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

abs_diff() belongs to math.h. Move it there.
This will allow others to use it.

Reviewed-by: Jiri Slaby <jirislaby@kernel.org> # tty/serial
Acked-by: Jani Nikula <redacted>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Andi Shyti <redacted>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de> # gpu/ipu-v3
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
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 <linux/math.h>
 #include <linux/string_helpers.h>
 
 #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 <linux/interrupt.h>
 #include <linux/dma-mapping.h>
+#include <linux/math.h>
+
 #include <video/imx-ipu-image-convert.h>
+
 #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..2cba158888ea 100644
--- a/drivers/video/fbdev/core/svgalib.c
+++ b/drivers/video/fbdev/core/svgalib.c

@@ -14,6 +14,7 @@
 #include <linux/kernel.h>
 #include <linux/string.h>
 #include <linux/fb.h>
+#include <linux/math.h>
 #include <linux/svga.h>
 #include <asm/types.h>
 #include <asm/io.h>

@@ -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);			\
+	typeof(b) __b = (b);			\
+	(void)(&__a == &__b);			\
+	__a > __b ? (__a - __b) : (__b - __a);	\
+})
+
 /**
  * reciprocal_scale - "scale" a value into range [0, ep_ro)
  * @val: value

-- 
2.40.0.1.gaa8946217a0b

On Thu,  3 Aug 2023 16:19:18 +0300 Andy Shevchenko [off-list ref] wrote:

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?

On Thu, Aug 03, 2023 at 10:24:46AM -0700, Andrew Morton wrote:

On Thu,  3 Aug 2023 16:19:18 +0300 Andy Shevchenko [off-list ref] wrote:

...

quoted

+#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

From: Andrew Morton

Sent: 03 August 2023 18:25

On Thu,  3 Aug 2023 16:19:18 +0300 Andy Shevchenko [off-list ref] wrote:

quoted

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

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