[PATCH] sisfb: Replace creative use of the ternary operator

[PATCH] sisfb: Replace creative use of the ternary operator

[Ben Hutchings]

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GETBITSTR() and related macros are defined in such a way that two of
the macro arguments must be pairs of integers joined with a ':',
selected between by prepending '1?' or '0?'.  This is rather clever
but not very readable.  Redefine the macros and change the users so
that each integer is a separate argument.

While we're at it, add a BUILD_BUG_ON_ZERO() to check that the
redundant first part of the 'to' argument is consistent with the
other arguments.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/video/fbdev/sis/init.c | 32 +++++++++++++++-----------------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/drivers/video/fbdev/sis/init.c b/drivers/video/fbdev/sis/init.c
index dfe3eb7..d0c2e72 100644
--- a/drivers/video/fbdev/sis/init.c
+++ b/drivers/video/fbdev/sis/init.c
@@ -3320,11 +3320,9 @@ SiSSetMode(struct SiS_Private *SiS_Pr, unsigned short ModeNo)
    return true;
 }
 
-#ifndef GETBITSTR
-#define GENBITSMASK(mask)   	GENMASK(1?mask,0?mask)
-#define GETBITS(var,mask)   	(((var) & GENBITSMASK(mask)) >> (0?mask))
-#define GETBITSTR(val,from,to)  ((GETBITS(val,from)) << (0?to))
-#endif
+#define GETBITSTR(val, fromhigh, fromlow, tohigh, tolow)		    \
+	(((((val) & GENMASK(fromhigh, fromlow)) >> (fromlow)) << (tolow)) + \
+	 BUILD_BUG_ON_ZERO((fromhigh) - (fromlow) != (tohigh) - (tolow)))
 
 void
 SiS_CalcCRRegisters(struct SiS_Private *SiS_Pr, int depth)
@@ -3363,23 +3361,23 @@ SiS_CalcCRRegisters(struct SiS_Private *SiS_Pr, int depth)
    SiS_Pr->CCRT1CRTC[12] = (SiS_Pr->CVBlankEnd   - 1) & 0xFF;			/* CR16 */
 
    SiS_Pr->CCRT1CRTC[13] =							/* SRA */
-			GETBITSTR((SiS_Pr->CVTotal     -2), 10:10, 0:0) |
-			GETBITSTR((SiS_Pr->CVDisplay   -1), 10:10, 1:1) |
-			GETBITSTR((SiS_Pr->CVBlankStart-1), 10:10, 2:2) |
-			GETBITSTR((SiS_Pr->CVSyncStart -x), 10:10, 3:3) |
-			GETBITSTR((SiS_Pr->CVBlankEnd  -1),   8:8, 4:4) |
-			GETBITSTR((SiS_Pr->CVSyncEnd     ),   4:4, 5:5) ;
+			GETBITSTR((SiS_Pr->CVTotal     -2), 10, 10, 0, 0) |
+			GETBITSTR((SiS_Pr->CVDisplay   -1), 10, 10, 1, 1) |
+			GETBITSTR((SiS_Pr->CVBlankStart-1), 10, 10, 2, 2) |
+			GETBITSTR((SiS_Pr->CVSyncStart -x), 10, 10, 3, 3) |
+			GETBITSTR((SiS_Pr->CVBlankEnd  -1),  8,  8, 4, 4) |
+			GETBITSTR((SiS_Pr->CVSyncEnd     ),  4,  4, 5, 5) ;
 
    SiS_Pr->CCRT1CRTC[14] =							/* SRB */
-			GETBITSTR((SiS_Pr->CHTotal      >> 3) - 5, 9:8, 1:0) |
-			GETBITSTR((SiS_Pr->CHDisplay    >> 3) - 1, 9:8, 3:2) |
-			GETBITSTR((SiS_Pr->CHBlankStart >> 3) - 1, 9:8, 5:4) |
-			GETBITSTR((SiS_Pr->CHSyncStart  >> 3) + 3, 9:8, 7:6) ;
+			GETBITSTR((SiS_Pr->CHTotal      >> 3) - 5, 9, 8, 1, 0) |
+			GETBITSTR((SiS_Pr->CHDisplay    >> 3) - 1, 9, 8, 3, 2) |
+			GETBITSTR((SiS_Pr->CHBlankStart >> 3) - 1, 9, 8, 5, 4) |
+			GETBITSTR((SiS_Pr->CHSyncStart  >> 3) + 3, 9, 8, 7, 6) ;
 

    SiS_Pr->CCRT1CRTC[15] =							/* SRC */
-			GETBITSTR((SiS_Pr->CHBlankEnd >> 3) - 1, 7:6, 1:0) |
-			GETBITSTR((SiS_Pr->CHSyncEnd  >> 3) + 3, 5:5, 2:2) ;
+			GETBITSTR((SiS_Pr->CHBlankEnd >> 3) - 1, 7, 6, 1, 0) |
+			GETBITSTR((SiS_Pr->CHSyncEnd  >> 3) + 3, 5, 5, 2, 2) ;
 }
 
 void

-- 
Ben Hutchings
Sturgeon's Law: Ninety percent of everything is crap.

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