Re: [PATCH] Preferred resolution detection for VBE

[Colin Watson <cjwatson@ubuntu.com>]

On Tue, Dec 14, 2010 at 04:38:36PM +0000, Colin Watson wrote:
> 2010-12-14  Colin Watson  <cjwatson@ubuntu.com>
> 
> 	Preferred resolution detection for VBE.

Updated version following comments from Vladimir on IRC.

2010-12-14  Colin Watson  <cjwatson@ubuntu.com>

	Preferred resolution detection for VBE.

	* grub-core/video/video.c (grub_video_edid_checksum): New function.
	(grub_video_get_edid): Likewise.
	(grub_video_edid_preferred_mode): Likewise.  Try EDID followed by
	the Flat Panel extension, in line with the X.org VESA driver.
	* grub-core/video/i386/pc/vbe.c (grub_vbe_bios_get_flat_panel_info):
	New function.
	(grub_vbe_bios_get_ddc_capabilities): Likewise.
	(grub_vbe_bios_read_edid): Likewise.
	(grub_vbe_get_preferred_mode): Likewise.
	(grub_video_vbe_setup): When the mode is "auto", try to get the
	preferred mode from VBE, and use the largest mode that is no larger
	than the preferred mode (some BIOSes expose a preferred mode that is
	not in their mode list!).  If this fails, fall back to 640x480 as a
	safe conservative choice.
	(grub_video_vbe_get_edid): New function.
	(grub_video_vbe_adapter): Add get_edid.
	* include/grub/video.h (struct grub_vbe_edid_info): New structure.
	(struct grub_video_adapter): Add get_edid.
	(grub_video_edid_checksum): Add prototype.
	(grub_video_get_edid): Likewise.
	(grub_video_edid_preferred_mode): Likewise.
	* include/grub/i386/pc/vbe.h (struct grub_vbe_flat_panel_info): New
	structure.
	(grub_vbe_bios_get_flat_panel_info): Add prototype.
	(grub_vbe_bios_get_ddc_capabilities): Likewise.
	(grub_vbe_bios_read_edid): Likewise.

	* grub-core/commands/videoinfo.c (print_edid): New function.
	(grub_cmd_videoinfo): Print EDID if available.

	* util/grub.d/00_header.in (GRUB_GFXMODE): Default to "auto".  This
	is more appropriate on a wider range of platforms than 640x480.

=== modified file 'grub-core/commands/videoinfo.c'
--- grub-core/commands/videoinfo.c	2010-09-15 12:37:28 +0000
+++ grub-core/commands/videoinfo.c	2010-12-14 17:59:42 +0000
@@ -77,6 +77,30 @@ hook (const struct grub_video_mode_info
   return 0;
 }
 
+static void
+print_edid (struct grub_video_edid_info *edid_info)
+{
+  unsigned int edid_width, edid_height;
+
+  if (grub_video_edid_checksum (edid_info))
+    {
+      grub_printf ("  EDID checksum invalid\n");
+      grub_errno = GRUB_ERR_NONE;
+      return;
+    }
+
+  grub_printf ("  EDID version: %u.%u\n",
+	       edid_info->version, edid_info->revision);
+  if (grub_video_edid_preferred_mode (edid_info, &edid_width, &edid_height)
+	== GRUB_ERR_NONE)
+    grub_printf ("    Preferred mode: %ux%u\n", edid_width, edid_height);
+  else
+    {
+      grub_printf ("    No preferred mode available\n");
+      grub_errno = GRUB_ERR_NONE;
+    }
+}
+
 static grub_err_t
 grub_cmd_videoinfo (grub_command_t cmd __attribute__ ((unused)),
 		    int argc, char **args)
@@ -120,6 +144,8 @@ grub_cmd_videoinfo (grub_command_t cmd _
 
   FOR_VIDEO_ADAPTERS (adapter)
   {
+    struct grub_video_edid_info edid_info;
+
     grub_printf ("Adapter '%s':\n", adapter->name);
 
     if (!adapter->iterate)
@@ -143,6 +169,11 @@ grub_cmd_videoinfo (grub_command_t cmd _
 
     adapter->iterate (hook);
 
+    if (adapter->get_edid (&edid_info) == GRUB_ERR_NONE)
+      print_edid (&edid_info);
+    else
+      grub_errno = GRUB_ERR_NONE;
+
     if (adapter->id != id)
       {
 	if (adapter->fini ())

=== modified file 'grub-core/video/i386/pc/vbe.c'
--- grub-core/video/i386/pc/vbe.c	2010-09-15 22:37:30 +0000
+++ grub-core/video/i386/pc/vbe.c	2010-12-14 17:31:20 +0000
@@ -273,6 +273,56 @@ grub_vbe_bios_get_pm_interface (grub_uin
   return regs.eax & 0xffff;
 }
 
+/* Call VESA BIOS 0x4f11 to get flat panel information, return status.  */
+grub_vbe_status_t
+grub_vbe_bios_get_flat_panel_info (struct grub_vbe_flat_panel_info *flat_panel_info)
+{
+  struct grub_bios_int_registers regs;
+
+  regs.eax = 0x4f11;
+  regs.ebx = 0x0001;
+  regs.es = (((grub_addr_t) flat_panel_info) & 0xffff0000) >> 4;
+  regs.edi = ((grub_addr_t) flat_panel_info) & 0xffff;
+  regs.flags = GRUB_CPU_INT_FLAGS_DEFAULT;
+  grub_bios_interrupt (0x10, &regs);
+  return regs.eax & 0xffff;
+}
+
+/* Call VESA BIOS 0x4f15 to get DDC availability, return status.  */
+grub_vbe_status_t
+grub_vbe_bios_get_ddc_capabilities (grub_uint8_t *level)
+{
+  struct grub_bios_int_registers regs;
+
+  regs.eax = 0x4f15;
+  regs.ebx = 0x0000;
+  regs.ecx = 0x0000;
+  regs.es = 0x0000;
+  regs.edi = 0x0000;
+  regs.flags = GRUB_CPU_INT_FLAGS_DEFAULT;
+  grub_bios_interrupt (0x10, &regs);
+
+  *level = regs.ebx & 0xff;
+  return regs.eax & 0xffff;
+}
+
+/* Call VESA BIOS 0x4f15 to read EDID information, return status.  */
+grub_vbe_status_t
+grub_vbe_bios_read_edid (struct grub_video_edid_info *edid_info)
+{
+  struct grub_bios_int_registers regs;
+
+  regs.eax = 0x4f15;
+  regs.ebx = 0x0001;
+  regs.ecx = 0x0000;
+  regs.edx = 0x0000;
+  regs.es = (((grub_addr_t) edid_info) & 0xffff0000) >> 4;
+  regs.edi = ((grub_addr_t) edid_info) & 0xffff;
+  regs.flags = GRUB_CPU_INT_FLAGS_DEFAULT;
+  grub_bios_interrupt (0x10, &regs);
+  return regs.eax & 0xffff;
+}
+
 
 grub_err_t
 grub_vbe_probe (struct grub_vbe_info_block *info_block)
@@ -327,6 +377,37 @@ grub_vbe_probe (struct grub_vbe_info_blo
   return GRUB_ERR_NONE;
 }
 
+static grub_err_t
+grub_vbe_get_preferred_mode (unsigned int *width, unsigned int *height)
+{
+  grub_vbe_status_t status;
+  grub_uint8_t ddc_level;
+  struct grub_video_edid_info edid_info;
+  struct grub_vbe_flat_panel_info flat_panel_info;
+
+  if (controller_info.version >= 0x200
+      && (grub_vbe_bios_get_ddc_capabilities (&ddc_level) & 0xff)
+	 == GRUB_VBE_STATUS_OK)
+    {
+      if (grub_video_get_edid (&edid_info) == GRUB_ERR_NONE
+	  && grub_video_edid_preferred_mode (&edid_info, width, height)
+	      == GRUB_ERR_NONE)
+	return GRUB_ERR_NONE;
+
+      grub_errno = GRUB_ERR_NONE;
+    }
+
+  status = grub_vbe_bios_get_flat_panel_info (&flat_panel_info);
+  if (status == GRUB_VBE_STATUS_OK)
+    {
+      *width = flat_panel_info.horizontal_size;
+      *height = flat_panel_info.vertical_size;
+      return GRUB_ERR_NONE;
+    }
+
+  return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "cannot get preferred mode");
+}
+
 grub_err_t
 grub_vbe_set_video_mode (grub_uint32_t vbe_mode,
 			 struct grub_vbe_mode_info_block *vbe_mode_info)
@@ -695,11 +776,28 @@ grub_video_vbe_setup (unsigned int width
   struct grub_vbe_mode_info_block best_vbe_mode_info;
   grub_uint32_t best_vbe_mode = 0;
   int depth;
+  int preferred_mode = 0;
 
   /* Decode depth from mode_type.  If it is zero, then autodetect.  */
   depth = (mode_type & GRUB_VIDEO_MODE_TYPE_DEPTH_MASK)
           >> GRUB_VIDEO_MODE_TYPE_DEPTH_POS;
 
+  if (width == 0 && height == 0)
+    {
+      grub_vbe_get_preferred_mode (&width, &height);
+      if (grub_errno == GRUB_ERR_NONE)
+	preferred_mode = 1;
+      else
+	{
+	  /* Fall back to 640x480.  This is conservative, but the largest
+	     mode supported by the graphics card may not be safe for the
+	     display device.  */
+	  grub_errno = GRUB_ERR_NONE;
+	  width = 640;
+	  height = 480;
+	}
+    }
+
   /* Walk thru mode list and try to find matching mode.  */
   for (p = vbe_mode_list; *p != 0xFFFF; p++)
     {
@@ -742,10 +840,21 @@ grub_video_vbe_setup (unsigned int width
 	/* Unsupported bitdepth . */
         continue;
 
-      if (((vbe_mode_info.x_resolution != width)
-	   || (vbe_mode_info.y_resolution != height)) && width != 0 && height != 0)
-        /* Non matching resolution.  */
-        continue;
+      if (preferred_mode)
+	{
+	  if (vbe_mode_info.x_resolution > width
+	      || vbe_mode_info.y_resolution > height)
+	    /* Resolution exceeds that of preferred mode.  */
+	    continue;
+	}
+      else
+	{
+	  if (((vbe_mode_info.x_resolution != width)
+	       || (vbe_mode_info.y_resolution != height))
+	      && width != 0 && height != 0)
+	    /* Non matching resolution.  */
+	    continue;
+	}
 
       /* Check if user requested RGB or index color mode.  */
       if ((mode_mask & GRUB_VIDEO_MODE_TYPE_COLOR_MASK) != 0)
@@ -855,6 +964,15 @@ grub_video_vbe_get_info_and_fini (struct
   return grub_video_fb_get_info_and_fini (mode_info, framebuf);
 }
 
+static grub_err_t
+grub_video_vbe_get_edid (struct grub_video_edid_info *edid_info)
+{
+  if (grub_vbe_bios_read_edid (edid_info) != GRUB_VBE_STATUS_OK)
+    return grub_error (GRUB_ERR_BAD_DEVICE, "EDID information not available");
+
+  return GRUB_ERR_NONE;
+}
+
 static void
 grub_video_vbe_print_adapter_specific_info (void)
 {
@@ -899,6 +1017,7 @@ static struct grub_video_adapter grub_vi
     .set_active_render_target = grub_video_fb_set_active_render_target,
     .get_active_render_target = grub_video_fb_get_active_render_target,
     .iterate = grub_video_vbe_iterate,
+    .get_edid = grub_video_vbe_get_edid,
     .print_adapter_specific_info = grub_video_vbe_print_adapter_specific_info,
 
     .next = 0

=== modified file 'grub-core/video/video.c'
--- grub-core/video/video.c	2010-06-24 19:22:40 +0000
+++ grub-core/video/video.c	2010-12-14 17:51:19 +0000
@@ -374,6 +374,68 @@ grub_video_get_active_render_target (str
   return grub_video_adapter_active->get_active_render_target (target);
 }
 
+grub_err_t
+grub_video_edid_checksum (struct grub_video_edid_info *edid_info)
+{
+  const char *edid_bytes = (const char *) edid_info;
+  int i;
+  char checksum = 0;
+
+  /* Check EDID checksum.  */
+  for (i = 0; i < 128; ++i)
+    checksum += edid_bytes[i];
+
+  if (checksum != 0)
+    return grub_error (GRUB_ERR_BAD_DEVICE,
+		       "invalid EDID checksum %d", checksum);
+
+  grub_errno = GRUB_ERR_NONE;
+  return grub_errno;
+}
+
+grub_err_t
+grub_video_get_edid (struct grub_video_edid_info *edid_info)
+{
+  if (! grub_video_adapter_active)
+    return grub_error (GRUB_ERR_BAD_DEVICE, "no video mode activated");
+
+  if (! grub_video_adapter_active->get_edid)
+    return grub_error (GRUB_ERR_BAD_DEVICE,
+		       "EDID information unavailable for this video mode");
+
+  if (grub_video_adapter_active->get_edid (edid_info) != GRUB_ERR_NONE)
+    return grub_errno;
+  if (grub_video_edid_checksum (edid_info) != GRUB_ERR_NONE)
+    return grub_errno;
+
+  return GRUB_ERR_NONE;
+}
+
+grub_err_t
+grub_video_edid_preferred_mode (struct grub_video_edid_info *edid_info,
+				unsigned int *width, unsigned int *height)
+{
+  /* Bit 1 in the Feature Support field indicates that the first
+     Detailed Timing Description is the preferred timing mode.  */
+  if (edid_info->version == 1 /* we don't understand later versions */
+      && (edid_info->feature_support
+	  & GRUB_VIDEO_EDID_FEATURE_PREFERRED_TIMING_MODE)
+      && edid_info->detailed_timings[0].pixel_clock)
+    {
+      *width = edid_info->detailed_timings[0].horizontal_active_lo
+	       | (((unsigned int)
+		   (edid_info->detailed_timings[0].horizontal_hi & 0xf0))
+		  << 4);
+      *height = edid_info->detailed_timings[0].vertical_active_lo
+		| (((unsigned int)
+		    (edid_info->detailed_timings[0].vertical_hi & 0xf0))
+		   << 4);
+      return GRUB_ERR_NONE;
+    }
+
+  return grub_error (GRUB_ERR_BAD_DEVICE, "no preferred mode available");
+}
+
 /* Parse <width>x<height>[x<depth>]*/
 static grub_err_t
 parse_modespec (const char *current_mode, int *width, int *height, int *depth)

=== modified file 'include/grub/i386/pc/vbe.h'
--- include/grub/i386/pc/vbe.h	2010-09-15 22:37:30 +0000
+++ include/grub/i386/pc/vbe.h	2010-12-14 17:03:13 +0000
@@ -19,6 +19,8 @@
 #ifndef GRUB_VBE_MACHINE_HEADER
 #define GRUB_VBE_MACHINE_HEADER	1
 
+#include <grub/video.h>
+
 /* Default video mode to be used.  */
 #define GRUB_VBE_DEFAULT_VIDEO_MODE     0x101
 
@@ -169,6 +171,21 @@ struct grub_vbe_palette_data
   grub_uint8_t alignment;
 } __attribute__ ((packed));
 
+struct grub_vbe_flat_panel_info
+{
+  grub_uint16_t horizontal_size;
+  grub_uint16_t vertical_size;
+  grub_uint16_t panel_type;
+  grub_uint8_t red_bpp;
+  grub_uint8_t green_bpp;
+  grub_uint8_t blue_bpp;
+  grub_uint8_t reserved_bpp;
+  grub_uint32_t reserved_offscreen_mem_size;
+  grub_vbe_farptr_t reserved_offscreen_mem_ptr;
+
+  grub_uint8_t reserved[14];
+} __attribute__ ((packed));
+
 /* Prototypes for helper functions.  */
 /* Call VESA BIOS 0x4f00 to get VBE Controller Information, return status.  */
 grub_vbe_status_t 
@@ -197,6 +214,15 @@ grub_vbe_bios_get_scanline_length (grub_
 grub_vbe_status_t 
 grub_vbe_bios_get_display_start (grub_uint32_t *x,
 				 grub_uint32_t *y);
+/* Call VESA BIOS 0x4f11 to get flat panel information, return status.  */
+grub_vbe_status_t
+grub_vbe_bios_get_flat_panel_info (struct grub_vbe_flat_panel_info *flat_panel_info);
+/* Call VESA BIOS 0x4f15 to get DDC availability, return status.  */
+grub_vbe_status_t
+grub_vbe_bios_get_ddc_capabilities (grub_uint8_t *level);
+/* Call VESA BIOS 0x4f15 to read EDID information, return status.  */
+grub_vbe_status_t
+grub_vbe_bios_read_edid (struct grub_video_edid_info *edid_data);
 
 grub_vbe_status_t grub_vbe_bios_getset_dac_palette_width (int set, int *width);
 

=== modified file 'include/grub/video.h'
--- include/grub/video.h	2010-12-10 16:45:58 +0000
+++ include/grub/video.h	2010-12-14 17:49:35 +0000
@@ -210,6 +210,66 @@ struct grub_video_palette_data
   grub_uint8_t a; /* Reserved bits value (0-255).  */
 };
 
+struct grub_video_edid_info
+{
+  grub_uint8_t header[8];
+  grub_uint16_t manufacturer_id;
+  grub_uint16_t product_id;
+  grub_uint32_t serial_number;
+  grub_uint8_t week_of_manufacture;
+  grub_uint8_t year_of_manufacture;
+  grub_uint8_t version;
+  grub_uint8_t revision;
+
+  grub_uint8_t video_input_definition;
+  grub_uint8_t max_horizontal_image_size;
+  grub_uint8_t max_vertical_image_size;
+  grub_uint8_t display_gamma;
+  grub_uint8_t feature_support;
+#define GRUB_VIDEO_EDID_FEATURE_PREFERRED_TIMING_MODE	(1 << 1)
+
+  grub_uint8_t red_green_lo;
+  grub_uint8_t blue_white_lo;
+  grub_uint8_t red_x_hi;
+  grub_uint8_t red_y_hi;
+  grub_uint8_t green_x_hi;
+  grub_uint8_t green_y_hi;
+  grub_uint8_t blue_x_hi;
+  grub_uint8_t blue_y_hi;
+  grub_uint8_t white_x_hi;
+  grub_uint8_t white_y_hi;
+
+  grub_uint8_t established_timings_1;
+  grub_uint8_t established_timings_2;
+  grub_uint8_t manufacturer_reserved_timings;
+
+  grub_uint16_t standard_timings[8];
+
+  struct {
+    grub_uint16_t pixel_clock;
+    /* Only valid if the pixel clock is non-null.  */
+    grub_uint8_t horizontal_active_lo;
+    grub_uint8_t horizontal_blanking_lo;
+    grub_uint8_t horizontal_hi;
+    grub_uint8_t vertical_active_lo;
+    grub_uint8_t vertical_blanking_lo;
+    grub_uint8_t vertical_hi;
+    grub_uint8_t horizontal_sync_offset_lo;
+    grub_uint8_t horizontal_sync_pulse_width_lo;
+    grub_uint8_t vertical_sync_lo;
+    grub_uint8_t sync_hi;
+    grub_uint8_t horizontal_image_size_lo;
+    grub_uint8_t vertical_image_size_lo;
+    grub_uint8_t image_size_hi;
+    grub_uint8_t horizontal_border;
+    grub_uint8_t vertical_border;
+    grub_uint8_t flags;
+  } detailed_timings[4];
+
+  grub_uint8_t extension_flag;
+  grub_uint8_t checksum;
+} __attribute__ ((packed));
+
 typedef enum grub_video_driver_id
   {
     GRUB_VIDEO_DRIVER_NONE,
@@ -311,6 +371,8 @@ struct grub_video_adapter
 
   int (*iterate) (int (*hook) (const struct grub_video_mode_info *info));
 
+  grub_err_t (*get_edid) (struct grub_video_edid_info *edid_info);
+
   void (*print_adapter_specific_info) (void);
 };
 typedef struct grub_video_adapter *grub_video_adapter_t;
@@ -423,6 +485,12 @@ grub_err_t EXPORT_FUNC (grub_video_set_a
 
 grub_err_t grub_video_get_active_render_target (struct grub_video_render_target **target);
 
+grub_err_t grub_video_edid_checksum (struct grub_video_edid_info *edid_info);
+grub_err_t grub_video_get_edid (struct grub_video_edid_info *edid_info);
+grub_err_t grub_video_edid_preferred_mode (struct grub_video_edid_info *edid_info,
+					   unsigned int *width,
+					   unsigned int *height);
+
 grub_err_t EXPORT_FUNC (grub_video_set_mode) (const char *modestring,
 					      unsigned int modemask,
 					      unsigned int modevalue);

=== modified file 'util/grub.d/00_header.in'
--- util/grub.d/00_header.in	2010-12-10 11:45:08 +0000
+++ util/grub.d/00_header.in	2010-12-14 16:20:51 +0000
@@ -36,7 +36,7 @@ done
 if [ "x${GRUB_DEFAULT}" = "x" ] ; then GRUB_DEFAULT=0 ; fi
 if [ "x${GRUB_DEFAULT}" = "xsaved" ] ; then GRUB_DEFAULT='${saved_entry}' ; fi
 if [ "x${GRUB_TIMEOUT}" = "x" ] ; then GRUB_TIMEOUT=5 ; fi
-if [ "x${GRUB_GFXMODE}" = "x" ] ; then GRUB_GFXMODE=640x480 ; fi
+if [ "x${GRUB_GFXMODE}" = "x" ] ; then GRUB_GFXMODE=auto ; fi
 
 if [ "x${GRUB_DEFAULT_BUTTON}" = "x" ] ; then GRUB_DEFAULT_BUTTON="$GRUB_DEFAULT" ; fi
 if [ "x${GRUB_DEFAULT_BUTTON}" = "xsaved" ] ; then GRUB_DEFAULT_BUTTON='${saved_entry}' ; fi

-- 
Colin Watson                                       [cjwatson@ubuntu.com]