[PATCH v1 1/1] pktcdvd: Use clamp_val() instead of min()+max()

[PATCH v1 1/1] pktcdvd: Use clamp_val() instead of min()+max()

[Andy Shevchenko]

In a couple of places replace min()+max() pair by clamp_val().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/block/pktcdvd.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index a1428538bda5..18a960bb6165 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -208,14 +208,11 @@ static DEVICE_ATTR_RO(size);
 static void init_write_congestion_marks(int* lo, int* hi)
 {
 	if (*hi > 0) {
-		*hi = max(*hi, 500);
-		*hi = min(*hi, 1000000);
+		*hi = clamp_val(*hi, 500, 1000000);
 		if (*lo <= 0)
 			*lo = *hi - 100;
-		else {
-			*lo = min(*lo, *hi - 100);
-			*lo = max(*lo, 100);
-		}
+		else
+			*lo = clamp_val(*lo, 100, *hi - 100);
 	} else {
 		*hi = -1;
 		*lo = -1;
-- 
2.40.0.1.gaa8946217a0b

RE: [PATCH v1 1/1] pktcdvd: Use clamp_val() instead of min()+max()

[David Laight]

From: Andy Shevchenko
> Sent: 16 June 2023 15:26
> 
> In a couple of places replace min()+max() pair by clamp_val().
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>  drivers/block/pktcdvd.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
> index a1428538bda5..18a960bb6165 100644
> --- a/drivers/block/pktcdvd.c
> +++ b/drivers/block/pktcdvd.c
> @@ -208,14 +208,11 @@ static DEVICE_ATTR_RO(size);
>  static void init_write_congestion_marks(int* lo, int* hi)
>  {
>  	if (*hi > 0) {
> -		*hi = max(*hi, 500);
> -		*hi = min(*hi, 1000000);
> +		*hi = clamp_val(*hi, 500, 1000000);

(standard rant about minmax.h)

clamp_val() is pretty much broken by design.
It MIGHT be ok here but it casts both limits to the
type of the value being compared.
In general that is just plain wrong.

Like min_t() it is generally ok because the kernel only uses
unsigned values between 0 and MAXINT.

If min/max were ok, then using clamp() should also be ok.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH v1 1/1] pktcdvd: Use clamp_val() instead of min()+max()

['Andy Shevchenko']

On Tue, Jun 20, 2023 at 12:06:49PM +0000, David Laight wrote:

...

> > +		*hi = clamp_val(*hi, 500, 1000000);
> 
> (standard rant about minmax.h)
> 
> clamp_val() is pretty much broken by design.
> It MIGHT be ok here but it casts both limits to the
> type of the value being compared.
> In general that is just plain wrong.
> 
> Like min_t() it is generally ok because the kernel only uses
> unsigned values between 0 and MAXINT.
> 
> If min/max were ok, then using clamp() should also be ok.

Submit a patch to fix it, if you think you can make it better.
Obviously your comment can be addressed separately if we even
need that.

-- 
With Best Regards,
Andy Shevchenko

RE: [PATCH v1 1/1] pktcdvd: Use clamp_val() instead of min()+max()

[David Laight]

From: 'Andy Shevchenko'
> Sent: 20 June 2023 14:25
> 
> On Tue, Jun 20, 2023 at 12:06:49PM +0000, David Laight wrote:
> 
> ...
> 
> > > +		*hi = clamp_val(*hi, 500, 1000000);
> >
> > (standard rant about minmax.h)
> >
> > clamp_val() is pretty much broken by design.
> > It MIGHT be ok here but it casts both limits to the
> > type of the value being compared.
> > In general that is just plain wrong.
> >
> > Like min_t() it is generally ok because the kernel only uses
> > unsigned values between 0 and MAXINT.
> >
> > If min/max were ok, then using clamp() should also be ok.
> 
> Submit a patch to fix it, if you think you can make it better.
> Obviously your comment can be addressed separately if we even
> need that.

Did you try using clamp() ?

To see why clamp_val() is broken consider?
	unsigned char val = 200;
	...
	xxx = clamp_val(val, 10, 300);
 
This sets xxx to 44 - not exactly expected.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH v1 1/1] pktcdvd: Use clamp_val() instead of min()+max()

['Andy Shevchenko']

On Tue, Jun 20, 2023 at 01:35:11PM +0000, David Laight wrote:
> From: 'Andy Shevchenko'
> > Sent: 20 June 2023 14:25
> > On Tue, Jun 20, 2023 at 12:06:49PM +0000, David Laight wrote:

...

> > > > +		*hi = clamp_val(*hi, 500, 1000000);
> > >
> > > (standard rant about minmax.h)
> > >
> > > clamp_val() is pretty much broken by design.
> > > It MIGHT be ok here but it casts both limits to the
> > > type of the value being compared.
> > > In general that is just plain wrong.
> > >
> > > Like min_t() it is generally ok because the kernel only uses
> > > unsigned values between 0 and MAXINT.
> > >
> > > If min/max were ok, then using clamp() should also be ok.
> > 
> > Submit a patch to fix it, if you think you can make it better.
> > Obviously your comment can be addressed separately if we even
> > need that.
> 
> Did you try using clamp() ?
> 
> To see why clamp_val() is broken consider?
> 	unsigned char val = 200;
> 	...
> 	xxx = clamp_val(val, 10, 300);
>  
> This sets xxx to 44 - not exactly expected.

Right, clamp_val() has to be improved.
However this is not the case in this driver.

I have just sent a v2 with clamp().

-- 
With Best Regards,
Andy Shevchenko