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Diffstat (limited to 'qemu/roms/u-boot/doc/README.displaying-bmps')
| -rw-r--r-- | qemu/roms/u-boot/doc/README.displaying-bmps | 27 |
1 files changed, 0 insertions, 27 deletions
diff --git a/qemu/roms/u-boot/doc/README.displaying-bmps b/qemu/roms/u-boot/doc/README.displaying-bmps deleted file mode 100644 index 331154166..000000000 --- a/qemu/roms/u-boot/doc/README.displaying-bmps +++ /dev/null @@ -1,27 +0,0 @@ -If you are experiencing hangups/data-aborts when trying to display a BMP image, -the following might be relevant to your situation... - -Some architectures cannot handle unaligned memory accesses, and an attempt to -perform one will lead to a data abort. On such architectures it is necessary to -make sure all data is properly aligned, and in many situations simply choosing -a 32 bit aligned address is enough to ensure proper alignment. This is not -always the case when dealing with data that has an internal layout such as a -BMP image: - -BMP images have a header that starts with 2 byte-size fields followed by mostly -32 bit fields. The packed struct that represents this header can be seen below: - -typedef struct bmp_header { - /* Header */ - char signature[2]; - __u32 file_size; - __u32 reserved; - __u32 data_offset; - ... etc -} __attribute__ ((packed)) bmp_header_t; - -When placed in an aligned address such as 0x80a00000, char signature offsets -the __u32 fields into unaligned addresses (in our example 0x80a00002, -0x80a00006, and so on...). When these fields are accessed by U-Boot, a 32 bit -access is generated at a non-32-bit-aligned address, causing a data abort. -The proper alignment for BMP images is therefore: 32-bit-aligned-address + 2. |