MonitorXrandr: implement correct EDID parsing

To provide valid values for the vendor, product and serial fields
we need to read the EDID and parse it.
Parser kindly provided by gnome-desktop.

https://bugzilla.gnome.org/show_bug.cgi?id=705670

4 files changed, 835 insertions, 64 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 5d1261552..6d40300e4 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -95,6 +95,8 @@ libmutter_la_SOURCES =				\
 	ui/draw-workspace.h			\
 	core/edge-resistance.c			\
 	core/edge-resistance.h			\
+	core/edid-parse.c			\
+	core/edid.h				\
 	core/errors.c				\
 	meta/errors.h				\
 	core/frame.c				\
diff --git a/src/core/edid-parse.c b/src/core/edid-parse.c
new file mode 100644
index 000000000..5b3283ae5
--- /dev/null
+++ b/src/core/edid-parse.c
@@ -0,0 +1,539 @@
+/*
+ * Copyright 2007 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * on the rights to use, copy, modify, merge, publish, distribute, sub
+ * license, and/or sell copies of the Software, and to permit persons to whom
+ * the Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+/* Author: Soren Sandmann <sandmann@redhat.com> */
+
+#include "edid.h"
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include <glib.h>
+
+static int
+get_bit (int in, int bit)
+{
+  return (in & (1 << bit)) >> bit;
+}
+
+static int
+get_bits (int in, int begin, int end)
+{
+  int mask = (1 << (end - begin + 1)) - 1;
+
+  return (in >> begin) & mask;
+}
+
+static int
+decode_header (const uchar *edid)
+{
+  if (memcmp (edid, "\x00\xff\xff\xff\xff\xff\xff\x00", 8) == 0)
+    return TRUE;
+  return FALSE;
+}
+
+static int
+decode_vendor_and_product_identification (const uchar *edid, MonitorInfo *info)
+{
+  int is_model_year;
+
+  /* Manufacturer Code */
+  info->manufacturer_code[0]  = get_bits (edid[0x08], 2, 6);
+  info->manufacturer_code[1]  = get_bits (edid[0x08], 0, 1) << 3;
+  info->manufacturer_code[1] |= get_bits (edid[0x09], 5, 7);
+  info->manufacturer_code[2]  = get_bits (edid[0x09], 0, 4);
+  info->manufacturer_code[3]  = '\0';
+
+  info->manufacturer_code[0] += 'A' - 1;
+  info->manufacturer_code[1] += 'A' - 1;
+  info->manufacturer_code[2] += 'A' - 1;
+
+  /* Product Code */
+  info->product_code = edid[0x0b] << 8 | edid[0x0a];
+
+  /* Serial Number */
+  info->serial_number =
+    edid[0x0c] | edid[0x0d] << 8 | edid[0x0e] << 16 | edid[0x0f] << 24;
+
+  /* Week and Year */
+  is_model_year = FALSE;
+  switch (edid[0x10])
+    {
+    case 0x00:
+      info->production_week = -1;
+      break;
+
+    case 0xff:
+      info->production_week = -1;
+      is_model_year = TRUE;
+      break;
+
+    default:
+      info->production_week = edid[0x10];
+      break;
+    }
+
+  if (is_model_year)
+    {
+      info->production_year = -1;
+      info->model_year = 1990 + edid[0x11];
+    }
+  else
+    {
+      info->production_year = 1990 + edid[0x11];
+      info->model_year = -1;
+    }
+
+  return TRUE;
+}
+
+static int
+decode_edid_version (const uchar *edid, MonitorInfo *info)
+{
+  info->major_version = edid[0x12];
+  info->minor_version = edid[0x13];
+
+  return TRUE;
+}
+
+static int
+decode_display_parameters (const uchar *edid, MonitorInfo *info)
+{
+  /* Digital vs Analog */
+  info->is_digital = get_bit (edid[0x14], 7);
+
+  if (info->is_digital)
+    {
+      int bits;
+
+      static const int bit_depth[8] =
+        {
+          -1, 6, 8, 10, 12, 14, 16, -1
+        };
+
+      static const Interface interfaces[6] =
+        {
+          UNDEFINED, DVI, HDMI_A, HDMI_B, MDDI, DISPLAY_PORT
+        };
+
+      bits = get_bits (edid[0x14], 4, 6);
+      info->connector.digital.bits_per_primary = bit_depth[bits];
+
+      bits = get_bits (edid[0x14], 0, 3);
+
+      if (bits <= 5)
+        info->connector.digital.interface = interfaces[bits];
+      else
+        info->connector.digital.interface = UNDEFINED;
+    }
+  else
+    {
+      int bits = get_bits (edid[0x14], 5, 6);
+
+      static const double levels[][3] =
+        {
+          { 0.7,   0.3,    1.0 },
+          { 0.714, 0.286,  1.0 },
+          { 1.0,   0.4,    1.4 },
+          { 0.7,   0.0,    0.7 },
+        };
+
+      info->connector.analog.video_signal_level = levels[bits][0];
+      info->connector.analog.sync_signal_level = levels[bits][1];
+      info->connector.analog.total_signal_level = levels[bits][2];
+
+      info->connector.analog.blank_to_black = get_bit (edid[0x14], 4);
+
+      info->connector.analog.separate_hv_sync = get_bit (edid[0x14], 3);
+      info->connector.analog.composite_sync_on_h = get_bit (edid[0x14], 2);
+      info->connector.analog.composite_sync_on_green = get_bit (edid[0x14], 1);
+
+      info->connector.analog.serration_on_vsync = get_bit (edid[0x14], 0);
+    }
+
+  /* Screen Size / Aspect Ratio */
+  if (edid[0x15] == 0 && edid[0x16] == 0)
+    {
+      info->width_mm = -1;
+      info->height_mm = -1;
+      info->aspect_ratio = -1.0;
+    }
+  else if (edid[0x16] == 0)
+    {
+      info->width_mm = -1;
+      info->height_mm = -1; 
+      info->aspect_ratio = 100.0 / (edid[0x15] + 99);
+    }
+  else if (edid[0x15] == 0)
+    {
+      info->width_mm = -1;
+      info->height_mm = -1;
+      info->aspect_ratio = 100.0 / (edid[0x16] + 99);
+      info->aspect_ratio = 1/info->aspect_ratio; /* portrait */
+    }
+  else
+    {
+      info->width_mm = 10 * edid[0x15];
+      info->height_mm = 10 * edid[0x16];
+    }
+
+  /* Gamma */
+  if (edid[0x17] == 0xFF)
+    info->gamma = -1.0;
+  else
+    info->gamma = (edid[0x17] + 100.0) / 100.0;
+
+  /* Features */
+  info->standby = get_bit (edid[0x18], 7);
+  info->suspend = get_bit (edid[0x18], 6);
+  info->active_off = get_bit (edid[0x18], 5);
+
+  if (info->is_digital)
+    {
+      info->connector.digital.rgb444 = TRUE;
+      if (get_bit (edid[0x18], 3))
+        info->connector.digital.ycrcb444 = 1;
+      if (get_bit (edid[0x18], 4))
+        info->connector.digital.ycrcb422 = 1;
+    }
+  else
+    {
+      int bits = get_bits (edid[0x18], 3, 4);
+      ColorType color_type[4] =
+        {
+          MONOCHROME, RGB, OTHER_COLOR, UNDEFINED_COLOR
+        };
+
+      info->connector.analog.color_type = color_type[bits];
+    }
+
+  info->srgb_is_standard = get_bit (edid[0x18], 2);
+
+  /* In 1.3 this is called "has preferred timing" */
+  info->preferred_timing_includes_native = get_bit (edid[0x18], 1);
+
+  /* FIXME: In 1.3 this indicates whether the monitor accepts GTF */
+  info->continuous_frequency = get_bit (edid[0x18], 0);
+  return TRUE;
+}
+
+static double
+decode_fraction (int high, int low)
+{
+  double result = 0.0;
+  int i;
+
+  high = (high << 2) | low;
+
+  for (i = 0; i < 10; ++i)
+    result += get_bit (high, i) * pow (2, i - 10);
+
+  return result;
+}
+
+static int
+decode_color_characteristics (const uchar *edid, MonitorInfo *info)
+{
+  info->red_x = decode_fraction (edid[0x1b], get_bits (edid[0x19], 6, 7));
+  info->red_y = decode_fraction (edid[0x1c], get_bits (edid[0x19], 5, 4));
+  info->green_x = decode_fraction (edid[0x1d], get_bits (edid[0x19], 2, 3));
+  info->green_y = decode_fraction (edid[0x1e], get_bits (edid[0x19], 0, 1));
+  info->blue_x = decode_fraction (edid[0x1f], get_bits (edid[0x1a], 6, 7));
+  info->blue_y = decode_fraction (edid[0x20], get_bits (edid[0x1a], 4, 5));
+  info->white_x = decode_fraction (edid[0x21], get_bits (edid[0x1a], 2, 3));
+  info->white_y = decode_fraction (edid[0x22], get_bits (edid[0x1a], 0, 1));
+
+  return TRUE;
+}
+
+static int
+decode_established_timings (const uchar *edid, MonitorInfo *info)
+{
+  static const Timing established[][8] = 
+    {
+      {
+        { 800, 600, 60 },
+        { 800, 600, 56 },
+        { 640, 480, 75 },
+        { 640, 480, 72 },
+        { 640, 480, 67 },
+        { 640, 480, 60 },
+        { 720, 400, 88 },
+        { 720, 400, 70 }
+      },
+      {
+        { 1280, 1024, 75 },
+        { 1024, 768, 75 },
+        { 1024, 768, 70 },
+        { 1024, 768, 60 },
+        { 1024, 768, 87 },
+        { 832, 624, 75 },
+        { 800, 600, 75 },
+        { 800, 600, 72 }
+	},
+      {
+        { 0, 0, 0 },
+        { 0, 0, 0 },
+        { 0, 0, 0 },
+        { 0, 0, 0 },
+        { 0, 0, 0 },
+        { 0, 0, 0 },
+        { 0, 0, 0 },
+        { 1152, 870, 75 }
+      },
+    };
+
+  int i, j, idx;
+
+  idx = 0;
+  for (i = 0; i < 3; ++i)
+    {
+      for (j = 0; j < 8; ++j)
+	{
+          int byte = edid[0x23 + i];
+
+          if (get_bit (byte, j) && established[i][j].frequency != 0)
+            info->established[idx++] = established[i][j];
+	}
+    }
+  return TRUE;
+}
+
+static int
+decode_standard_timings (const uchar *edid, MonitorInfo *info)
+{
+  int i;
+
+  for (i = 0; i < 8; i++)
+    {
+      int first = edid[0x26 + 2 * i];
+      int second = edid[0x27 + 2 * i];
+
+      if (first != 0x01 && second != 0x01)
+	{
+          int w = 8 * (first + 31);
+          int h = 0;
+
+          switch (get_bits (second, 6, 7))
+            {
+	    case 0x00: h = (w / 16) * 10; break;
+	    case 0x01: h = (w / 4) * 3; break;
+	    case 0x02: h = (w / 5) * 4; break;
+	    case 0x03: h = (w / 16) * 9; break;
+	    }
+
+          info->standard[i].width = w;
+          info->standard[i].height = h;
+          info->standard[i].frequency = get_bits (second, 0, 5) + 60;
+	}
+    }
+
+  return TRUE;
+}
+
+static void
+decode_lf_string (const uchar *s, int n_chars, char *result)
+{
+  int i;
+  for (i = 0; i < n_chars; ++i)
+    {
+      if (s[i] == 0x0a)
+	{
+          *result++ = '\0';
+          break;
+	}
+      else if (s[i] == 0x00)
+	{
+          /* Convert embedded 0's to spaces */
+          *result++ = ' ';
+	}
+      else
+	{
+          *result++ = s[i];
+	}
+    }
+}
+
+static void
+decode_display_descriptor (const uchar *desc,
+			   MonitorInfo *info)
+{
+  switch (desc[0x03])
+    {
+    case 0xFC:
+      decode_lf_string (desc + 5, 13, info->dsc_product_name);
+      break;
+    case 0xFF:
+      decode_lf_string (desc + 5, 13, info->dsc_serial_number);
+      break;
+    case 0xFE:
+      decode_lf_string (desc + 5, 13, info->dsc_string);
+      break;
+    case 0xFD:
+      /* Range Limits */
+      break;
+    case 0xFB:
+      /* Color Point */
+      break;
+    case 0xFA:
+      /* Timing Identifications */
+      break;
+    case 0xF9:
+      /* Color Management */
+      break;
+    case 0xF8:
+      /* Timing Codes */
+      break;
+    case 0xF7:
+      /* Established Timings */
+      break;
+    case 0x10:
+      break;
+    }
+}
+
+static void
+decode_detailed_timing (const uchar *timing,
+			DetailedTiming *detailed)
+{
+  int bits;
+  StereoType stereo[] =
+    {
+      NO_STEREO, NO_STEREO, FIELD_RIGHT, FIELD_LEFT,
+      TWO_WAY_RIGHT_ON_EVEN, TWO_WAY_LEFT_ON_EVEN,
+      FOUR_WAY_INTERLEAVED, SIDE_BY_SIDE
+    };
+
+  detailed->pixel_clock = (timing[0x00] | timing[0x01] << 8) * 10000;
+  detailed->h_addr = timing[0x02] | ((timing[0x04] & 0xf0) << 4);
+  detailed->h_blank = timing[0x03] | ((timing[0x04] & 0x0f) << 8);
+  detailed->v_addr = timing[0x05] | ((timing[0x07] & 0xf0) << 4);
+  detailed->v_blank = timing[0x06] | ((timing[0x07] & 0x0f) << 8);
+  detailed->h_front_porch = timing[0x08] | get_bits (timing[0x0b], 6, 7) << 8;
+  detailed->h_sync = timing[0x09] | get_bits (timing[0x0b], 4, 5) << 8;
+  detailed->v_front_porch =
+    get_bits (timing[0x0a], 4, 7) | get_bits (timing[0x0b], 2, 3) << 4;
+  detailed->v_sync =
+    get_bits (timing[0x0a], 0, 3) | get_bits (timing[0x0b], 0, 1) << 4;
+  detailed->width_mm =  timing[0x0c] | get_bits (timing[0x0e], 4, 7) << 8;
+  detailed->height_mm = timing[0x0d] | get_bits (timing[0x0e], 0, 3) << 8;
+  detailed->right_border = timing[0x0f];
+  detailed->top_border = timing[0x10];
+
+  detailed->interlaced = get_bit (timing[0x11], 7);
+
+  /* Stereo */
+  bits = get_bits (timing[0x11], 5, 6) << 1 | get_bit (timing[0x11], 0);
+  detailed->stereo = stereo[bits];
+
+  /* Sync */
+  bits = timing[0x11];
+
+  detailed->digital_sync = get_bit (bits, 4);
+  if (detailed->digital_sync)
+    {
+      detailed->connector.digital.composite = !get_bit (bits, 3);
+
+      if (detailed->connector.digital.composite)
+	{
+          detailed->connector.digital.serrations = get_bit (bits, 2);
+          detailed->connector.digital.negative_vsync = FALSE;
+	}
+      else
+	{
+          detailed->connector.digital.serrations = FALSE;
+          detailed->connector.digital.negative_vsync = !get_bit (bits, 2);
+	}
+
+      detailed->connector.digital.negative_hsync = !get_bit (bits, 0);
+    }
+  else
+    {
+      detailed->connector.analog.bipolar = get_bit (bits, 3);
+      detailed->connector.analog.serrations = get_bit (bits, 2);
+      detailed->connector.analog.sync_on_green = !get_bit (bits, 1);
+    }
+}
+
+static int
+decode_descriptors (const uchar *edid, MonitorInfo *info)
+{
+  int i;
+  int timing_idx;
+
+  timing_idx = 0;
+
+  for (i = 0; i < 4; ++i)
+    {
+      int index = 0x36 + i * 18;
+
+      if (edid[index + 0] == 0x00 && edid[index + 1] == 0x00)
+	{
+          decode_display_descriptor (edid + index, info);
+	}
+      else
+	{
+          decode_detailed_timing (edid + index, &(info->detailed_timings[timing_idx++]));
+	}
+    }
+
+  info->n_detailed_timings = timing_idx;
+
+  return TRUE;
+}
+
+static void
+decode_check_sum (const uchar *edid,
+		  MonitorInfo *info)
+{
+  int i;
+  uchar check = 0;
+
+  for (i = 0; i < 128; ++i)
+    check += edid[i];
+
+  info->checksum = check;
+}
+
+MonitorInfo *
+decode_edid (const uchar *edid)
+{
+  MonitorInfo *info = g_new0 (MonitorInfo, 1);
+
+  decode_check_sum (edid, info);
+
+  if (decode_header (edid)
+      && decode_vendor_and_product_identification (edid, info)
+      && decode_edid_version (edid, info)
+      && decode_display_parameters (edid, info)
+      && decode_color_characteristics (edid, info)
+      && decode_established_timings (edid, info)
+      && decode_standard_timings (edid, info)
+      && decode_descriptors (edid, info))
+    {
+      return info;
+    }
+  else
+    {
+      g_free (info);
+      return NULL;
+    }
+}
diff --git a/src/core/edid.h b/src/core/edid.h
new file mode 100644
index 000000000..703c639ee
--- /dev/null
+++ b/src/core/edid.h
@@ -0,0 +1,195 @@
+/* edid.h
+ *
+ * Copyright 2007, 2008, Red Hat, Inc.
+ * 
+ * This file is part of the Gnome Library.
+ * 
+ * The Gnome Library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * The Gnome Library 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
+ * Library General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Library General Public
+ * License along with the Gnome Library; see the file COPYING.LIB.  If not,
+ * write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ * 
+ * Author: Soren Sandmann <sandmann@redhat.com>
+ */
+
+#ifndef EDID_H
+#define EDID_H
+
+typedef unsigned char uchar;
+typedef struct MonitorInfo MonitorInfo;
+typedef struct Timing Timing;
+typedef struct DetailedTiming DetailedTiming;
+
+typedef enum
+{
+  UNDEFINED,
+  DVI,
+  HDMI_A,
+  HDMI_B,
+  MDDI,
+  DISPLAY_PORT
+} Interface;
+
+typedef enum
+{
+  UNDEFINED_COLOR,
+  MONOCHROME,
+  RGB,
+  OTHER_COLOR
+} ColorType;
+
+typedef enum
+{
+  NO_STEREO,
+  FIELD_RIGHT,
+  FIELD_LEFT,
+  TWO_WAY_RIGHT_ON_EVEN,
+  TWO_WAY_LEFT_ON_EVEN,
+  FOUR_WAY_INTERLEAVED,
+  SIDE_BY_SIDE
+} StereoType;
+
+struct Timing
+{
+  int width;
+  int height;
+  int frequency;
+};
+
+struct DetailedTiming
+{
+  int		pixel_clock;
+  int		h_addr;
+  int		h_blank;
+  int		h_sync;
+  int		h_front_porch;
+  int		v_addr;
+  int		v_blank;
+  int		v_sync;
+  int		v_front_porch;
+  int		width_mm;
+  int		height_mm;
+  int		right_border;
+  int		top_border;
+  int		interlaced;
+  StereoType	stereo;
+
+  int		digital_sync;
+  union
+  {
+    struct
+    {
+      int bipolar;
+      int serrations;
+      int sync_on_green;
+    } analog;
+
+    struct
+    {
+      int composite;
+      int serrations;
+      int negative_vsync;
+      int negative_hsync;
+    } digital;
+  } connector;
+};
+
+struct MonitorInfo
+{
+  int		checksum;
+  char		manufacturer_code[4];
+  int		product_code;
+  unsigned int	serial_number;
+
+  int		production_week;	/* -1 if not specified */
+  int		production_year;	/* -1 if not specified */
+  int		model_year;		/* -1 if not specified */
+
+  int		major_version;
+  int		minor_version;
+
+  int		is_digital;
+
+  union
+  {
+    struct
+    {
+      int	bits_per_primary;
+      Interface	interface;
+      int	rgb444;
+      int	ycrcb444;
+      int	ycrcb422;
+    } digital;
+
+    struct
+    {
+      double	video_signal_level;
+      double	sync_signal_level;
+      double	total_signal_level;
+
+      int	blank_to_black;
+
+      int	separate_hv_sync;
+      int	composite_sync_on_h;
+      int	composite_sync_on_green;
+      int	serration_on_vsync;
+      ColorType	color_type;
+    } analog;
+  } connector;
+
+  int		width_mm;		/* -1 if not specified */
+  int		height_mm;		/* -1 if not specified */
+  double	aspect_ratio;		/* -1.0 if not specififed */
+
+  double	gamma;			/* -1.0 if not specified */
+
+  int		standby;
+  int		suspend;
+  int		active_off;
+
+  int		srgb_is_standard;
+  int		preferred_timing_includes_native;
+  int		continuous_frequency;
+
+  double	red_x;
+  double	red_y;
+  double	green_x;
+  double	green_y;
+  double	blue_x;
+  double	blue_y;
+  double	white_x;
+  double	white_y;
+
+  Timing	established[24];	/* Terminated by 0x0x0 */
+  Timing	standard[8];
+
+  int		n_detailed_timings;
+  DetailedTiming detailed_timings[4];	/* If monitor has a preferred
+                                         * mode, it is the first one
+                                         * (whether it has, is
+                                         * determined by the 
+                                         * preferred_timing_includes
+                                         * bit.
+                                         */
+
+  /* Optional product description */
+  char		dsc_serial_number[14];
+  char		dsc_product_name[14];
+  char		dsc_string[14];		/* Unspecified ASCII data */
+};
+
+MonitorInfo *decode_edid (const uchar *data);
+char *make_display_name (const MonitorInfo *info);
+char *make_display_size_string (int width_mm, int height_mm);
+
+#endif
diff --git a/src/core/monitor-xrandr.c b/src/core/monitor-xrandr.c
index e8cc6e95e..c8e189ef7 100644
--- a/src/core/monitor-xrandr.c
+++ b/src/core/monitor-xrandr.c
@@ -40,6 +40,8 @@
 #include <meta/errors.h>
 #include "monitor-private.h"
 
+#include "edid.h"
+
 #define ALL_WL_TRANSFORMS ((1 << (WL_OUTPUT_TRANSFORM_FLIPPED_270 + 1)) - 1)
 
 struct _MetaMonitorManagerXrandr
@@ -236,6 +238,74 @@ compare_outputs (const void *one,
   return strcmp (o_one->name, o_two->name);
 }
 
+static guint8 *
+get_edid_property (Display  *dpy,
+                   RROutput  output,
+                   Atom      atom,
+                   gsize    *len)
+{
+  unsigned char *prop;
+  int actual_format;
+  unsigned long nitems, bytes_after;
+  Atom actual_type;
+  guint8 *result;
+
+  XRRGetOutputProperty (dpy, output, atom,
+                        0, 100, False, False,
+                        AnyPropertyType,
+                        &actual_type, &actual_format,
+                        &nitems, &bytes_after, &prop);
+
+  if (actual_type == XA_INTEGER && actual_format == 8)
+    {
+      result = g_memdup (prop, nitems);
+      if (len)
+        *len = nitems;
+    }
+  else
+    {
+      result = NULL;
+    }
+
+  XFree (prop);
+    
+  return result;
+}
+
+static GBytes *
+read_output_edid (MetaMonitorManagerXrandr *manager_xrandr,
+                  XID                       output_id)
+{
+  Atom edid_atom;
+  guint8 *result;
+  gsize len;
+
+  edid_atom = XInternAtom (manager_xrandr->xdisplay, "EDID", FALSE);
+  result = get_edid_property (manager_xrandr->xdisplay, output_id, edid_atom, &len);
+
+  if (!result)
+    {
+      edid_atom = XInternAtom (manager_xrandr->xdisplay, "EDID_DATA", FALSE);
+      result = get_edid_property (manager_xrandr->xdisplay, output_id, edid_atom, &len);
+    }
+
+  if (!result)
+    {
+      edid_atom = XInternAtom (manager_xrandr->xdisplay, "XFree86_DDC_EDID1_RAWDATA", FALSE);
+      result = get_edid_property (manager_xrandr->xdisplay, output_id, edid_atom, &len);
+    }
+
+  if (result)
+    {
+      if (len > 0 && len % 128 == 0)
+        return g_bytes_new_take (result, len);
+      else
+        g_free (result);
+    }
+
+  return NULL;
+}
+
 static void
 meta_monitor_manager_xrandr_read_current (MetaMonitorManager *manager)
 {
@@ -365,11 +435,36 @@ meta_monitor_manager_xrandr_read_current (MetaMonitorManager *manager)
 
       if (output->connection != RR_Disconnected)
 	{
+          GBytes *edid;
+          MonitorInfo *parsed_edid;
+
 	  meta_output->output_id = resources->outputs[i];
 	  meta_output->name = g_strdup (output->name);
-	  meta_output->vendor = g_strdup ("unknown");
-	  meta_output->product = g_strdup ("unknown");
-	  meta_output->serial = g_strdup ("");
+
+          edid = read_output_edid (manager_xrandr, meta_output->output_id);
+          if (edid)
+            {
+              gsize len;
+
+              parsed_edid = decode_edid (g_bytes_get_data (edid, &len));
+              if (parsed_edid)
+                {
+                  meta_output->vendor = g_strndup (parsed_edid->manufacturer_code, 4);
+                  meta_output->product = g_strndup (parsed_edid->dsc_product_name, 14);
+                  meta_output->serial = g_strndup (parsed_edid->dsc_serial_number, 14);
+
+                  g_free (parsed_edid);
+                }
+
+              g_bytes_unref (edid);
+            }
+
+          if (!meta_output->vendor)
+            {
+              meta_output->vendor = g_strdup ("unknown");
+              meta_output->product = g_strdup ("unknown");
+              meta_output->serial = g_strdup ("unknown");
+            }
 	  meta_output->width_mm = output->mm_width;
 	  meta_output->height_mm = output->mm_height;
 	  meta_output->subpixel_order = COGL_SUBPIXEL_ORDER_UNKNOWN;
@@ -467,73 +562,13 @@ meta_monitor_manager_xrandr_read_current (MetaMonitorManager *manager)
     }
 }
 
-static guint8 *
-get_edid_property (Display  *dpy,
-                   RROutput  output,
-                   Atom      atom,
-                   gsize    *len)
-{
-  unsigned char *prop;
-  int actual_format;
-  unsigned long nitems, bytes_after;
-  Atom actual_type;
-  guint8 *result;
-
-  XRRGetOutputProperty (dpy, output, atom,
-                        0, 100, False, False,
-                        AnyPropertyType,
-                        &actual_type, &actual_format,
-                        &nitems, &bytes_after, &prop);
-
-  if (actual_type == XA_INTEGER && actual_format == 8)
-    {
-      result = g_memdup (prop, nitems);
-      if (len)
-        *len = nitems;
-    }
-  else
-    {
-      result = NULL;
-    }
-
-  XFree (prop);
-    
-  return result;
-}
-
 static GBytes *
 meta_monitor_manager_xrandr_read_edid (MetaMonitorManager *manager,
                                        MetaOutput         *output)
 {
   MetaMonitorManagerXrandr *manager_xrandr = META_MONITOR_MANAGER_XRANDR (manager);
-  Atom edid_atom;
-  guint8 *result;
-  gsize len;
-
-  edid_atom = XInternAtom (manager_xrandr->xdisplay, "EDID", FALSE);
-  result = get_edid_property (manager_xrandr->xdisplay, output->output_id, edid_atom, &len);
 
-  if (!result)
-    {
-      edid_atom = XInternAtom (manager_xrandr->xdisplay, "EDID_DATA", FALSE);
-      result = get_edid_property (manager_xrandr->xdisplay, output->output_id, edid_atom, &len);
-    }
-
-  if (!result)
-    {
-      edid_atom = XInternAtom (manager_xrandr->xdisplay, "XFree86_DDC_EDID1_RAWDATA", FALSE);
-      result = get_edid_property (manager_xrandr->xdisplay, output->output_id, edid_atom, &len);
-    }
-
-  if (result)
-    {
-      if (len > 0 && len % 128 == 0)
-        return g_bytes_new_take (result, len);
-      else
-        g_free (result);
-    }
-
-  return NULL;
+  return read_output_edid (manager_xrandr, output->output_id);
 }
 
 static void