linux-kernel - [PATCH 2/2] Docs/EDID: Calculate CRC while building the code

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Message-ID: <1541407715-5417-3-git-send-email-cniedermaier@dh-electronics.de>
Date:   Mon, 5 Nov 2018 09:48:35 +0100
From:   Christoph Niedermaier <cniedermaier@...electronics.de>
To:     <corbet@....net>, <linux-doc@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <C.Emde@...dl.org>
Subject: [PATCH 2/2] Docs/EDID: Calculate CRC while building the code

The previous version made it necessary to first generate an
EDID data set without correct CRC and then to fix the CRC in
a second step. This patch adds the CRC calculation to the
makefile in such a way that a correct EDID data set is generated
in a single build step. Successfully tested with all existing
and a couple of new data sets.

Signed-off-by: Christoph Niedermaier <cniedermaier@...electronics.de>
Reviewed-by: Carsten Emde <C.Emde@...dl.org>
---
 Documentation/EDID/1024x768.S  |  1 -
 Documentation/EDID/1280x1024.S |  1 -
 Documentation/EDID/1600x1200.S |  1 -
 Documentation/EDID/1680x1050.S |  1 -
 Documentation/EDID/1920x1080.S |  1 -
 Documentation/EDID/800x600.S   |  1 -
 Documentation/EDID/HOWTO.txt   |  9 ---------
 Documentation/EDID/Makefile    | 15 +++++++++++++--
 8 files changed, 13 insertions(+), 17 deletions(-)

diff --git a/Documentation/EDID/1024x768.S b/Documentation/EDID/1024x768.S
index ff4013e..4aed3f9 100644
--- a/Documentation/EDID/1024x768.S
+++ b/Documentation/EDID/1024x768.S
@@ -39,6 +39,5 @@
 #define ESTABLISHED_TIMING2_BITS 0x08 /* Bit 3 -> 1024x768 @60 Hz */
 #define HSYNC_POL 0
 #define VSYNC_POL 0
-#define CRC 0x55
 
 #include "edid.S"
diff --git a/Documentation/EDID/1280x1024.S b/Documentation/EDID/1280x1024.S
index ce0e85b..b26dd42 100644
--- a/Documentation/EDID/1280x1024.S
+++ b/Documentation/EDID/1280x1024.S
@@ -39,6 +39,5 @@
 /* No ESTABLISHED_TIMINGx_BITS */
 #define HSYNC_POL 1
 #define VSYNC_POL 1
-#define CRC 0xa0
 
 #include "edid.S"
diff --git a/Documentation/EDID/1600x1200.S b/Documentation/EDID/1600x1200.S
index 5eeb751..0d091b2 100644
--- a/Documentation/EDID/1600x1200.S
+++ b/Documentation/EDID/1600x1200.S
@@ -39,6 +39,5 @@
 /* No ESTABLISHED_TIMINGx_BITS */
 #define HSYNC_POL 1
 #define VSYNC_POL 1
-#define CRC 0x9d
 
 #include "edid.S"
diff --git a/Documentation/EDID/1680x1050.S b/Documentation/EDID/1680x1050.S
index ec67950..7dfed9a 100644
--- a/Documentation/EDID/1680x1050.S
+++ b/Documentation/EDID/1680x1050.S
@@ -39,6 +39,5 @@
 /* No ESTABLISHED_TIMINGx_BITS */
 #define HSYNC_POL 1
 #define VSYNC_POL 1
-#define CRC 0x26
 
 #include "edid.S"
diff --git a/Documentation/EDID/1920x1080.S b/Documentation/EDID/1920x1080.S
index e0657af..d6ffbba 100644
--- a/Documentation/EDID/1920x1080.S
+++ b/Documentation/EDID/1920x1080.S
@@ -39,6 +39,5 @@
 /* No ESTABLISHED_TIMINGx_BITS */
 #define HSYNC_POL 1
 #define VSYNC_POL 1
-#define CRC 0x05
 
 #include "edid.S"
diff --git a/Documentation/EDID/800x600.S b/Documentation/EDID/800x600.S
index b6853b2..a561658 100644
--- a/Documentation/EDID/800x600.S
+++ b/Documentation/EDID/800x600.S
@@ -36,6 +36,5 @@
 #define ESTABLISHED_TIMING1_BITS 0x01 /* Bit 0: 800x600 @ 60Hz */
 #define HSYNC_POL 1
 #define VSYNC_POL 1
-#define CRC 0xc2
 
 #include "edid.S"
diff --git a/Documentation/EDID/HOWTO.txt b/Documentation/EDID/HOWTO.txt
index 7d05a7d..539871c 100644
--- a/Documentation/EDID/HOWTO.txt
+++ b/Documentation/EDID/HOWTO.txt
@@ -47,12 +47,3 @@ EDID:
 #define YBLANK vtotal-vdisp
 #define YOFFSET vsyncstart-vdisp
 #define YPULSE vsyncend-vsyncstart
-
-The CRC value in the last line
-  #define CRC 0x55
-also is a bit tricky. After a first version of the binary data set is
-created, it must be checked with the "edid-decode" utility which will
-most probably complain about a wrong CRC. Fortunately, the utility also
-displays the correct CRC which must then be inserted into the source
-file. After the make procedure is repeated, the EDID data set is ready
-to be used.
diff --git a/Documentation/EDID/Makefile b/Documentation/EDID/Makefile
index 17763ca..85a927d 100644
--- a/Documentation/EDID/Makefile
+++ b/Documentation/EDID/Makefile
@@ -15,10 +15,21 @@ clean:
 %.o:	%.S
 	@cc -c $^
 
-%.bin:	%.o
+%.bin.nocrc:	%.o
 	@objcopy -Obinary $^ $@
 
-%.bin.ihex:	%.o
+%.crc:	%.bin.nocrc
+	@list=$$(for i in `seq 1 127`; do head -c$$i $^ | tail -c1 \
+		| hexdump -v -e '/1 "%02X+"'; done); \
+		echo "ibase=16;100-($${list%?})%100" | bc >$@
+
+%.p:	%.crc %.S
+	@cc -c -DCRC="$$(cat $*.crc)" -o $@ $*.S
+
+%.bin:	%.p
+	@objcopy -Obinary $^ $@
+
+%.bin.ihex:	%.p
 	@objcopy -Oihex $^ $@
 	@dos2unix $@ 2>/dev/null
 
-- 
2.1.4