RE: [PATCH v4 1/1] drm/i915: Move abs_diff() to math.h

2023-08-04 Thread David Laight 
From: Andrew Morton
> Sent: 03 August 2023 18:25
> 
> On Thu,  3 Aug 2023 16:19:18 +0300 Andy Shevchenko 
>  wrote:
> 
> > abs_diff() belongs to math.h. Move it there.
> > This will allow others to use it.
> >
> > ...
> >
> > --- a/include/linux/math.h
> > +++ b/include/linux/math.h
> > @@ -155,6 +155,13 @@ __STRUCT_FRACT(u32)
> > __builtin_types_compatible_p(typeof(x), unsigned type), \
> > ({ signed type __x = (x); __x < 0 ? -__x : __x; }), other)
> >
> > +#define abs_diff(a, b) ({  \
> > +   typeof(a) __a = (a);\
> > +   typeof(b) __b = (b);\
> > +   (void)(&__a == &__b);   \
> > +   __a > __b ? (__a - __b) : (__b - __a);  \
> > +})
> 
> Can we document it please?
> 
> Also, the open-coded type comparison could be replaced with __typecheck()?
> 
> And why the heck isn't __typecheck() in typecheck.h, to be included by
> minmax.h.

And why would you want to use __typecheck() anyway?
It pretty much isn't the test you are looking for.
If you are trying to explicitly avoid converting negative value
to large positive unsigned ones then you want something like:
is_signed_type(typeof(a)) == is_signed_type(typeof(b))
but it isn't even that simple :-)

David

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

Re: [PATCH v4 1/1] drm/i915: Move abs_diff() to math.h

2023-08-03 Thread Andy Shevchenko 
On Thu, Aug 03, 2023 at 10:24:46AM -0700, Andrew Morton wrote:
> On Thu,  3 Aug 2023 16:19:18 +0300 Andy Shevchenko 
>  wrote:

...

> > +#define abs_diff(a, b) ({  \
> > +   typeof(a) __a = (a);\
> > +   typeof(b) __b = (b);\
> > +   (void)(&__a == &__b);   \
> > +   __a > __b ? (__a - __b) : (__b - __a);  \
> > +})
> 
> Can we document it please?
> 
> Also, the open-coded type comparison could be replaced with __typecheck()?
> 
> And why the heck isn't __typecheck() in typecheck.h, to be included by
> minmax.h.
> 
> etcetera.  Sigh.  I'll grab it, but please at least send along some
> kerneldoc?

Sure and thank you!

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v4 1/1] drm/i915: Move abs_diff() to math.h

2023-08-03 Thread Andrew Morton 
On Thu,  3 Aug 2023 16:19:18 +0300 Andy Shevchenko 
 wrote:

> abs_diff() belongs to math.h. Move it there.
> This will allow others to use it.
> 
> ...
>
> --- a/include/linux/math.h
> +++ b/include/linux/math.h
> @@ -155,6 +155,13 @@ __STRUCT_FRACT(u32)
>   __builtin_types_compatible_p(typeof(x), unsigned type), \
>   ({ signed type __x = (x); __x < 0 ? -__x : __x; }), other)
>  
> +#define abs_diff(a, b) ({\
> + typeof(a) __a = (a);\
> + typeof(b) __b = (b);\
> + (void)(&__a == &__b);   \
> + __a > __b ? (__a - __b) : (__b - __a);  \
> +})

Can we document it please?

Also, the open-coded type comparison could be replaced with __typecheck()?

And why the heck isn't __typecheck() in typecheck.h, to be included by
minmax.h.

etcetera.  Sigh.  I'll grab it, but please at least send along some
kerneldoc?

[PATCH v4 1/1] drm/i915: Move abs_diff() to math.h

2023-08-03 Thread Andy Shevchenko 
abs_diff() belongs to math.h. Move it there.
This will allow others to use it.

Reviewed-by: Jiri Slaby  # tty/serial
Acked-by: Jani Nikula 
Acked-by: Greg Kroah-Hartman 
Reviewed-by: Andi Shyti 
Reviewed-by: Philipp Zabel  # gpu/ipu-v3
Signed-off-by: Andy Shevchenko 
---
v4:
- Cc'ed to Andrew (as Jani told he is okay to route it via other tree)
- added tags
 drivers/gpu/drm/i915/display/intel_dpll_mgr.c |  1 +
 drivers/gpu/drm/i915/display/intel_dpll_mgr.h |  7 ---
 drivers/gpu/ipu-v3/ipu-image-convert.c| 15 +++
 drivers/tty/serial/omap-serial.c  |  7 +--
 drivers/video/fbdev/core/svgalib.c|  7 +--
 include/linux/math.h  |  7 +++
 6 files changed, 17 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c 
b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
index 6b2d8a1e2aa9..290e856fe9e9 100644
--- a/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
+++ b/drivers/gpu/drm/i915/display/intel_dpll_mgr.c
@@ -21,6 +21,7 @@
  * DEALINGS IN THE SOFTWARE.
  */
 
+#include 
 #include 
 
 #include "i915_reg.h"
diff --git a/drivers/gpu/drm/i915/display/intel_dpll_mgr.h 
b/drivers/gpu/drm/i915/display/intel_dpll_mgr.h
index ba62eb5d7c51..04e6810954b2 100644
--- a/drivers/gpu/drm/i915/display/intel_dpll_mgr.h
+++ b/drivers/gpu/drm/i915/display/intel_dpll_mgr.h
@@ -29,13 +29,6 @@
 
 #include "intel_wakeref.h"
 
-/*FIXME: Move this to a more appropriate place. */
-#define abs_diff(a, b) ({  \
-   typeof(a) __a = (a);\
-   typeof(b) __b = (b);\
-   (void) (&__a == &__b);  \
-   __a > __b ? (__a - __b) : (__b - __a); })
-
 enum tc_port;
 struct drm_i915_private;
 struct intel_atomic_state;
diff --git a/drivers/gpu/ipu-v3/ipu-image-convert.c 
b/drivers/gpu/ipu-v3/ipu-image-convert.c
index af1612044eef..841316582ea9 100644
--- a/drivers/gpu/ipu-v3/ipu-image-convert.c
+++ b/drivers/gpu/ipu-v3/ipu-image-convert.c
@@ -7,7 +7,10 @@
 
 #include 
 #include 
+#include 
+
 #include 
+
 #include "ipu-prv.h"
 
 /*
@@ -543,7 +546,7 @@ static void find_best_seam(struct ipu_image_convert_ctx 
*ctx,
unsigned int in_pos;
unsigned int in_pos_aligned;
unsigned int in_pos_rounded;
-   unsigned int abs_diff;
+   unsigned int diff;
 
/*
 * Tiles in the right row / bottom column may not be allowed to
@@ -575,15 +578,11 @@ static void find_best_seam(struct ipu_image_convert_ctx 
*ctx,
(in_edge - in_pos_rounded) % in_burst)
continue;
 
-   if (in_pos < in_pos_aligned)
-   abs_diff = in_pos_aligned - in_pos;
-   else
-   abs_diff = in_pos - in_pos_aligned;
-
-   if (abs_diff < min_diff) {
+   diff = abs_diff(in_pos, in_pos_aligned);
+   if (diff < min_diff) {
in_seam = in_pos_rounded;
out_seam = out_pos;
-   min_diff = abs_diff;
+   min_diff = diff;
}
}
 
diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index 3dc14dcb01ca..0ead88c5a19a 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -222,16 +222,11 @@ static inline int calculate_baud_abs_diff(struct 
uart_port *port,
unsigned int baud, unsigned int mode)
 {
unsigned int n = port->uartclk / (mode * baud);
-   int abs_diff;
 
if (n == 0)
n = 1;
 
-   abs_diff = baud - (port->uartclk / (mode * n));
-   if (abs_diff < 0)
-   abs_diff = -abs_diff;
-
-   return abs_diff;
+   return abs_diff(baud, port->uartclk / (mode * n));
 }
 
 /*
diff --git a/drivers/video/fbdev/core/svgalib.c 
b/drivers/video/fbdev/core/svgalib.c
index 9e01322fabe3..2cba15ea 100644
--- a/drivers/video/fbdev/core/svgalib.c
+++ b/drivers/video/fbdev/core/svgalib.c
@@ -14,6 +14,7 @@
 #include 
 #include 
 #include 
+#include 
 #include 
 #include 
 #include 
@@ -372,12 +373,6 @@ EXPORT_SYMBOL(svga_get_caps);
  *  F_VCO = (F_BASE * M) / N
  *  F_OUT = F_VCO / (2^R)
  */
-
-static inline u32 abs_diff(u32 a, u32 b)
-{
-   return (a > b) ? (a - b) : (b - a);
-}
-
 int svga_compute_pll(const struct svga_pll *pll, u32 f_wanted, u16 *m, u16 *n, 
u16 *r, int node)
 {
u16 am, an, ar;
diff --git a/include/linux/math.h b/include/linux/math.h
index 2d388650c556..336e3e3678e7 100644
--- a/include/linux/math.h
+++ b/include/linux/math.h
@@ -155,6 +155,13 @@ __STRUCT_FRACT(u32)
__builtin_types_compatible_p(typeof(x), unsigned type), \
({ signed type __x = (x); __x < 0 ? -__x : __x; }), other)
 
+#define abs_diff(a, b) ({  \
+   typeof(a) __a = (a);