[U-Boot] [PATCH] cfb_console: force natural alignment of unzipped bitmap images

[U-Boot] [PATCH] cfb_console: force natural alignment of unzipped bitmap images

[Eric Nelson]

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

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
---
 drivers/video/cfb_console.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/video/cfb_console.c b/drivers/video/cfb_console.c
index 6db4073..2209148 100644
--- a/drivers/video/cfb_console.c
+++ b/drivers/video/cfb_console.c
@@ -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

[U-Boot] [PATCH] cfb_console: force natural alignment of unzipped bitmap images

[Wolfgang Denk]

Dear Eric Nelson,

In message <1393103071-2788-1-git-send-email-eric.nelson@boundarydevices.com> you wrote:
> 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.

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.

> -		if (gunzip(dst, CONFIG_SYS_VIDEO_LOGO_MAX_SIZE,
> +		/* NB: we need to force offset of +2
> +		 * See doc/README.displaying-bmps

Incorrect multiline comment style.


Best regards,

Wolfgang Denk

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There are three ways to get something done:
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[U-Boot] [PATCH V3] cfb_console: align fields in gzipped .bmp files

[Eric Nelson]

.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

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
---
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(-)

diff --git a/drivers/video/cfb_console.c b/drivers/video/cfb_console.c
index 6db4073..b52e9ed 100644
--- a/drivers/video/cfb_console.c
+++ b/drivers/video/cfb_console.c
@@ -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

[U-Boot] [U-Boot, V3] cfb_console: align fields in gzipped .bmp files

[Tom Rini]

On Sat, Mar 08, 2014 at 07:55:52AM -0700, Eric Nelson wrote:

> .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
> 
> Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>

Applied to u-boot/master, thanks!

-- 
Tom
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