From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754875AbeCGXjC (ORCPT ); Wed, 7 Mar 2018 18:39:02 -0500 Received: from gateway34.websitewelcome.com ([192.185.150.107]:15050 "EHLO gateway34.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754642AbeCGXjB (ORCPT ); Wed, 7 Mar 2018 18:39:01 -0500 Subject: Re: [PATCH] rtc: remove VLA usage To: Alexandre Belloni Cc: "Gustavo A. R. Silva" , Alessandro Zummo , linux-rtc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20180307201133.GA5860@embeddedgus> <20180307212506.GO3035@piout.net> <3e8e1515-0f0e-73d4-72eb-3a2a2fbf04e9@embeddedor.com> <20180307230136.GB20370@piout.net> <20180307231258.GC20370@piout.net> From: "Gustavo A. R. Silva" Message-ID: Date: Wed, 7 Mar 2018 17:14:02 -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: <20180307231258.GC20370@piout.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit 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: 1etiG3-001JcX-WE 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]:39586 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 On 03/07/2018 05:12 PM, Alexandre Belloni wrote: > On 07/03/2018 at 17:09:22 -0600, Gustavo A. R. Silva wrote: >> >> On 03/07/2018 05:01 PM, Alexandre Belloni wrote: >>> On 07/03/2018 at 16:39:51 -0600, Gustavo A. R. Silva wrote: >>>> 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]; >>>> >>> Seems better, yes. >>> >>>>>> 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? >>>> >>> Nope, that RTC has a section of 255 bytes that could be read at once so >>> 257 is the correct value. >>> >> I see... >> >> I was looking into this piece of code drivers/rtc/rtc-mcp795.c:302: >> >>         tmp[0] = (tmp[0] & 0x80) | bin2bcd(alm->time.tm_sec); >>         tmp[1] = (tmp[1] & 0x80) | bin2bcd(alm->time.tm_min); >>         tmp[2] = (tmp[2] & 0xE0) | bin2bcd(alm->time.tm_hour); >>         tmp[3] = (tmp[3] & 0x80) | bin2bcd(alm->time.tm_wday + 1); >>         /* set alarm match: seconds, minutes, hour, day, date and month */ >>         tmp[3] |= (MCP795_ALM0C2_BIT | MCP795_ALM0C1_BIT | >> MCP795_ALM0C0_BIT); >>         tmp[4] = (tmp[4] & 0xC0) | bin2bcd(alm->time.tm_mday); >>         tmp[5] = (tmp[5] & 0xE0) | bin2bcd(alm->time.tm_mon + 1); >> >>         ret = mcp795_rtcc_write(dev, MCP795_REG_ALM0_SECONDS, tmp, >> sizeof(tmp)); >> > Yeah, the 128 or 255 bytes NVRAM is not yet supported but this is on my > todo list > I got it. Thanks -- Gustavo