[PATCH 1/7] comedi: Convert snprintf() to scnprintf()

[PATCH 1/7] comedi: Convert snprintf() to scnprintf()

[Jules Irenge]

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@gmail.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);
 }
 
 static ssize_t max_read_buffer_kb_store(struct device *csdev,
@@ -452,7 +452,7 @@ static ssize_t 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);
 }
 
 static ssize_t read_buffer_kb_store(struct device *csdev,
@@ -509,7 +509,7 @@ static ssize_t max_write_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);
 }
 
 static ssize_t max_write_buffer_kb_store(struct device *csdev,
@@ -565,7 +565,7 @@ static ssize_t write_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);
 }
 
 static ssize_t write_buffer_kb_store(struct device *csdev,
-- 
2.37.3

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

[Greg KH]

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@gmail.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".

thanks,

greg k-h

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

[Jules Irenge]

On Tue, Sep 27, 2022 at 08:06:55AM +0200, 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@gmail.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".
> 
> thanks,
> 
> greg k-h

Thanks for feedback. 

I just sent a different version.

I will appreciate any more feedback.

Thanks,

Jules

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

[Ian Abbott]

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@gmail.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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-=( registered in England & Wales.  Regd. number: 02862268.  )=-
-=( Regd. addr.: S11 & 12 Building 67, Europa Business Park, )=-
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Re: [PATCH 1/7] comedi: Convert snprintf() to scnprintf()

[Jules Irenge]

On Wed, Sep 28, 2022 at 04:45:53PM +0100, Ian Abbott wrote:
> 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@gmail.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/
> 
Great, it's good to know how to fix the warning anyway.

Thanks,
Jules