[PATCH] usb: misc: cytherm: replace deprecated simple_strtoul with kstrtoint

[PATCH] usb: misc: cytherm: replace deprecated simple_strtoul with kstrtoint

[Jad Keskes]

simple_strtoul() is deprecated in favor of kstrtoint(). The old
function silently accepts garbage input. kstrtoint() returns -EINVAL
so the driver can actually tell the user they typed something stupid
instead of accepting 0 and wondering why the thermometer isn't
responding.

The 0-255 clamping stays the same, just with proper error handling
in front of it now.

Signed-off-by: Jad Keskes <inasj268@gmail.com>
---
 drivers/usb/misc/cytherm.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/misc/cytherm.c b/drivers/usb/misc/cytherm.c
index b183df9826bc..81de3fecf3da 100644
--- a/drivers/usb/misc/cytherm.c
+++ b/drivers/usb/misc/cytherm.c
@@ -85,7 +85,9 @@ static ssize_t brightness_store(struct device *dev, struct device_attribute *att
 	if (!buffer)
 		return 0;
 
-	cytherm->brightness = simple_strtoul(buf, NULL, 10);
+	retval = kstrtoint(buf, 10, &cytherm->brightness);
+	if (retval < 0)
+		return retval;
    
 	if (cytherm->brightness > 0xFF)
 		cytherm->brightness = 0xFF;
@@ -217,7 +219,9 @@ static ssize_t port0_store(struct device *dev, struct device_attribute *attr, co
 	if (!buffer)
 		return 0;
 
-	tmp = simple_strtoul(buf, NULL, 10);
+	retval = kstrtoint(buf, 10, &tmp);
+	if (retval < 0)
+		return retval;
    
 	if (tmp > 0xFF)
 		tmp = 0xFF;
@@ -272,7 +276,9 @@ static ssize_t port1_store(struct device *dev, struct device_attribute *attr, co
 	if (!buffer)
 		return 0;
 
-	tmp = simple_strtoul(buf, NULL, 10);
+	retval = kstrtoint(buf, 10, &tmp);
+	if (retval < 0)
+		return retval;
    
 	if (tmp > 0xFF)
 		tmp = 0xFF;
-- 
2.54.0

Re: [PATCH] usb: misc: cytherm: replace deprecated simple_strtoul with kstrtoint

[Greg KH]

On Mon, Jun 22, 2026 at 01:31:24PM +0100, Jad Keskes wrote:
> simple_strtoul() is deprecated in favor of kstrtoint(). The old
> function silently accepts garbage input. kstrtoint() returns -EINVAL
> so the driver can actually tell the user they typed something stupid
> instead of accepting 0 and wondering why the thermometer isn't
> responding.
> 
> The 0-255 clamping stays the same, just with proper error handling
> in front of it now.
> 
> Signed-off-by: Jad Keskes <inasj268@gmail.com>
> ---
>  drivers/usb/misc/cytherm.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/misc/cytherm.c b/drivers/usb/misc/cytherm.c
> index b183df9826bc..81de3fecf3da 100644
> --- a/drivers/usb/misc/cytherm.c
> +++ b/drivers/usb/misc/cytherm.c
> @@ -85,7 +85,9 @@ static ssize_t brightness_store(struct device *dev, struct device_attribute *att
>  	if (!buffer)
>  		return 0;
>  
> -	cytherm->brightness = simple_strtoul(buf, NULL, 10);
> +	retval = kstrtoint(buf, 10, &cytherm->brightness);
> +	if (retval < 0)
> +		return retval;

This changes the user/kernel functionality, are you sure it is safe to
do so?

What is wrong with leaving the current calls?

thanks,

greg k-h

Re: [PATCH] usb: misc: cytherm: replace deprecated simple_strtoul with kstrtoint

[Jad Keskes]

On 07/08, Greg KH wrote:
> This changes the user/kernel functionality, are you sure it is safe to
> do so?

Nobody writes garbage to these on purpose, and if they do by accident
they should get an error, not 0.  The only way this breaks is if some
tool depends on "echo foo > brightness" silently setting to 0 — which
would be a bug in that tool.

> What is wrong with leaving the current calls?

simple_strtoul is deprecated per deprecated.rst.  It ignores overflows
too — writing -1 wraps to ULONG_MAX then gets clamped to 0xFF instead
of erroring out.  kstrtoint returns -EINVAL for both.

Re: [PATCH] usb: misc: cytherm: replace deprecated simple_strtoul with kstrtoint

[Greg KH]

On Wed, Jul 08, 2026 at 04:20:03PM +0100, Jad Keskes wrote:
> On 07/08, Greg KH wrote:
> > This changes the user/kernel functionality, are you sure it is safe to
> > do so?
> 
> Nobody writes garbage to these on purpose, and if they do by accident
> they should get an error, not 0.  The only way this breaks is if some
> tool depends on "echo foo > brightness" silently setting to 0 — which
> would be a bug in that tool.
> 
> > What is wrong with leaving the current calls?
> 
> simple_strtoul is deprecated per deprecated.rst.  It ignores overflows
> too — writing -1 wraps to ULONG_MAX then gets clamped to 0xFF instead
> of erroring out.  kstrtoint returns -EINVAL for both.

Sure, it's deprecated, so don't add it to new code, but for existing
stuff, don't change how user/kernel interactions might work.

thanks,

greg k-h