loader/i386/linux: Transfer EDID information to kernel

The Linux kernel's struct bootparams provides a field at offset 0x140
for storing an EDID header. Copy the video adapter's data to the field.

The edid_info field was added in 2003 (see "[FBDEV] EDID support from
OpenFirmware on PPC platoforms and from the BIOS on intel platforms."),
but only got useable in 2004 (see "[PATCH] Fix EDID_INFO in zero-page").
The boot protocol was at version 2.03 at that time.

The field was never used much, but with the recent addition of the efidrm
and vesadrm drivers to the kernel, it becomes much more useful. As with
the initial screen setup, these drivers can make use of the provided
EDID information for basic display output.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Neal Gompa <ngompa13@gmail.com>
Reviewed-by: Michael Chang <mchang@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/video/video.c

@@ -89,6 +89,27 @@ grub_video_get_info_and_fini (struct grub_video_mode_info *mode_info,
   return GRUB_ERR_NONE;
 }
 
+/* Get information about connected display. */
+grub_err_t
+grub_video_get_edid (struct grub_video_edid_info *edid_info)
+{
+  grub_err_t err;
+
+  if (grub_video_adapter_active == NULL)
+    return grub_error (GRUB_ERR_BAD_DEVICE, "no video mode activated");
+
+  if (grub_video_adapter_active->get_edid != NULL)
+    {
+      err = grub_video_adapter_active->get_edid (edid_info);
+      if (err != GRUB_ERR_NONE)
+	return err;
+    }
+  else
+    grub_memset (edid_info, 0, sizeof (*edid_info));
+
+  return GRUB_ERR_NONE;
+}
+
 /* Determine optimized blitting formation for specified video mode info.  */
 enum grub_video_blit_format
 grub_video_get_blit_format (struct grub_video_mode_info *mode_info)