fbdev: c2p - Cleanups

  - Improve comments and naming
  - Convert macros to static inline functions
  - Remove superfluous `break' after `return'
  - Make sure we get a build-time error (undefined reference to
    'c2p_unsupported') in case of future misuse
  - Replace `unsigned long' by `u32' in comp(), as that's what all callers use
  - Use {get,put}_unaligned_be32() in store_planar{,_masked}()
  - Use void * for arbitrary pointers
  - Use a union to represent pixels/words, to avoid casts

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>

2 files changed, 99 insertions, 88 deletions

diff --git a/drivers/video/c2p.c b/drivers/video/c2p.c
index f102b578ce10..c170fff0d35e 100644
--- a/drivers/video/c2p.c
+++ b/drivers/video/c2p.c
@@ -1,7 +1,7 @@
 /*
  *  Fast C2P (Chunky-to-Planar) Conversion
  *
- *  Copyright (C) 2003 Geert Uytterhoeven
+ *  Copyright (C) 2003-2008 Geert Uytterhoeven
  *
  *  NOTES:
  *    - This code was inspired by Scout's C2P tutorial
@@ -14,6 +14,9 @@
 
 #include <linux/module.h>
 #include <linux/string.h>
+
+#include <asm/unaligned.h>
+
 #include "c2p.h"
 
 
@@ -21,97 +24,100 @@
      *  Basic transpose step
      */
 
-#define _transp(d, i1, i2, shift, mask)                         \
-        do {                                                    \
-                u32 t = (d[i1] ^ (d[i2] >> shift)) & mask;      \
-                d[i1] ^= t;                                     \
-                d[i2] ^= t << shift;                            \
-        } while (0)
+static inline void _transp(u32 d[], unsigned int i1, unsigned int i2,
+                           unsigned int shift, u32 mask)
+{
+        u32 t = (d[i1] ^ (d[i2] >> shift)) & mask;
+
+        d[i1] ^= t;
+        d[i2] ^= t << shift;
+}
 
-static inline u32 get_mask(int n)
+extern void c2p_unsupported(void);
+
+static inline u32 get_mask(unsigned int n)
 {
         switch (n) {
         case 1:
                 return 0x55555555;
-                break;
 
         case 2:
                 return 0x33333333;
-                break;
 
         case 4:
                 return 0x0f0f0f0f;
-                break;
 
         case 8:
                 return 0x00ff00ff;
-                break;
 
         case 16:
                 return 0x0000ffff;
-                break;
         }
+
+        c2p_unsupported();
         return 0;
 }
 
-#define transp_nx1(d, n)                                        \
-        do {                                                    \
-                u32 mask = get_mask(n);                         \
-                /* First block */                               \
-                _transp(d, 0, 1, n, mask);                      \
-                /* Second block */                              \
-                _transp(d, 2, 3, n, mask);                      \
-                /* Third block */                               \
-                _transp(d, 4, 5, n, mask);                      \
-                /* Fourth block */                              \
-                _transp(d, 6, 7, n, mask);                      \
-        } while (0)
-
-#define transp_nx2(d, n)                                        \
-        do {                                                    \
-                u32 mask = get_mask(n);                         \
-                /* First block */                               \
-                _transp(d, 0, 2, n, mask);                      \
-                _transp(d, 1, 3, n, mask);                      \
-                /* Second block */                              \
-                _transp(d, 4, 6, n, mask);                      \
-                _transp(d, 5, 7, n, mask);                      \
-        } while (0)
-
-#define transp_nx4(d, n)                                        \
-        do {                                                    \
-                u32 mask = get_mask(n);                         \
-                _transp(d, 0, 4, n, mask);                      \
-                _transp(d, 1, 5, n, mask);                      \
-                _transp(d, 2, 6, n, mask);                      \
-                _transp(d, 3, 7, n, mask);                      \
-        } while (0)
-
-#define transp(d, n, m) transp_nx ## m(d, n)
+static inline void transp8(u32 d[], unsigned int n, unsigned int m)
+{
+        u32 mask = get_mask(n);
+
+        switch (m) {
+        case 1:
+                /* First n x 1 block */
+                _transp(d, 0, 1, n, mask);
+                /* Second n x 1 block */
+                _transp(d, 2, 3, n, mask);
+                /* Third n x 1 block */
+                _transp(d, 4, 5, n, mask);
+                /* Fourth n x 1 block */
+                _transp(d, 6, 7, n, mask);
+                return;
+
+        case 2:
+                /* First n x 2 block */
+                _transp(d, 0, 2, n, mask);
+                _transp(d, 1, 3, n, mask);
+                /* Second n x 2 block */
+                _transp(d, 4, 6, n, mask);
+                _transp(d, 5, 7, n, mask);
+                return;
+
+        case 4:
+                /* Single n x 4 block */
+                _transp(d, 0, 4, n, mask);
+                _transp(d, 1, 5, n, mask);
+                _transp(d, 2, 6, n, mask);
+                _transp(d, 3, 7, n, mask);
+                return;
+        }
+
+        c2p_unsupported();
+}
 
 
     /*
      *  Perform a full C2P step on 32 8-bit pixels, stored in 8 32-bit words
      *  containing
      *    - 32 8-bit chunky pixels on input
-     *    - permuted planar data on output
+     *    - permutated planar data (1 plane per 32-bit word) on output
      */
 
-static void c2p_8bpp(u32 d[8])
+static void c2p_32x8(u32 d[8])
 {
-        transp(d, 16, 4);
-        transp(d, 8, 2);
-        transp(d, 4, 1);
-        transp(d, 2, 4);
-        transp(d, 1, 2);
+        transp8(d, 16, 4);
+        transp8(d, 8, 2);
+        transp8(d, 4, 1);
+        transp8(d, 2, 4);
+        transp8(d, 1, 2);
 }
 
 
     /*
-     *  Array containing the permution indices of the planar data after c2p
+     *  Array containing the permutation indices of the planar data after c2p
      */
 
-static const int perm_c2p_8bpp[8] = { 7, 5, 3, 1, 6, 4, 2, 0 };
+static const int perm_c2p_32x8[8] = { 7, 5, 3, 1, 6, 4, 2, 0 };
 
 
     /*
@@ -119,8 +125,7 @@ static const int perm_c2p_8bpp[8] = { 7, 5, 3, 1, 6, 4, 2, 0 };
      *  This is equivalent to (a & mask) | (b & ~mask)
      */
 
-static inline unsigned long comp(unsigned long a, unsigned long b,
-                                 unsigned long mask)
+static inline u32 comp(u32 a, u32 b, u32 mask)
 {
         return ((a ^ b) & mask) ^ b;
 }
@@ -130,12 +135,12 @@ static inline unsigned long comp(unsigned long a, unsigned long b,
      *  Store a full block of planar data after c2p conversion
      */
 
-static inline void store_planar(char *dst, u32 dst_inc, u32 bpp, u32 d[8])
+static inline void store_planar(void *dst, u32 dst_inc, u32 bpp, u32 d[8])
 {
         int i;
 
         for (i = 0; i < bpp; i++, dst += dst_inc)
-                *(u32 *)dst = d[perm_c2p_8bpp[i]];
+                put_unaligned_be32(d[perm_c2p_32x8[i]], dst);
 }
 
 
@@ -143,13 +148,15 @@ static inline void store_planar(char *dst, u32 dst_inc, u32 bpp, u32 d[8])
      *  Store a partial block of planar data after c2p conversion
      */
 
-static inline void store_planar_masked(char *dst, u32 dst_inc, u32 bpp,
+static inline void store_planar_masked(void *dst, u32 dst_inc, u32 bpp,
                                        u32 d[8], u32 mask)
 {
         int i;
 
         for (i = 0; i < bpp; i++, dst += dst_inc)
-                *(u32 *)dst = comp(d[perm_c2p_8bpp[i]], *(u32 *)dst, mask);
+                put_unaligned_be32(comp(d[perm_c2p_32x8[i]],
+                                        get_unaligned_be32(dst), mask),
+                                   dst);
 }
 
 
@@ -166,18 +173,21 @@ static inline void store_planar_masked(char *dst, u32 dst_inc, u32 bpp,
      *  @bpp: Bits per pixel of the planar frame buffer (1-8)
      */
 
-void c2p(u8 *dst, const u8 *src, u32 dx, u32 dy, u32 width, u32 height,
+void c2p(void *dst, const void *src, u32 dx, u32 dy, u32 width, u32 height,
          u32 dst_nextline, u32 dst_nextplane, u32 src_nextline, u32 bpp)
 {
-        int dst_idx;
-        u32 d[8], first, last, w;
+        union {
+                u8 pixels[32];
+                u32 words[8];
+        } d;
+        u32 dst_idx, first, last, w;
         const u8 *c;
-        u8 *p;
+        void *p;
 
         dst += dy*dst_nextline+(dx & ~31);
         dst_idx = dx % 32;
-        first = ~0UL >> dst_idx;
-        last = ~(~0UL >> ((dst_idx+width) % 32));
+        first = 0xffffffffU >> dst_idx;
+        last = ~(0xffffffffU >> ((dst_idx+width) % 32));
         while (height--) {
                 c = src;
                 p = dst;
@@ -185,11 +195,12 @@ void c2p(u8 *dst, const u8 *src, u32 dx, u32 dy, u32 width, u32 height,
                 if (dst_idx+width <= 32) {
                         /* Single destination word */
                         first &= last;
-                        memset(d, 0, sizeof(d));
-                        memcpy((u8 *)d+dst_idx, c, width);
+                        memset(d.pixels, 0, sizeof(d));
+                        memcpy(d.pixels+dst_idx, c, width);
                         c += width;
-                        c2p_8bpp(d);
-                        store_planar_masked(p, dst_nextplane, bpp, d, first);
+                        c2p_32x8(d.words);
+                        store_planar_masked(p, dst_nextplane, bpp, d.words,
+                                            first);
                         p += 4;
                 } else {
                         /* Multiple destination words */
@@ -197,32 +208,32 @@ void c2p(u8 *dst, const u8 *src, u32 dx, u32 dy, u32 width, u32 height,
                         /* Leading bits */
                         if (dst_idx) {
                                 w = 32 - dst_idx;
-                                memset(d, 0, dst_idx);
-                                memcpy((u8 *)d+dst_idx, c, w);
+                                memset(d.pixels, 0, dst_idx);
+                                memcpy(d.pixels+dst_idx, c, w);
                                 c += w;
-                                c2p_8bpp(d);
-                                store_planar_masked(p, dst_nextplane, bpp, d,
-                                                    first);
+                                c2p_32x8(d.words);
+                                store_planar_masked(p, dst_nextplane, bpp,
+                                                    d.words, first);
                                 p += 4;
                                 w = width-w;
                         }
                         /* Main chunk */
                         while (w >= 32) {
-                                memcpy(d, c, 32);
+                                memcpy(d.pixels, c, 32);
                                 c += 32;
-                                c2p_8bpp(d);
-                                store_planar(p, dst_nextplane, bpp, d);
+                                c2p_32x8(d.words);
+                                store_planar(p, dst_nextplane, bpp, d.words);
                                 p += 4;
                                 w -= 32;
                         }
                         /* Trailing bits */
                         w %= 32;
                         if (w > 0) {
-                                memcpy(d, c, w);
-                                memset((u8 *)d+w, 0, 32-w);
-                                c2p_8bpp(d);
-                                store_planar_masked(p, dst_nextplane, bpp, d,
-                                                    last);
+                                memcpy(d.pixels, c, w);
+                                memset(d.pixels+w, 0, 32-w);
+                                c2p_32x8(d.words);
+                                store_planar_masked(p, dst_nextplane, bpp,
+                                                    d.words, last);
                         }
                 }
                 src += src_nextline;
diff --git a/drivers/video/c2p.h b/drivers/video/c2p.h
index c77cbf17e043..daafd872601c 100644
--- a/drivers/video/c2p.h
+++ b/drivers/video/c2p.h
@@ -10,7 +10,7 @@
 
 #include <linux/types.h>
 
-extern void c2p(u8 *dst, const u8 *src, u32 dx, u32 dy, u32 width, u32 height,
-                u32 dst_nextline, u32 dst_nextplane, u32 src_nextline,
-                u32 bpp);
+extern void c2p(void *dst, const void *src, u32 dx, u32 dy, u32 width,
+                u32 height, u32 dst_nextline, u32 dst_nextplane,
+                u32 src_nextline, u32 bpp);