cbgfx: make the code more descriptive

This change makes the code in graphics.c more descriptive and readable.
Especially, it makes expressions for scale calculation look what they
are meant to do. It also includes:

- Rename variables (struct fraction, dim_org, etc.) for more consistency
- Add more input validation (div-by-zero, etc.)

BUG=chromium:502066
BRANCH=master
TEST=Tested on Samus
CQ-DEPEND=CL:304860

Change-Id: I2694912bb7b6017d5655de2fd655b95432addb22
Signed-off-by: Patrick Georgi <pgeorgi@google.com>
Original-Commit-Id: 0863dc3ee925d3a05c83c66397b19a57f5478ef3
Original-Change-Id: Id8e349b8e09082fb84c3e1a984617f916e16c518
Original-Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/304861
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/11928
Tested-by: build bot (Jenkins)

1 files changed, 3 insertions, 4 deletions

diff --git a/payloads/libpayload/include/cbgfx.h b/payloads/libpayload/include/cbgfx.h
index ffd8534d13..54d395395a 100644
--- a/payloads/libpayload/include/cbgfx.h
+++ b/payloads/libpayload/include/cbgfx.h
@@ -30,8 +30,8 @@
 #define CBGFX_ERROR_SCALE_OUT_OF_RANGE	0x13
 
 struct fraction {
-	int32_t nume;
-	int32_t deno;
+	int32_t n;
+	int32_t d;
 };
 
 struct scale {
@@ -147,5 +147,4 @@ int draw_bitmap(const void *bitmap, size_t size,
  * @return CBGFX_* error codes
  */
 int draw_bitmap_direct(const void *bitmap, size_t size,
-		       const struct vector *pos);
-
+		       const struct vector *top_left);