drm: allow loading an EDID as firmware to override broken monitor

Broken monitors and/or broken graphic boards may send erroneous or no
EDID data. This also applies to broken KVM devices that are unable to
correctly forward the EDID data of the connected monitor but invent
their own fantasy data.

This patch allows to specify an EDID data set to be used instead of
probing the monitor for it. It contains built-in data sets of frequently
used screen resolutions. In addition, a particular EDID data set may be
provided in the /lib/firmware directory and loaded via the firmware
interface. The name is passed to the kernel as module parameter of the
drm_kms_helper module either when loaded
  options drm_kms_helper edid_firmware=edid/1280x1024.bin
or as kernel commandline parameter
  drm_kms_helper.edid_firmware=edid/1280x1024.bin

It is also possible to restrict the usage of a specified EDID data set
to a particular connector. This is done by prepending the name of the
connector to the name of the EDID data set using the syntax
  edid_firmware=[<connector>:]<edid>
such as, for example,
  edid_firmware=DVI-I-1:edid/1920x1080.bin
in which case no other connector will be affected.

The built-in data sets are
Resolution    Name
--------------------------------
1024x768      edid/1024x768.bin
1280x1024     edid/1280x1024.bin
1680x1050     edid/1680x1050.bin
1920x1080     edid/1920x1080.bin

They are ignored, if a file with the same name is available in the
/lib/firmware directory.

The built-in EDID data sets are based on standard timings that may not
apply to a particular monitor and even crash it. Ideally, EDID data of
the connected monitor should be used. They may be obtained through the
drm/cardX/cardX-<connector>/edid entry in the /sys/devices PCI directory
of a correctly working graphics adapter.

It is even possible to specify the name of an EDID data set on-the-fly
via the /sys/module interface, e.g.
echo edid/myedid.bin >/sys/module/drm_kms_helper/parameters/edid_firmware
The new screen mode is considered when the related kernel function is
called for the first time after the change. Such calls are made when the
X server is started or when the display settings dialog is opened in an
already running X server.
Signed-off-by: NCarsten Emde <C.Emde@osadl.org>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Documentation/EDID/1024x768.S

+/*
+   1024x768.S: EDID data set for standard 1024x768 60 Hz monitor
+
+   Copyright (C) 2011 Carsten Emde <C.Emde@osadl.org>
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; either version 2
+   of the License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA.
+*/
+
+/* EDID */
+#define VERSION 1
+#define REVISION 3
+
+/* Display */
+#define CLOCK 65000 /* kHz */
+#define XPIX 1024
+#define YPIX 768
+#define XY_RATIO XY_RATIO_4_3
+#define XBLANK 320
+#define YBLANK 38
+#define XOFFSET 8
+#define XPULSE 144
+#define YOFFSET (63+3)
+#define YPULSE (63+6)
+#define DPI 72
+#define VFREQ 60 /* Hz */
+#define TIMING_NAME "Linux XGA"
+#define ESTABLISHED_TIMINGS_BITS 0x08 /* Bit 3 -> 1024x768 @60 Hz */
+#define HSYNC_POL 0
+#define VSYNC_POL 0
+#define CRC 0x55
+
+#include "edid.S"

Documentation/EDID/1280x1024.S

+/*
+   1280x1024.S: EDID data set for standard 1280x1024 60 Hz monitor
+
+   Copyright (C) 2011 Carsten Emde <C.Emde@osadl.org>
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; either version 2
+   of the License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA.
+*/
+
+/* EDID */
+#define VERSION 1
+#define REVISION 3
+
+/* Display */
+#define CLOCK 108000 /* kHz */
+#define XPIX 1280
+#define YPIX 1024
+#define XY_RATIO XY_RATIO_5_4
+#define XBLANK 408
+#define YBLANK 42
+#define XOFFSET 48
+#define XPULSE 112
+#define YOFFSET (63+1)
+#define YPULSE (63+3)
+#define DPI 72
+#define VFREQ 60 /* Hz */
+#define TIMING_NAME "Linux SXGA"
+#define ESTABLISHED_TIMINGS_BITS 0x00 /* none */
+#define HSYNC_POL 1
+#define VSYNC_POL 1
+#define CRC 0xa0
+
+#include "edid.S"

Documentation/EDID/1680x1050.S

+/*
+   1680x1050.S: EDID data set for standard 1680x1050 60 Hz monitor
+
+   Copyright (C) 2012 Carsten Emde <C.Emde@osadl.org>
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; either version 2
+   of the License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA.
+*/
+
+/* EDID */
+#define VERSION 1
+#define REVISION 3
+
+/* Display */
+#define CLOCK 146250 /* kHz */
+#define XPIX 1680
+#define YPIX 1050
+#define XY_RATIO XY_RATIO_16_10
+#define XBLANK 560
+#define YBLANK 39
+#define XOFFSET 104
+#define XPULSE 176
+#define YOFFSET (63+3)
+#define YPULSE (63+6)
+#define DPI 96
+#define VFREQ 60 /* Hz */
+#define TIMING_NAME "Linux WSXGA"
+#define ESTABLISHED_TIMINGS_BITS 0x00 /* none */
+#define HSYNC_POL 1
+#define VSYNC_POL 1
+#define CRC 0x26
+
+#include "edid.S"

Documentation/EDID/1920x1080.S

+/*
+   1920x1080.S: EDID data set for standard 1920x1080 60 Hz monitor
+
+   Copyright (C) 2012 Carsten Emde <C.Emde@osadl.org>
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; either version 2
+   of the License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA.
+*/
+
+/* EDID */
+#define VERSION 1
+#define REVISION 3
+
+/* Display */
+#define CLOCK 148500 /* kHz */
+#define XPIX 1920
+#define YPIX 1080
+#define XY_RATIO XY_RATIO_16_9
+#define XBLANK 280
+#define YBLANK 45
+#define XOFFSET 88
+#define XPULSE 44
+#define YOFFSET (63+4)
+#define YPULSE (63+5)
+#define DPI 96
+#define VFREQ 60 /* Hz */
+#define TIMING_NAME "Linux FHD"
+#define ESTABLISHED_TIMINGS_BITS 0x00 /* none */
+#define HSYNC_POL 1
+#define VSYNC_POL 1
+#define CRC 0x05
+
+#include "edid.S"

Documentation/EDID/HOWTO.txt

+In the good old days when graphics parameters were configured explicitly
+in a file called xorg.conf, even broken hardware could be managed.
+
+Today, with the advent of Kernel Mode Setting, a graphics board is
+either correctly working because all components follow the standards -
+or the computer is unusable, because the screen remains dark after
+booting or it displays the wrong area. Cases when this happens are:
+- The graphics board does not recognize the monitor.
+- The graphics board is unable to detect any EDID data.
+- The graphics board incorrectly forwards EDID data to the driver.
+- The monitor sends no or bogus EDID data.
+- A KVM sends its own EDID data instead of querying the connected monitor.
+Adding the kernel parameter "nomodeset" helps in most cases, but causes
+restrictions later on.
+
+As a remedy for such situations, the kernel configuration item
+CONFIG_DRM_LOAD_EDID_FIRMWARE was introduced. It allows to provide an
+individually prepared or corrected EDID data set in the /lib/firmware
+directory from where it is loaded via the firmware interface. The code
+(see drivers/gpu/drm/drm_edid_load.c) contains built-in data sets for
+commonly used screen resolutions (1024x768, 1280x1024, 1680x1050,
+1920x1080) as binary blobs, but the kernel source tree does not contain
+code to create these data. In order to elucidate the origin of the
+built-in binary EDID blobs and to facilitate the creation of individual
+data for a specific misbehaving monitor, commented sources and a
+Makefile environment are given here.
+
+To create binary EDID and C source code files from the existing data
+material, simply type "make".
+
+If you want to create your own EDID file, copy the file 1024x768.S and
+replace the settings with your own data. The CRC value in the last line
+  #define CRC 0x55
+is a bit tricky. After a first version of the binary data set is
+created, it must be 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.

Documentation/EDID/Makefile

+
+SOURCES	:= $(wildcard [0-9]*x[0-9]*.S)
+
+BIN	:= $(patsubst %.S, %.bin, $(SOURCES))
+
+IHEX	:= $(patsubst %.S, %.bin.ihex, $(SOURCES))
+
+CODE	:= $(patsubst %.S, %.c, $(SOURCES))
+
+all:	$(BIN) $(IHEX) $(CODE)
+
+clean:
+	@rm -f *.o *.bin.ihex *.bin *.c
+
+%.o:	%.S
+	@cc -c $^
+
+%.bin:	%.o
+	@objcopy -Obinary $^ $@
+
+%.bin.ihex:	%.o
+	@objcopy -Oihex $^ $@
+	@dos2unix $@ 2>/dev/null
+
+%.c:	%.bin
+	@echo "{" >$@; hexdump -f hex $^ >>$@; echo "};" >>$@

Documentation/EDID/edid.S

+/*
+   edid.S: EDID data template
+
+   Copyright (C) 2012 Carsten Emde <C.Emde@osadl.org>
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; either version 2
+   of the License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA.
+*/
+
+
+/* Manufacturer */
+#define MFG_LNX1 'L'
+#define MFG_LNX2 'N'
+#define MFG_LNX3 'X'
+#define SERIAL 0
+#define YEAR 2012
+#define WEEK 5
+
+/* EDID 1.3 standard definitions */
+#define XY_RATIO_16_10	0b00
+#define XY_RATIO_4_3	0b01
+#define XY_RATIO_5_4	0b10
+#define XY_RATIO_16_9	0b11
+
+#define mfgname2id(v1,v2,v3) \
+	((((v1-'@')&0x1f)<<10)+(((v2-'@')&0x1f)<<5)+((v3-'@')&0x1f))
+#define swap16(v1) ((v1>>8)+((v1&0xff)<<8))
+#define msbs2(v1,v2) ((((v1>>8)&0x0f)<<4)+((v2>>8)&0x0f))
+#define msbs4(v1,v2,v3,v4) \
+	(((v1&0x03)>>2)+((v2&0x03)>>4)+((v3&0x03)>>6)+((v4&0x03)>>8))
+#define pixdpi2mm(pix,dpi) ((pix*25)/dpi)
+#define xsize pixdpi2mm(XPIX,DPI)
+#define ysize pixdpi2mm(YPIX,DPI)
+
+		.data
+
+/* Fixed header pattern */
+header:		.byte	0x00,0xff,0xff,0xff,0xff,0xff,0xff,0x00
+
+mfg_id:		.word	swap16(mfgname2id(MFG_LNX1, MFG_LNX2, MFG_LNX3))
+
+prod_code:	.word	0
+
+/* Serial number. 32 bits, little endian. */
+serial_number:	.long	SERIAL
+
+/* Week of manufacture */
+week:		.byte	WEEK
+
+/* Year of manufacture, less 1990. (1990-2245)
+   If week=255, it is the model year instead */
+year:		.byte	YEAR-1990
+
+version:	.byte	VERSION 	/* EDID version, usually 1 (for 1.3) */
+revision:	.byte	REVISION	/* EDID revision, usually 3 (for 1.3) */
+
+/* If Bit 7=1	Digital input. If set, the following bit definitions apply:
+     Bits 6-1	Reserved, must be 0
+     Bit 0	Signal is compatible with VESA DFP 1.x TMDS CRGB,
+		  1 pixel per clock, up to 8 bits per color, MSB aligned,
+   If Bit 7=0	Analog input. If clear, the following bit definitions apply:
+     Bits 6-5	Video white and sync levels, relative to blank
+		  00=+0.7/-0.3 V; 01=+0.714/-0.286 V;
+		  10=+1.0/-0.4 V; 11=+0.7/0 V
+   Bit 4	Blank-to-black setup (pedestal) expected
+   Bit 3	Separate sync supported
+   Bit 2	Composite sync (on HSync) supported
+   Bit 1	Sync on green supported
+   Bit 0	VSync pulse must be serrated when somposite or
+		  sync-on-green is used. */
+video_parms:	.byte	0x6d
+
+/* Maximum horizontal image size, in centimetres
+   (max 292 cm/115 in at 16:9 aspect ratio) */
+max_hor_size:	.byte	xsize/10
+
+/* Maximum vertical image size, in centimetres.
+   If either byte is 0, undefined (e.g. projector) */
+max_vert_size:	.byte	ysize/10
+
+/* Display gamma, minus 1, times 100 (range 1.00-3.5 */
+gamma:		.byte	120
+
+/* Bit 7	DPMS standby supported
+   Bit 6	DPMS suspend supported
+   Bit 5	DPMS active-off supported
+   Bits 4-3	Display type: 00=monochrome; 01=RGB colour;
+		  10=non-RGB multicolour; 11=undefined
+   Bit 2	Standard sRGB colour space. Bytes 25-34 must contain
+		  sRGB standard values.
+   Bit 1	Preferred timing mode specified in descriptor block 1.
+   Bit 0	GTF supported with default parameter values. */
+dsp_features:	.byte	0xea
+
+/* Chromaticity coordinates. */
+/* Red and green least-significant bits
+   Bits 7-6	Red x value least-significant 2 bits
+   Bits 5-4	Red y value least-significant 2 bits
+   Bits 3-2	Green x value lst-significant 2 bits
+   Bits 1-0	Green y value least-significant 2 bits */
+red_green_lsb:	.byte	0x5e
+
+/* Blue and white least-significant 2 bits */
+blue_white_lsb:	.byte	0xc0
+
+/* Red x value most significant 8 bits.
+   0-255 encodes 0-0.996 (255/256); 0-0.999 (1023/1024) with lsbits */
+red_x_msb:	.byte	0xa4
+
+/* Red y value most significant 8 bits */
+red_y_msb:	.byte	0x59
+
+/* Green x and y value most significant 8 bits */
+green_x_y_msb:	.byte	0x4a,0x98
+
+/* Blue x and y value most significant 8 bits */
+blue_x_y_msb:	.byte	0x25,0x20
+
+/* Default white point x and y value most significant 8 bits */
+white_x_y_msb:	.byte	0x50,0x54
+
+/* Established timings */
+/* Bit 7	720x400 @ 70 Hz
+   Bit 6	720x400 @ 88 Hz
+   Bit 5	640x480 @ 60 Hz
+   Bit 4	640x480 @ 67 Hz
+   Bit 3	640x480 @ 72 Hz
+   Bit 2	640x480 @ 75 Hz
+   Bit 1	800x600 @ 56 Hz
+   Bit 0	800x600 @ 60 Hz */
+estbl_timing1:	.byte	0x00
+
+/* Bit 7	800x600 @ 72 Hz
+   Bit 6	800x600 @ 75 Hz
+   Bit 5	832x624 @ 75 Hz
+   Bit 4	1024x768 @ 87 Hz, interlaced (1024x768)
+   Bit 3	1024x768 @ 60 Hz
+   Bit 2	1024x768 @ 72 Hz
+   Bit 1	1024x768 @ 75 Hz
+   Bit 0	1280x1024 @ 75 Hz */
+estbl_timing2:	.byte	ESTABLISHED_TIMINGS_BITS
+
+/* Bit 7	1152x870 @ 75 Hz (Apple Macintosh II)
+   Bits 6-0 	Other manufacturer-specific display mod */
+estbl_timing3:	.byte	0x00
+
+/* Standard timing */
+/* X resolution, less 31, divided by 8 (256-2288 pixels) */
+std_xres:	.byte	(XPIX/8)-31
+/* Y resolution, X:Y pixel ratio
+   Bits 7-6	X:Y pixel ratio: 00=16:10; 01=4:3; 10=5:4; 11=16:9.
+   Bits 5-0	Vertical frequency, less 60 (60-123 Hz) */
+std_vres:	.byte	(XY_RATIO<<6)+VFREQ-60
+		.fill	7,2,0x0101	/* Unused */
+
+descriptor1:
+/* Pixel clock in 10 kHz units. (0.-655.35 MHz, little-endian) */
+clock:		.word	CLOCK/10
+
+/* Horizontal active pixels 8 lsbits (0-4095) */
+x_act_lsb:	.byte	XPIX&0xff
+/* Horizontal blanking pixels 8 lsbits (0-4095)
+   End of active to start of next active. */
+x_blk_lsb:	.byte	XBLANK&0xff
+/* Bits 7-4 	Horizontal active pixels 4 msbits
+   Bits 3-0	Horizontal blanking pixels 4 msbits */
+x_msbs:		.byte	msbs2(XPIX,XBLANK)
+
+/* Vertical active lines 8 lsbits (0-4095) */
+y_act_lsb:	.byte	YPIX&0xff
+/* Vertical blanking lines 8 lsbits (0-4095) */
+y_blk_lsb:	.byte	YBLANK&0xff
+/* Bits 7-4 	Vertical active lines 4 msbits
+   Bits 3-0 	Vertical blanking lines 4 msbits */
+y_msbs:		.byte	msbs2(YPIX,YBLANK)
+
+/* Horizontal sync offset pixels 8 lsbits (0-1023) From blanking start */
+x_snc_off_lsb:	.byte	XOFFSET&0xff
+/* Horizontal sync pulse width pixels 8 lsbits (0-1023) */
+x_snc_pls_lsb:	.byte	XPULSE&0xff
+/* Bits 7-4 	Vertical sync offset lines 4 lsbits -63)
+   Bits 3-0 	Vertical sync pulse width lines 4 lsbits -63) */
+y_snc_lsb:	.byte	((YOFFSET-63)<<4)+(YPULSE-63)
+/* Bits 7-6 	Horizontal sync offset pixels 2 msbits
+   Bits 5-4 	Horizontal sync pulse width pixels 2 msbits
+   Bits 3-2 	Vertical sync offset lines 2 msbits
+   Bits 1-0 	Vertical sync pulse width lines 2 msbits */
+xy_snc_msbs:	.byte	msbs4(XOFFSET,XPULSE,YOFFSET,YPULSE)
+
+/* Horizontal display size, mm, 8 lsbits (0-4095 mm, 161 in) */
+x_dsp_size:	.byte	xsize&0xff
+
+/* Vertical display size, mm, 8 lsbits (0-4095 mm, 161 in) */
+y_dsp_size:	.byte	ysize&0xff
+
+/* Bits 7-4 	Horizontal display size, mm, 4 msbits
+   Bits 3-0 	Vertical display size, mm, 4 msbits */
+dsp_size_mbsb:	.byte	msbs2(xsize,ysize)
+
+/* Horizontal border pixels (each side; total is twice this) */
+x_border:	.byte	0
+/* Vertical border lines (each side; total is twice this) */
+y_border:	.byte	0
+
+/* Bit 7 	Interlaced
+   Bits 6-5 	Stereo mode: 00=No stereo; other values depend on bit 0:
+   Bit 0=0: 01=Field sequential, sync=1 during right; 10=similar,
+     sync=1 during left; 11=4-way interleaved stereo
+   Bit 0=1 2-way interleaved stereo: 01=Right image on even lines;
+     10=Left image on even lines; 11=side-by-side
+   Bits 4-3 	Sync type: 00=Analog composite; 01=Bipolar analog composite;
+     10=Digital composite (on HSync); 11=Digital separate
+   Bit 2 	If digital separate: Vertical sync polarity (1=positive)
+   Other types: VSync serrated (HSync during VSync)
+   Bit 1 	If analog sync: Sync on all 3 RGB lines (else green only)
+   Digital: HSync polarity (1=positive)
+   Bit 0 	2-way line-interleaved stereo, if bits 4-3 are not 00. */
+features:	.byte	0x18+(VSYNC_POL<<2)+(HSYNC_POL<<1)
+
+descriptor2:	.byte	0,0	/* Not a detailed timing descriptor */
+		.byte	0	/* Must be zero */
+		.byte	0xff	/* Descriptor is monitor serial number (text) */
+		.byte	0	/* Must be zero */
+start1:		.ascii	"Linux #0"
+end1:		.byte	0x0a	/* End marker */
+		.fill	12-(end1-start1), 1, 0x20 /* Padded spaces */
+descriptor3:	.byte	0,0	/* Not a detailed timing descriptor */
+		.byte	0	/* Must be zero */
+		.byte	0xfd	/* Descriptor is monitor range limits */
+		.byte	0	/* Must be zero */
+start2:		.byte	VFREQ-1	/* Minimum vertical field rate (1-255 Hz) */
+		.byte	VFREQ+1	/* Maximum vertical field rate (1-255 Hz) */
+		.byte	(CLOCK/(XPIX+XBLANK))-1 /* Minimum horizontal line rate
+						    (1-255 kHz) */
+		.byte	(CLOCK/(XPIX+XBLANK))+1 /* Maximum horizontal line rate
+						    (1-255 kHz) */
+		.byte	(CLOCK/10000)+1	/* Maximum pixel clock rate, rounded up
+					   to 10 MHz multiple (10-2550 MHz) */
+		.byte	0	/* No extended timing information type */
+end2:		.byte	0x0a	/* End marker */
+		.fill	12-(end2-start2), 1, 0x20 /* Padded spaces */
+descriptor4:	.byte	0,0	/* Not a detailed timing descriptor */
+		.byte	0	/* Must be zero */
+		.byte	0xfc	/* Descriptor is text */
+		.byte	0	/* Must be zero */
+start3:		.ascii	TIMING_NAME
+end3:		.byte	0x0a	/* End marker */
+		.fill	12-(end3-start3), 1, 0x20 /* Padded spaces */
+extensions:	.byte	0	/* Number of extensions to follow */
+checksum:	.byte	CRC	/* Sum of all bytes must be 0 */

Documentation/EDID/hex

+"\t" 8/1 "0x%02x, " "\n"

Documentation/kernel-parameters.txt

@@ -713,6 +713,21 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			The filter can be disabled or changed to another
 			driver later using sysfs.
 
+	drm_kms_helper.edid_firmware=[<connector>:]<file>
+			Broken monitors, graphic adapters and KVMs may
+			send no or incorrect EDID data sets. This parameter
+			allows to specify an EDID data set in the
+			/lib/firmware directory that is used instead.
+			Generic built-in EDID data sets are used, if one of
+			edid/1024x768.bin, edid/1280x1024.bin,
+			edid/1680x1050.bin, or edid/1920x1080.bin is given
+			and no file with the same name exists. Details and
+			instructions how to build your own EDID data are
+			available in Documentation/EDID/HOWTO.txt. An EDID
+			data set will only be used for a particular connector,
+			if its name and a colon are prepended to the EDID
+			name.
+
 	dscc4.setup=	[NET]
 
 	earlycon=	[KNL] Output early console device and options.

drivers/gpu/drm/Kconfig

@@ -32,6 +32,18 @@ config DRM_KMS_HELPER
 	help
 	  FB and CRTC helpers for KMS drivers.
 
+config DRM_LOAD_EDID_FIRMWARE
+	bool "Allow to specify an EDID data set instead of probing for it"
+	depends on DRM_KMS_HELPER
+	help
+	  Say Y here, if you want to use EDID data to be loaded from the
+	  /lib/firmware directory or one of the provided built-in
+	  data sets. This may be necessary, if the graphics adapter or
+	  monitor are unable to provide appropriate EDID data. Since this
+	  feature is provided as a workaround for broken hardware, the
+	  default case is N. Details and instructions how to build your own
+	  EDID data are given in Documentation/EDID/HOWTO.txt.
+
 config DRM_TTM
 	tristate
 	depends on DRM

drivers/gpu/drm/Makefile

@@ -19,6 +19,7 @@ drm-$(CONFIG_COMPAT) += drm_ioc32.o
 drm-usb-y   := drm_usb.o
 
 drm_kms_helper-y := drm_fb_helper.o drm_crtc_helper.o drm_dp_i2c_helper.o
+drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
 
 obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
 

drivers/gpu/drm/drm_crtc_helper.c

@@ -37,6 +37,7 @@
 #include "drm_fourcc.h"
 #include "drm_crtc_helper.h"
 #include "drm_fb_helper.h"
+#include "drm_edid.h"
 
 static bool drm_kms_helper_poll = true;
 module_param_named(poll, drm_kms_helper_poll, bool, 0600);
@@ -118,7 +119,12 @@ int drm_helper_probe_single_connector_modes(struct drm_connector *connector,
 		goto prune;
 	}
 
-	count = (*connector_funcs->get_modes)(connector);
+#ifdef CONFIG_DRM_LOAD_EDID_FIRMWARE
+	count = drm_load_edid_firmware(connector);
+	if (count == 0)
+#endif
+		count = (*connector_funcs->get_modes)(connector);
+
 	if (count == 0 && connector->status == connector_status_connected)
 		count = drm_add_modes_noedid(connector, 1024, 768);
 	if (count == 0)

drivers/gpu/drm/drm_edid.c

@@ -149,8 +149,7 @@ EXPORT_SYMBOL(drm_edid_header_is_valid);
  * Sanity check the EDID block (base or extension).  Return 0 if the block
  * doesn't check out, or 1 if it's valid.
  */
-static bool
-drm_edid_block_valid(u8 *raw_edid)
+bool drm_edid_block_valid(u8 *raw_edid)
 {
 	int i;
 	u8 csum = 0;
@@ -203,6 +202,7 @@ drm_edid_block_valid(u8 *raw_edid)
 	}
 	return 0;
 }
+EXPORT_SYMBOL(drm_edid_block_valid);
 
 /**
  * drm_edid_is_valid - sanity check EDID data

drivers/gpu/drm/drm_edid_load.c

+/*
+   drm_edid_load.c: use a built-in EDID data set or load it via the firmware
+		    interface
+
+   Copyright (C) 2012 Carsten Emde <C.Emde@osadl.org>
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License
+   as published by the Free Software Foundation; either version 2
+   of the License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA.
+*/
+
+#include <linux/module.h>
+#include <linux/firmware.h>
+#include "drmP.h"
+#include "drm_crtc.h"
+#include "drm_crtc_helper.h"
+#include "drm_edid.h"
+
+static char edid_firmware[PATH_MAX];
+module_param_string(edid_firmware, edid_firmware, sizeof(edid_firmware), 0644);
+MODULE_PARM_DESC(edid_firmware, "Do not probe monitor, use specified EDID blob "
+	"from built-in data or /lib/firmware instead. ");
+
+#define GENERIC_EDIDS 4
+static char *generic_edid_name[GENERIC_EDIDS] = {
+	"edid/1024x768.bin",
+	"edid/1280x1024.bin",
+	"edid/1680x1050.bin",
+	"edid/1920x1080.bin",
+};
+
+static u8 generic_edid[GENERIC_EDIDS][128] = {
+	{
+	0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00,
+	0x31, 0xd8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x05, 0x16, 0x01, 0x03, 0x6d, 0x23, 0x1a, 0x78,
+	0xea, 0x5e, 0xc0, 0xa4, 0x59, 0x4a, 0x98, 0x25,
+	0x20, 0x50, 0x54, 0x00, 0x08, 0x00, 0x61, 0x40,
+	0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
+	0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x64, 0x19,
+	0x00, 0x40, 0x41, 0x00, 0x26, 0x30, 0x08, 0x90,
+	0x36, 0x00, 0x63, 0x0a, 0x11, 0x00, 0x00, 0x18,
+	0x00, 0x00, 0x00, 0xff, 0x00, 0x4c, 0x69, 0x6e,
+	0x75, 0x78, 0x20, 0x23, 0x30, 0x0a, 0x20, 0x20,
+	0x20, 0x20, 0x00, 0x00, 0x00, 0xfd, 0x00, 0x3b,
+	0x3d, 0x2f, 0x31, 0x07, 0x00, 0x0a, 0x20, 0x20,
+	0x20, 0x20, 0x20, 0x20, 0x00, 0x00, 0x00, 0xfc,
+	0x00, 0x4c, 0x69, 0x6e, 0x75, 0x78, 0x20, 0x58,
+	0x47, 0x41, 0x0a, 0x20, 0x20, 0x20, 0x00, 0x55,
+	},
+	{
+	0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00,
+	0x31, 0xd8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x05, 0x16, 0x01, 0x03, 0x6d, 0x2c, 0x23, 0x78,
+	0xea, 0x5e, 0xc0, 0xa4, 0x59, 0x4a, 0x98, 0x25,
+	0x20, 0x50, 0x54, 0x00, 0x00, 0x00, 0x81, 0x80,
+	0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
+	0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x30, 0x2a,
+	0x00, 0x98, 0x51, 0x00, 0x2a, 0x40, 0x30, 0x70,
+	0x13, 0x00, 0xbc, 0x63, 0x11, 0x00, 0x00, 0x1e,
+	0x00, 0x00, 0x00, 0xff, 0x00, 0x4c, 0x69, 0x6e,
+	0x75, 0x78, 0x20, 0x23, 0x30, 0x0a, 0x20, 0x20,
+	0x20, 0x20, 0x00, 0x00, 0x00, 0xfd, 0x00, 0x3b,
+	0x3d, 0x3e, 0x40, 0x0b, 0x00, 0x0a, 0x20, 0x20,
+	0x20, 0x20, 0x20, 0x20, 0x00, 0x00, 0x00, 0xfc,
+	0x00, 0x4c, 0x69, 0x6e, 0x75, 0x78, 0x20, 0x53,
+	0x58, 0x47, 0x41, 0x0a, 0x20, 0x20, 0x00, 0xa0,
+	},
+	{
+	0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00,
+	0x31, 0xd8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x05, 0x16, 0x01, 0x03, 0x6d, 0x2b, 0x1b, 0x78,
+	0xea, 0x5e, 0xc0, 0xa4, 0x59, 0x4a, 0x98, 0x25,
+	0x20, 0x50, 0x54, 0x00, 0x00, 0x00, 0xb3, 0x00,
+	0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
+	0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x21, 0x39,
+	0x90, 0x30, 0x62, 0x1a, 0x27, 0x40, 0x68, 0xb0,
+	0x36, 0x00, 0xb5, 0x11, 0x11, 0x00, 0x00, 0x1e,
+	0x00, 0x00, 0x00, 0xff, 0x00, 0x4c, 0x69, 0x6e,
+	0x75, 0x78, 0x20, 0x23, 0x30, 0x0a, 0x20, 0x20,
+	0x20, 0x20, 0x00, 0x00, 0x00, 0xfd, 0x00, 0x3b,
+	0x3d, 0x40, 0x42, 0x0f, 0x00, 0x0a, 0x20, 0x20,
+	0x20, 0x20, 0x20, 0x20, 0x00, 0x00, 0x00, 0xfc,
+	0x00, 0x4c, 0x69, 0x6e, 0x75, 0x78, 0x20, 0x57,
+	0x53, 0x58, 0x47, 0x41, 0x0a, 0x20, 0x00, 0x26,
+	},
+	{
+	0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00,
+	0x31, 0xd8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0x05, 0x16, 0x01, 0x03, 0x6d, 0x32, 0x1c, 0x78,
+	0xea, 0x5e, 0xc0, 0xa4, 0x59, 0x4a, 0x98, 0x25,
+	0x20, 0x50, 0x54, 0x00, 0x00, 0x00, 0xd1, 0xc0,
+	0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
+	0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x02, 0x3a,
+	0x80, 0x18, 0x71, 0x38, 0x2d, 0x40, 0x58, 0x2c,
+	0x45, 0x00, 0xf4, 0x19, 0x11, 0x00, 0x00, 0x1e,
+	0x00, 0x00, 0x00, 0xff, 0x00, 0x4c, 0x69, 0x6e,
+	0x75, 0x78, 0x20, 0x23, 0x30, 0x0a, 0x20, 0x20,
+	0x20, 0x20, 0x00, 0x00, 0x00, 0xfd, 0x00, 0x3b,
+	0x3d, 0x42, 0x44, 0x0f, 0x00, 0x0a, 0x20, 0x20,
+	0x20, 0x20, 0x20, 0x20, 0x00, 0x00, 0x00, 0xfc,
+	0x00, 0x4c, 0x69, 0x6e, 0x75, 0x78, 0x20, 0x46,
+	0x48, 0x44, 0x0a, 0x20, 0x20, 0x20, 0x00, 0x05,
+	},
+};
+
+static int edid_load(struct drm_connector *connector, char *name,
+		     char *connector_name)
+{
+	const struct firmware *fw;
+	struct platform_device *pdev;
+	u8 *fwdata = NULL, *edid;
+	int fwsize, expected;
+	int builtin = 0, err = 0;
+	int i, valid_extensions = 0;
+
+	pdev = platform_device_register_simple(connector_name, -1, NULL, 0);
+	if (IS_ERR(pdev)) {
+		DRM_ERROR("Failed to register EDID firmware platform device "
+		    "for connector \"%s\"\n", connector_name);
+		err = -EINVAL;
+		goto out;
+	}
+
+	err = request_firmware(&fw, name, &pdev->dev);
+	platform_device_unregister(pdev);
+
+	if (err) {
+		i = 0;
+		while (i < GENERIC_EDIDS && strcmp(name, generic_edid_name[i]))
+			i++;
+		if (i < GENERIC_EDIDS) {
+			err = 0;
+			builtin = 1;
+			fwdata = generic_edid[i];
+			fwsize = sizeof(generic_edid[i]);
+		}
+	}
+
+	if (err) {
+		DRM_ERROR("Requesting EDID firmware \"%s\" failed (err=%d)\n",
+		    name, err);
+		goto out;
+	}
+
+	if (fwdata == NULL) {
+		fwdata = (u8 *) fw->data;
+		fwsize = fw->size;
+	}
+
+	expected = (fwdata[0x7e] + 1) * EDID_LENGTH;
+	if (expected != fwsize) {
+		DRM_ERROR("Size of EDID firmware \"%s\" is invalid "
+		    "(expected %d, got %d)\n", name, expected, (int) fwsize);
+		err = -EINVAL;
+		goto relfw_out;
+	}
+
+	edid = kmalloc(fwsize, GFP_KERNEL);
+	if (edid == NULL) {
+		err = -ENOMEM;
+		goto relfw_out;
+	}
+	memcpy(edid, fwdata, fwsize);
+
+	if (!drm_edid_block_valid(edid)) {
+		DRM_ERROR("Base block of EDID firmware \"%s\" is invalid ",
+		    name);
+		kfree(edid);
+		err = -EINVAL;
+		goto relfw_out;
+	}
+
+	for (i = 1; i <= edid[0x7e]; i++) {
+		if (i != valid_extensions + 1)
+			memcpy(edid + (valid_extensions + 1) * EDID_LENGTH,
+			    edid + i * EDID_LENGTH, EDID_LENGTH);
+		if (drm_edid_block_valid(edid + i * EDID_LENGTH))
+			valid_extensions++;
+	}
+
+	if (valid_extensions != edid[0x7e]) {
+		edid[EDID_LENGTH-1] += edid[0x7e] - valid_extensions;
+		DRM_INFO("Found %d valid extensions instead of %d in EDID data "
+		    "\"%s\" for connector \"%s\"\n", valid_extensions,
+		    edid[0x7e], name, connector_name);
+		edid[0x7e] = valid_extensions;
+		edid = krealloc(edid, (valid_extensions + 1) * EDID_LENGTH,
+		    GFP_KERNEL);
+		if (edid == NULL) {
+			err = -ENOMEM;
+			goto relfw_out;
+		}
+	}
+
+	connector->display_info.raw_edid = edid;
+	DRM_INFO("Got %s EDID base block and %d extension%s from "
+	    "\"%s\" for connector \"%s\"\n", builtin ? "built-in" :
+	    "external", valid_extensions, valid_extensions == 1 ? "" : "s",
+	    name, connector_name);
+
+relfw_out:
+	release_firmware(fw);
+
+out:
+	return err;
+}
+
+int drm_load_edid_firmware(struct drm_connector *connector)
+{
+	char *connector_name = drm_get_connector_name(connector);
+	char *edidname = edid_firmware, *last, *colon;
+	int ret = 0;
+
+	if (*edidname == '\0')
+		return ret;
+
+	colon = strchr(edidname, ':');
+	if (colon != NULL) {
+		if (strncmp(connector_name, edidname, colon - edidname))
+			return ret;
+		edidname = colon + 1;
+		if (*edidname == '\0')
+			return ret;
+	}
+
+	last = edidname + strlen(edidname) - 1;
+	if (*last == '\n')
+		*last = '\0';
+
+	ret = edid_load(connector, edidname, connector_name);
+	if (ret)
+		return 0;
+
+	drm_mode_connector_update_edid_property(connector,
+	    (struct edid *) connector->display_info.raw_edid);
+
+	return drm_add_edid_modes(connector, (struct edid *)
+	    connector->display_info.raw_edid);
+}

include/drm/drm_crtc.h

@@ -1012,6 +1012,7 @@ extern int drm_add_modes_noedid(struct drm_connector *connector,
 				int hdisplay, int vdisplay);
 
 extern int drm_edid_header_is_valid(const u8 *raw_edid);
+extern bool drm_edid_block_valid(u8 *raw_edid);
 extern bool drm_edid_is_valid(struct edid *edid);
 struct drm_display_mode *drm_mode_find_dmt(struct drm_device *dev,
 					   int hsize, int vsize, int fresh);

include/drm/drm_edid.h

@@ -238,5 +238,6 @@ int drm_av_sync_delay(struct drm_connector *connector,
 		      struct drm_display_mode *mode);
 struct drm_connector *drm_select_eld(struct drm_encoder *encoder,
 				     struct drm_display_mode *mode);
+int drm_load_edid_firmware(struct drm_connector *connector);
 
 #endif /* __DRM_EDID_H__ */