linux-kernel - Re: [PATCH 1/7] comedi: Convert snprintf() to scnprintf()

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Date:   Wed, 28 Sep 2022 16:45:53 +0100
From:   Ian Abbott <abbotti@....co.uk>
To:     Greg KH <gregkh@...uxfoundation.org>,
        Jules Irenge <jbi.octave@...il.com>
Cc:     hsweeten@...ionengravers.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] comedi: Convert snprintf() to scnprintf()

On 27/09/2022 07:06, Greg KH wrote:
> On Mon, Sep 26, 2022 at 07:37:37PM +0100, Jules Irenge wrote:
>> Coccinnelle reports a warning
>> Warning: Use scnprintf or sprintf
>> Adding to that, there has been a slow migration from snprintf to scnprintf.
>> This LWN article explains the rationale for this change
>> https: //lwn.net/Articles/69419/
>> Ie. snprintf() returns what *would* be the resulting length,
>> while scnprintf() returns the actual length.
>>
>> Signed-off-by: Jules Irenge <jbi.octave@...il.com>
>> ---
>>   drivers/comedi/comedi_fops.c | 8 ++++----
>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/comedi/comedi_fops.c b/drivers/comedi/comedi_fops.c
>> index 55a0cae04b8d..e8a0142d5894 100644
>> --- a/drivers/comedi/comedi_fops.c
>> +++ b/drivers/comedi/comedi_fops.c
>> @@ -396,7 +396,7 @@ static ssize_t max_read_buffer_kb_show(struct device *csdev,
>>   	mutex_unlock(&dev->mutex);
>>   
>>   	comedi_dev_put(dev);
>> -	return snprintf(buf, PAGE_SIZE, "%u\n", size);
>> +	return scnprintf(buf, PAGE_SIZE, "%u\n", size);
> 
> Ick, no, you should use sysfs_emit() if you really want to change these
> functions to "do the right thing".

There was a patch to do that by Xuezhi Zhang.  It got to PATCH v4.  I 
should have replied with a "Reviewed-By" tag, but I'd already done that 
for the earlier versions.

https://lore.kernel.org/lkml/20220901013423.418464-1-zhangxuezhi3@gmail.com/

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