cfb_console: force natural alignment of unzipped bitmap images

Bitmaps contain 32-bit integers aligned at offsets of +2, +6 within the bmp_header structure. This patch forces them to be aligned properly when gzipped bitmaps are used.

Refer to these files for more details:
doc/README.displaying-bmps
doc/README.arm-unaligned-accesses

---
 drivers/video/cfb_console.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

index 6db4073..2209148 100644
@@ -1473,7 +1473,10 @@ int video_display_bitmap(ulong bmp_image, int x, int y)
 			printf("Error: malloc in gunzip failed!\n");
 			return 1;
 		}
-		if (gunzip(dst, CONFIG_SYS_VIDEO_LOGO_MAX_SIZE,
+		/* NB: we need to force offset of +2
+		 * See doc/README.displaying-bmps
+		 */
+		if (gunzip(dst+2, CONFIG_SYS_VIDEO_LOGO_MAX_SIZE-2,
 			   (uchar *) bmp_image,
 			   &len) != 0) {
 			printf("Error: no valid bmp or bmp.gz image at %lx\n",

@@ -1489,7 +1492,7 @@ int video_display_bitmap(ulong bmp_image, int x, int y)
 		/*
 		 * Set addr to decompressed image
 		 */
-		bmp = (bmp_image_t *) dst;
+		bmp = (bmp_image_t *)(dst+2);
 
 		if (!((bmp->header.signature[0] == 'B') &&
 		      (bmp->header.signature[1] == 'M'))) {

1.8.3.2

Dear Eric Nelson,

This makes no sense to me. In the Subject: you talk about "unzipped bitmap images", but here you write about "gzipped bitmaps".

I think I understand what you mean, but this needs better wording.

DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
There are three ways to get something done:
        (1) Do it yourself.
        (2) Hire someone to do it for you.
        (3) Forbid your kids to do it.

.bmp files contain 32-bit integers aligned at offsets of +2, +6, et cetera within the bmp_header structure (see include/bmp_layout.h).

Support for gzip-compressed .bmp files is present in the cfb_console display subsystem by uncompressing them prior to use.

This patch forces the in-memory header to be aligned properly for these compressed images by extracting them to a 2-byte offset in the memory returned by malloc. Since malloc will always return a 4-byte aligned value, this forces the .bmp header fields to be naturally aligned on 4-byte addresses.

Refer to these files for more details:
doc/README.displaying-bmps
doc/README.arm-unaligned-accesses

---
Changes in V2:
- re-worded the subject line
- expanded and re-worded the commit message
Changes in V3:
- shortened the subject line
- fixed multiline comment style
- added patch history
- sent with "In-Reply-To" header referring to V1 See also:
V1: http://patchwork.ozlabs.org/patch/323243/
V2: http://patchwork.ozlabs.org/patch/325348/

 drivers/video/cfb_console.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

index 6db4073..b52e9ed 100644
@@ -1473,7 +1473,11 @@ int video_display_bitmap(ulong bmp_image, int x, int y)
 			printf("Error: malloc in gunzip failed!\n");
 			return 1;
 		}
-		if (gunzip(dst, CONFIG_SYS_VIDEO_LOGO_MAX_SIZE,
+		/*
+		 * NB: we need to force offset of +2
+		 * See doc/README.displaying-bmps
+		 */
+		if (gunzip(dst+2, CONFIG_SYS_VIDEO_LOGO_MAX_SIZE-2,
 			   (uchar *) bmp_image,
 			   &len) != 0) {
 			printf("Error: no valid bmp or bmp.gz image at %lx\n",

@@ -1489,7 +1493,7 @@ int video_display_bitmap(ulong bmp_image, int x, int y)
 		/*
 		 * Set addr to decompressed image
 		 */
-		bmp = (bmp_image_t *) dst;
+		bmp = (bmp_image_t *)(dst+2);
 
 		if (!((bmp->header.signature[0] == 'B') &&
 		      (bmp->header.signature[1] == 'M'))) {

1.8.3.2

Applied to u-boot/master, thanks!

Tom
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