote: > On 07/03/2018 at 14:11:33 -0600, Gustavo A. R. Silva wrote: >> In preparation to enabling -Wvla, remove VLA and replace it >> with a fixed-length array instead. >> > You should probably explain what VLA is and why this is important to do. Sure. I can elaborate a little bit more. >> Signed-off-by: Gustavo A. R. Silva >> --- >> drivers/rtc/rtc-bq32k.c | 2 +- >> drivers/rtc/rtc-mcp795.c | 2 +- >> 2 files changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/rtc/rtc-bq32k.c b/drivers/rtc/rtc-bq32k.c >> index e8698e9..e4b234a 100644 >> --- a/drivers/rtc/rtc-bq32k.c >> +++ b/drivers/rtc/rtc-bq32k.c >> @@ -74,7 +74,7 @@ static int bq32k_read(struct device *dev, void *data, uint8_t off, uint8_t len) >> static int bq32k_write(struct device *dev, void *data, uint8_t off, uint8_t len) >> { >> struct i2c_client *client = to_i2c_client(dev); >> - uint8_t buffer[len + 1]; >> + uint8_t buffer[256]; >> > You chose to change len to 255, probably because this is a uint8_t but Correct. > this is way too much for this rtc, it only has 10 consecutive registers. In that case probably the best solution is to add the following line to the module: #define MAX_LEN 10 and update the rest of the code as follows: uint8_t buffer[MAX_LEN + 1]; >> buffer[0] = off; >> memcpy(&buffer[1], data, len); >> diff --git a/drivers/rtc/rtc-mcp795.c b/drivers/rtc/rtc-mcp795.c >> index 79e24ea..00e11c1 100644 >> --- a/drivers/rtc/rtc-mcp795.c >> +++ b/drivers/rtc/rtc-mcp795.c >> @@ -82,7 +82,7 @@ static int mcp795_rtcc_write(struct device *dev, u8 addr, u8 *data, u8 count) >> { >> struct spi_device *spi = to_spi_device(dev); >> int ret; >> - u8 tx[2 + count]; >> + u8 tx[257]; For this particular case it seems to me that the following works just fine: #define MAX_COUNT 7 u8 tx[MAX_COUNT + 2]; What do you think? Thanks for your feedback. -- Gustavo >> >> tx[0] = MCP795_WRITE; >> tx[1] = addr; >> -- >> 2.7.4 >>