linux-kernel - Re: [PATCH] bus: mhi: core: replace snprintf with sysfs

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Date:   Wed, 8 Dec 2021 22:03:30 +0800
From:   Yihao Han <hanyihao@...o.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Manivannan Sadhasivam <mani@...nel.org>,
        Hemant Kumar <hemantk@...eaurora.org>,
        Bhaumik Bhatt <bbhatt@...eaurora.org>,
        Loic Poulain <loic.poulain@...aro.org>,
        Carl Yin <carl.yin@...ctel.com>,
        Carl Huang <cjhuang@...eaurora.org>, mhi@...ts.linux.dev,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...o.com
Subject: Re: [PATCH] bus: mhi: core: replace snprintf with sysfs_emit



On 2021/12/8 16:14, Greg Kroah-Hartman wrote:
> On Wed, Dec 08, 2021 at 12:07:53AM -0800, Yihao Han wrote:
>> coccinelle report:
>> ./drivers/bus/mhi/core/init.c:97:8-16:
>> WARNING: use scnprintf or sprintf
>> Use sysfs_emit instead of scnprintf or sprintf makes more sense.
>>
>> Signed-off-by: Yihao Han <hanyihao@...o.com>
>> ---
>>   drivers/bus/mhi/core/init.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
>> index 5aaca6d0f52b..a5a5c722731e 100644
>> --- a/drivers/bus/mhi/core/init.c
>> +++ b/drivers/bus/mhi/core/init.c
>> @@ -94,7 +94,7 @@ static ssize_t serial_number_show(struct device *dev,
>>   	struct mhi_device *mhi_dev = to_mhi_device(dev);
>>   	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
>>   
>> -	return snprintf(buf, PAGE_SIZE, "Serial Number: %u\n",
>> +	return sysfs_emit(buf, "Serial Number: %u\n",
>>   			mhi_cntrl->serial_number);
>>   }
>>   static DEVICE_ATTR_RO(serial_number);
>> -- 
>> 2.17.1
>>
> 
> Why are you only changing one function in this file?  If you realyl want
> to make a change like this, fix ALL sysfs show functions.
> 
> thanks,
> 
> greg k-h
Because "sysfs_emit()" is "scnprintf()" equivalent with "size" parameter 
equals to PAGE_SIZE,So sysfs_emit can only be used here in this file. 
And "scnprintf" is better than "snprintf" because the former returns 
number of characters written to "buf". So I think we can use 
"sysfs_emit()" instead of "snprintf()".

Thanks,
Yihao