path: root/src/lib/edid.c

/*
 * Copyright 2013 Google Inc.
 * Copyright 2006-2012 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: Adam Jackson <ajax@nwnk.net> */

/* this is a pretty robust parser for EDID, and we're tasked with parsing
 * an arbitrary panel. We will pass it a raw EDID block and a struct which
 * it must fill in with values. The set of values we need is pretty limited
 * at present.
 */

#include <stddef.h>
#include <console/console.h>
#include <arch/io.h>
#include <arch/byteorder.h>
#include <stdint.h>
#include <string.h>
#include <stdlib.h>
#include <edid.h>

static int claims_one_point_oh = 0;
static int claims_one_point_two = 0;
static int claims_one_point_three = 0;
static int claims_one_point_four = 0;
static int nonconformant_digital_display = 0;
static int nonconformant_extension = 0;
static int did_detailed_timing = 0;
static int has_name_descriptor = 0;
static int name_descriptor_terminated = 0;
static int has_range_descriptor = 0;
static int has_preferred_timing = 0;
static int has_valid_checksum = 0;
static int has_valid_cvt = 1;
static int has_valid_dummy_block = 1;
static int has_valid_week = 0;
static int has_valid_year = 0;
static int has_valid_detailed_blocks = 0;
static int has_valid_extension_count = 0;
static int has_valid_descriptor_ordering = 1;
static int has_valid_descriptor_pad = 1;
static int has_valid_range_descriptor = 1;
static int has_valid_max_dotclock = 1;
static int has_valid_string_termination = 1;
static int manufacturer_name_well_formed = 0;
static int seen_non_detailed_descriptor = 0;

static int warning_excessive_dotclock_correction = 0;
static int warning_zero_preferred_refresh = 0;

static int conformant = 1;

static char *manufacturer_name(struct edid *out, unsigned char *x)
{
	out->manuf_name[0] = ((x[0] & 0x7C) >> 2) + '@';
	out->manuf_name[1] = ((x[0] & 0x03) << 3) + ((x[1] & 0xE0) >> 5) + '@';
	out->manuf_name[2] = (x[1] & 0x1F) + '@';
	out->manuf_name[3] = 0;

	if (isupper(out->manuf_name[0]) &&
	    isupper(out->manuf_name[1]) &&
	    isupper(out->manuf_name[2]))
		manufacturer_name_well_formed = 1;

	return out->manuf_name;
}

static int
detailed_cvt_descriptor(struct edid *out, unsigned char *x, int first)
{
	const unsigned char empty[3] = { 0, 0, 0 };
	const char *names[] = { "50", "60", "75", "85" };
	int width = 0, height = 0;
	int valid = 1;
	int fifty = 0, sixty = 0, seventyfive = 0, eightyfive = 0, reduced = 0;

	if (!first && !memcmp(x, empty, 3))
		return valid;

	height = x[0];
	height |= (x[1] & 0xf0) << 4;
	height++;
	height *= 2;

	switch (x[1] & 0x0c) {
	case 0x00:
		width = (height * 4) / 3; break;
	case 0x04:
		width = (height * 16) / 9; break;
	case 0x08:
		width = (height * 16) / 10; break;
	case 0x0c:
		width = (height * 15) / 9; break;
	}

	if (x[1] & 0x03)
		valid = 0;
	if (x[2] & 0x80)
		valid = 0;
	if (!(x[2] & 0x1f))
		valid = 0;

	fifty	= (x[2] & 0x10);
	sixty	= (x[2] & 0x08);
	seventyfive = (x[2] & 0x04);
	eightyfive  = (x[2] & 0x02);
	reduced	= (x[2] & 0x01);

	if (!valid) {
		printk(BIOS_SPEW, "    (broken)\n");
	} else {
		printk(BIOS_SPEW, "    %dx%d @ ( %s%s%s%s%s) Hz (%s%s preferred)\n",
		       width, height,
		       fifty ? "50 " : "",
		       sixty ? "60 " : "",
		       seventyfive ? "75 " : "",
		       eightyfive ? "85 " : "",
		       reduced ? "60RB " : "",
		       names[(x[2] & 0x60) >> 5],
		       (((x[2] & 0x60) == 0x20) && reduced) ? "RB" : "");
	}

	return valid;
}

static int isalnum(char x)
{
	if (x >= 'a' && x <= 'z')
		return 1;
	if (x >= 'A' && x <= 'Z')
		return 1;
	if (x >= '0' && x <= '9')
		return 1;
	return 0;

}
/* extract a string from a detailed subblock, checking for termination */
static char *
extract_string(unsigned char *x, int *valid_termination, int len)
{
	static char ret[128];
	int i, seen_newline = 0;

	memset(ret, 0, sizeof(ret));

	for (i = 0; i < len; i++) {
		if (isalnum(x[i])) {
			ret[i] = x[i];
		} else if (!seen_newline) {
			if (x[i] == 0x0a) {
				seen_newline = 1;
			} else {
				*valid_termination = 0;
				return ret;
			}
		} else {
			if (x[i] != 0x20) {
				*valid_termination = 0;
				return ret;
			}
		}
	}

	return ret;
}

/* 1 means valid data */
static int
detailed_block(struct edid *out, unsigned char *x, int in_extension)
{
	static unsigned char name[53];
	int i;
#if 1
	printk(BIOS_SPEW, "Hex of detail: ");
	for (i = 0; i < 18; i++)
		printk(BIOS_SPEW, "%02x", x[i]);
	printk(BIOS_SPEW, "\n");
#endif

	if (x[0] == 0 && x[1] == 0) {
		/* Monitor descriptor block, not detailed timing descriptor. */
		if (x[2] != 0) {
			/* 1.3, 3.10.3 */
			printk(BIOS_SPEW, "Monitor descriptor block has byte 2 nonzero (0x%02x)\n",
			       x[2]);
			has_valid_descriptor_pad = 0;
		}
		if (x[3] != 0xfd && x[4] != 0x00) {
			/* 1.3, 3.10.3 */
			printk(BIOS_SPEW, "Monitor descriptor block has byte 4 nonzero (0x%02x)\n",
			       x[4]);
			has_valid_descriptor_pad = 0;
		}

		seen_non_detailed_descriptor = 1;
		if (x[3] <= 0xF) {
			/*
			 * in principle we can decode these, if we know what they are.
			 * 0x0f seems to be common in laptop panels.
			 * 0x0e is used by EPI: http://www.epi-standard.org/
			 */
			printk(BIOS_SPEW, "Manufacturer-specified data, tag %d\n", x[3]);
			return 0;
		}
		switch (x[3]) {
		case 0x10:
			printk(BIOS_SPEW, "Dummy block\n");
			for (i = 5; i < 18; i++)
				if (x[i] != 0x00)
					has_valid_dummy_block = 0;
			return 0;
		case 0xF7:
			/* TODO */
			printk(BIOS_SPEW, "Established timings III\n");
			return 0;
		case 0xF8:
		{
			int valid_cvt = 1; /* just this block */
			printk(BIOS_SPEW, "CVT 3-byte code descriptor:\n");
			if (x[5] != 0x01) {
				has_valid_cvt = 0;
				return 0;
			}
			for (i = 0; i < 4; i++)
				valid_cvt &= detailed_cvt_descriptor(out, x + 6 + (i * 3), (i == 0));
			has_valid_cvt &= valid_cvt;
			return 0;
		}
		case 0xF9:
			/* TODO */
			printk(BIOS_SPEW, "Color management data\n");
			return 0;
		case 0xFA:
			/* TODO */
			printk(BIOS_SPEW, "More standard timings\n");
			return 0;
		case 0xFB:
			/* TODO */
			printk(BIOS_SPEW, "Color point\n");
			return 0;
		case 0xFC:
			/* XXX should check for spaces after the \n */
			/* XXX check: terminated with 0x0A, padded with 0x20 */
			has_name_descriptor = 1;
			if (strchr((char *)name, '\n')) return 0;
			/* avoid strncat
			strncat((char *)name, (char *)x + 5, 13);
			*/
			if (strchr((char *)name, '\n') || strchr((char *)x+5, '\n')) {
				name_descriptor_terminated = 1;
				/* later.
				printk(BIOS_SPEW, "Monitor name: %s\n",
				       extract_string(name, &has_valid_string_termination,
						      strlen((char *)name)));
				*/
			}
			return 0;
		case 0xFD:
		{
			int h_max_offset = 0, h_min_offset = 0;
			int v_max_offset = 0, v_min_offset = 0;
			int is_cvt = 0;
			has_range_descriptor = 1;
			out->range_class = "";
			/*
			 * XXX todo: implement feature flags, vtd blocks
			 * XXX check: ranges are well-formed; block termination if no vtd
			 */
			if (claims_one_point_four) {
				if (x[4] & 0x02) {
					v_max_offset = 255;
					if (x[4] & 0x01) {
						v_min_offset = 255;
					}
				}
				if (x[4] & 0x04) {
					h_max_offset = 255;
					if (x[4] & 0x03) {
						h_min_offset = 255;
					}
				}
			} else if (x[4]) {
				has_valid_range_descriptor = 0;
			}

			/*
			 * despite the values, this is not a bitfield.
			 */
			switch (x[10]) {
			case 0x00: /* default gtf */
				out->range_class = "GTF";
				break;
			case 0x01: /* range limits only */
				out->range_class = "bare limits";
				if (!claims_one_point_four)
					has_valid_range_descriptor = 0;
				break;
			case 0x02: /* secondary gtf curve */
				out->range_class = "GTF with icing";
				break;
			case 0x04: /* cvt */
				out->range_class = "CVT";
				is_cvt = 1;
				if (!claims_one_point_four)
					has_valid_range_descriptor = 0;
				break;
			default: /* invalid */
				has_valid_range_descriptor = 0;
				out->range_class = "invalid";
				break;
			}

			if (x[5] + v_min_offset > x[6] + v_max_offset)
				has_valid_range_descriptor = 0;
			if (x[7] + h_min_offset > x[8] + h_max_offset)
				has_valid_range_descriptor = 0;
			printk(BIOS_SPEW, "Monitor ranges (%s): %d-%dHz V, %d-%dkHz H",
			       out->range_class,
			       x[5] + v_min_offset, x[6] + v_max_offset,
			       x[7] + h_min_offset, x[8] + h_max_offset);
			if (x[9])
				printk(BIOS_SPEW, ", max dotclock %dMHz\n", x[9] * 10);
			else {
				if (claims_one_point_four)
					has_valid_max_dotclock = 0;
				printk(BIOS_SPEW, "\n");
			}

			if (is_cvt) {
				int max_h_pixels = 0;

				printk(BIOS_SPEW, "CVT version %d.%d\n", x[11] & 0xf0 >> 4, x[11] & 0x0f);

				if (x[12] & 0xfc) {
					int raw_offset = (x[12] & 0xfc) >> 2;
					printk(BIOS_SPEW, "Real max dotclock: %.2fMHz\n",
					       (x[9] * 10) - (raw_offset * 0.25));
					if (raw_offset >= 40)
						warning_excessive_dotclock_correction = 1;
				}

				max_h_pixels = x[12] & 0x03;
				max_h_pixels <<= 8;
				max_h_pixels |= x[13];
				max_h_pixels *= 8;
				if (max_h_pixels)
					printk(BIOS_SPEW, "Max active pixels per line: %d\n", max_h_pixels);

				printk(BIOS_SPEW, "Supported aspect ratios: %s %s %s %s %s\n",
				       x[14] & 0x80 ? "4:3" : "",
				       x[14] & 0x40 ? "16:9" : "",
				       x[14] & 0x20 ? "16:10" : "",
				       x[14] & 0x10 ? "5:4" : "",
				       x[14] & 0x08 ? "15:9" : "");
				if (x[14] & 0x07)
					has_valid_range_descriptor = 0;

				printk(BIOS_SPEW, "Preferred aspect ratio: ");
				switch((x[15] & 0xe0) >> 5) {
				case 0x00: printk(BIOS_SPEW, "4:3"); break;
				case 0x01: printk(BIOS_SPEW, "16:9"); break;
				case 0x02: printk(BIOS_SPEW, "16:10"); break;
				case 0x03: printk(BIOS_SPEW, "5:4"); break;
				case 0x04: printk(BIOS_SPEW, "15:9"); break;
				default: printk(BIOS_SPEW, "(broken)"); break;
				}
				printk(BIOS_SPEW, "\n");

				if (x[15] & 0x04)
					printk(BIOS_SPEW, "Supports CVT standard blanking\n");
				if (x[15] & 0x10)
					printk(BIOS_SPEW, "Supports CVT reduced blanking\n");

				if (x[15] & 0x07)
					has_valid_range_descriptor = 0;

				if (x[16] & 0xf0) {
					printk(BIOS_SPEW, "Supported display scaling:\n");
					if (x[16] & 0x80)
						printk(BIOS_SPEW, "    Horizontal shrink\n");
					if (x[16] & 0x40)
						printk(BIOS_SPEW, "    Horizontal stretch\n");
					if (x[16] & 0x20)
						printk(BIOS_SPEW, "    Vertical shrink\n");
					if (x[16] & 0x10)
						printk(BIOS_SPEW, "    Vertical stretch\n");
				}

				if (x[16] & 0x0f)
					has_valid_range_descriptor = 0;

				if (x[17])
					printk(BIOS_SPEW, "Preferred vertical refresh: %d Hz\n", x[17]);
				else
					warning_zero_preferred_refresh = 1;
			}

			/*
			 * Slightly weird to return a global, but I've never seen any
			 * EDID block wth two range descriptors, so it's harmless.
			 */
			return 0;
		}
		case 0xFE:
			/*
			 * TODO: Two of these in a row, in the third and fourth slots,
			 * seems to be specified by SPWG: http://www.spwg.org/
			 */
			printk(BIOS_SPEW, "ASCII string: %s\n",
			       extract_string(x + 5, &has_valid_string_termination, 13));
			return 0;
		case 0xFF:
			printk(BIOS_SPEW, "Serial number: %s\n",
			       extract_string(x + 5, &has_valid_string_termination, 13));
			return 0;
		default:
			printk(BIOS_SPEW, "Unknown monitor description type %d\n", x[3]);
			return 0;
		}
	}

	if (seen_non_detailed_descriptor && !in_extension) {
		has_valid_descriptor_ordering = 0;
	}

	if (! did_detailed_timing){
		out->ha = (x[2] + ((x[4] & 0xF0) << 4));
		out->hbl = (x[3] + ((x[4] & 0x0F) << 8));
		out->hso = (x[8] + ((x[11] & 0xC0) << 2));
		out->hspw = (x[9] + ((x[11] & 0x30) << 4));
		out->hborder = x[15];
		out->va = (x[5] + ((x[7] & 0xF0) << 4));
		out->vbl = (x[6] + ((x[7] & 0x0F) << 8));
		out->vso = ((x[10] >> 4) + ((x[11] & 0x0C) << 2));
		out->vspw = ((x[10] & 0x0F) + ((x[11] & 0x03) << 4));
		out->vborder = x[16];
		printk(BIOS_SPEW, "Did detailed timing\n");
	}
	did_detailed_timing = 1;
	switch ((x[17] & 0x18) >> 3) {
	case 0x00:
		out->syncmethod = " analog composite";
		break;
	case 0x01:
		out->syncmethod = " bipolar analog composite";
		break;
	case 0x02:
		out->syncmethod = " digital composite";
		break;
	case 0x03:
		out->syncmethod = "";
		break;
	}
	out->pvsync = (x[17] & (1 << 2)) ? '+' : '-';
	out->phsync = (x[17] & (1 << 1)) ? '+' : '-';
	switch (x[17] & 0x61) {
	case 0x20:
		out->stereo = "field sequential L/R";
		break;
	case 0x40:
		out->stereo = "field sequential R/L";
		break;
	case 0x21:
		out->stereo = "interleaved right even";
		break;
	case 0x41:
		out->stereo = "interleaved left even";
		break;
	case 0x60:
		out->stereo = "four way interleaved";
		break;
	case 0x61:
		out->stereo = "side by side interleaved";
		break;
	default:
		out->stereo = "";
		break;
	}

	printk(BIOS_SPEW, "Detailed mode (IN HEX): Clock %d0 KHz, %x mm x %x mm\n"
	       "               %04x %04x %04x %04x hborder %x\n"
	       "               %04x %04x %04x %04x vborder %x\n"
	       "               %chsync %cvsync%s%s %s\n",
	       (x[0] + (x[1] << 8)),
	       (x[12] + ((x[14] & 0xF0) << 4)),
	       (x[13] + ((x[14] & 0x0F) << 8)),
	       out->ha, out->ha + out->hso, out->ha + out->hso + out->hspw,
	       out->ha + out->hbl, out->hborder,
	       out->va, out->va + out->vso, out->va + out->vso + out->vspw,
	       out->va + out->vbl, out->vborder,
	       out->phsync, out->pvsync,
	       out->syncmethod, x[17] & 0x80 ?" interlaced" : "",
	       out->stereo
		);
	return 1;
}

static int
do_checksum(unsigned char *x)
{
	printk(BIOS_SPEW, "Checksum: 0x%hx", x[0x7f]);
	{
		unsigned char sum = 0;
		int i;
		for (i = 0; i < 128; i++)
			sum += x[i];
		if (sum) {
			printk(BIOS_SPEW, " (should be 0x%hx)", (unsigned char)(x[0x7f] - sum));
			has_valid_checksum = 0;
		} else {
			has_valid_checksum = 1;
			printk(BIOS_SPEW, " (valid)");
		}
	}
	printk(BIOS_SPEW, "\n");
	return has_valid_checksum;
}

/* CEA extension */

static const char *
audio_format(unsigned char x)
{
	switch (x) {
	case 0: return "RESERVED";
	case 1: return "Linear PCM";
	case 2: return "AC-3";
	case 3: return "MPEG 1 (Layers 1 & 2)";
	case 4: return "MPEG 1 Layer 3 (MP3)";
	case 5: return "MPEG2 (multichannel)";
	case 6: return "AAC";
	case 7: return "DTS";
	case 8: return "ATRAC";
	case 9: return "One Bit Audio";
	case 10: return "Dolby Digital+";
	case 11: return "DTS-HD";
	case 12: return "MAT (MLP)";
	case 13: return "DST";
	case 14: return "WMA Pro";
	case 15: return "RESERVED";
	}
	return "BROKEN"; /* can't happen */
}

static void
cea_audio_block(unsigned char *x)
{
	int i, format;
	int length = x[0] & 0x1f;

	if (length % 3) {
		printk(BIOS_SPEW, "Broken CEA audio block length %d\n", length);
		/* XXX non-conformant */
		return;
	}

	for (i = 1; i < length; i += 3) {
		format = (x[i] & 0x78) >> 3;
		printk(BIOS_SPEW, "    %s, max channels %d\n", audio_format(format),
		       x[i] & 0x07);
		printk(BIOS_SPEW, "    Supported sample rates (kHz):%s%s%s%s%s%s%s\n",
		       (x[i+1] & 0x40) ? " 192" : "",
		       (x[i+1] & 0x20) ? " 176.4" : "",
		       (x[i+1] & 0x10) ? " 96" : "",
		       (x[i+1] & 0x08) ? " 88.2" : "",
		       (x[i+1] & 0x04) ? " 48" : "",
		       (x[i+1] & 0x02) ? " 44.1" : "",
		       (x[i+1] & 0x01) ? " 32" : "");
		if (format == 1) {
			printk(BIOS_SPEW, "    Supported sample sizes (bits):%s%s%s\n",
			       (x[2] & 0x04) ? " 24" : "",
			       (x[2] & 0x02) ? " 20" : "",
			       (x[2] & 0x01) ? " 16" : "");
		} else if (format <= 8) {
			printk(BIOS_SPEW, "    Maximum bit rate: %d kHz\n", x[2] * 8);
		}
	}
}

static void
cea_video_block(unsigned char *x)
{
	int i;
	int length = x[0] & 0x1f;

	for (i = 1; i < length; i++)
		printk(BIOS_SPEW,"    VIC %02d %s\n", x[i] & 0x7f,
		       x[i] & 0x80 ? "(native)" : "");
}

static void
cea_hdmi_block(struct edid *out, unsigned char *x)
{
	int length = x[0] & 0x1f;

	printk(BIOS_SPEW, " (HDMI)\n");
	printk(BIOS_SPEW,
	       "    Source physical address %d.%d.%d.%d\n",
	       x[4] >> 4, x[4] & 0x0f, x[5] >> 4, x[5] & 0x0f);

	if (length > 5) {
		if (x[6] & 0x80)
			printk(BIOS_SPEW, "    Supports_AI\n");
		if (x[6] & 0x40)
			printk(BIOS_SPEW, "    DC_48bit\n");
		if (x[6] & 0x20)
			printk(BIOS_SPEW, "    DC_36bit\n");
		if (x[6] & 0x10)
			printk(BIOS_SPEW, "    DC_30bit\n");
		if (x[6] & 0x08)
			printk(BIOS_SPEW, "    DC_Y444\n");
		/* two reserved */
		if (x[6] & 0x01)
			printk(BIOS_SPEW, "    DVI_Dual\n");
	}

	if (length > 6)
		printk(BIOS_SPEW, "    Maximum TMDS clock: %dMHz\n", x[7] * 5);

	/* XXX the walk here is really ugly, and needs to be length-checked */
	if (length > 7) {
		int b = 0;

		if (x[8] & 0x80) {
			printk(BIOS_SPEW, "    Video latency: %d\n", x[9 + b]);
			printk(BIOS_SPEW, "    Audio latency: %d\n", x[10 + b]);
			b += 2;
		}

		if (x[8] & 0x40) {
			printk(BIOS_SPEW, "    Interlaced video latency: %d\n", x[9 + b]);
			printk(BIOS_SPEW, "    Interlaced audio latency: %d\n", x[10 + b]);
			b += 2;
		}

		if (x[8] & 0x20) {
			int mask = 0, formats = 0;
			int len_xx, len_3d;
			printk(BIOS_SPEW, "    Extended HDMI video details:\n");
			if (x[9 + b] & 0x80)
				printk(BIOS_SPEW, "      3D present\n");
			if ((x[9 + b] & 0x60) == 0x20) {
				printk(BIOS_SPEW, "      All advertised VICs are 3D-capable\n");
				formats = 1;
			}
			if ((x[9 + b] & 0x60) == 0x40) {
				printk(BIOS_SPEW, "      3D-capable-VIC mask present\n");
				formats = 1;
				mask = 1;
			}
			switch (x[9 + b] & 0x18) {
			case 0x00: break;
			case 0x08:
				printk(BIOS_SPEW, "      Base EDID image size is aspect ratio\n");
				break;
			case 0x10:
				printk(BIOS_SPEW, "      Base EDID image size is in units of 1cm\n");
				break;
			case 0x18:
				printk(BIOS_SPEW, "      Base EDID image size is in units of 5cm\n");
				break;
			}
			len_xx = (x[10 + b] & 0xe0) >> 5;
			len_3d = (x[10 + b] & 0x1f) >> 0;
			b += 2;

			if (len_xx) {
				printk(BIOS_SPEW, "      Skipping %d bytes that HDMI refuses to publicly"
				       " document\n", len_xx);
				b += len_xx;
			}

			if (len_3d) {
				if (formats) {
					if (x[9 + b] & 0x01)
						printk(BIOS_SPEW, "      Side-by-side 3D supported\n");
					if (x[10 + b] & 0x40)
						printk(BIOS_SPEW, "      Top-and-bottom 3D supported\n");
					if (x[10 + b] & 0x01)
						printk(BIOS_SPEW, "      Frame-packing 3D supported\n");
					b += 2;
				}
				if (mask) {
					int i;
					printk(BIOS_SPEW, "      3D VIC indices:");
					/* worst bit ordering ever */
					for (i = 0; i < 8; i++)
						if (x[10 + b] & (1 << i))
							printk(BIOS_SPEW, " %d", i);
					for (i = 0; i < 8; i++)
						if (x[9 + b] & (1 << i))
							printk(BIOS_SPEW, " %d", i + 8);
					printk(BIOS_SPEW, "\n");
					b += 2;
				}

				/*
				 * XXX list of nibbles:
				 * 2D_VIC_Order_X
				 * 3D_Structure_X
				 * (optionally: 3D_Detail_X and reserved)
				 */
			}

		}
	}
}

static void
cea_block(struct edid *out, unsigned char *x)
{
	unsigned int oui;

	switch ((x[0] & 0xe0) >> 5) {
	case 0x01:
		printk(BIOS_SPEW, "  Audio data block\n");
		cea_audio_block(x);
		break;
	case 0x02:
		printk(BIOS_SPEW, "  Video data block\n");
		cea_video_block(x);
		break;
	case 0x03:
		/* yes really, endianness lols */
		oui = (x[3] << 16) + (x[2] << 8) + x[1];
		printk(BIOS_SPEW, "  Vendor-specific data block, OUI %06x", oui);
		if (oui == 0x000c03)
			cea_hdmi_block(out, x);
		else
			printk(BIOS_SPEW, "\n");
		break;
	case 0x04:
		printk(BIOS_SPEW, "  Speaker allocation data block\n");
		break;
	case 0x05:
		printk(BIOS_SPEW, "  VESA DTC data block\n");
		break;
	case 0x07:
		printk(BIOS_SPEW, "  Extended tag: ");
		switch (x[1]) {
		case 0x00:
			printk(BIOS_SPEW, "video capability data block\n");
			break;
		case 0x01:
			printk(BIOS_SPEW, "vendor-specific video data block\n");
			break;
		case 0x02:
			printk(BIOS_SPEW, "VESA video display device information data block\n");
			break;
		case 0x03:
			printk(BIOS_SPEW, "VESA video data block\n");
			break;
		case 0x04:
			printk(BIOS_SPEW, "HDMI video data block\n");
			break;
		case 0x05:
			printk(BIOS_SPEW, "Colorimetry data block\n");
			break;
		case 0x10:
			printk(BIOS_SPEW, "CEA miscellaneous audio fields\n");
			break;
		case 0x11:
			printk(BIOS_SPEW, "Vendor-specific audio data block\n");
			break;
		case 0x12:
			printk(BIOS_SPEW, "HDMI audio data block\n");
			break;
		default:
			if (x[1] >= 6 && x[1] <= 15)
				printk(BIOS_SPEW, "Reserved video block (%02x)\n", x[1]);
			else if (x[1] >= 19 && x[1] <= 31)
				printk(BIOS_SPEW, "Reserved audio block (%02x)\n", x[1]);
			else
				printk(BIOS_SPEW, "Unknown (%02x)\n", x[1]);
			break;
		}
		break;
	default:
	{
		int tag = (*x & 0xe0) >> 5;
		int length = *x & 0x1f;
		printk(BIOS_SPEW,
		       "  Unknown tag %d, length %d (raw %02x)\n", tag, length, *x);
		break;
	}
	}
}

static int
parse_cea(struct edid *out, unsigned char *x)
{
	int ret = 0;
	int version = x[1];
	int offset = x[2];
	unsigned char *detailed;

	if (version >= 1) do {
			if (version == 1 && x[3] != 0)
				ret = 1;

			if (offset < 4)
				break;

			if (version < 3) {
				printk(BIOS_SPEW, "%d 8-byte timing descriptors\n", (offset - 4) / 8);
				if (offset - 4 > 0)
					/* do stuff */ ;
			} else if (version == 3) {
				int i;
				printk(BIOS_SPEW, "%d bytes of CEA data\n", offset - 4);
				for (i = 4; i < offset; i += (x[i] & 0x1f) + 1) {
					cea_block(out, x + i);
				}
			}

			if (version >= 2) {
				if (x[3] & 0x80)
					printk(BIOS_SPEW, "Underscans PC formats by default\n");
				if (x[3] & 0x40)
					printk(BIOS_SPEW, "Basic audio support\n");
				if (x[3] & 0x20)
					printk(BIOS_SPEW, "Supports YCbCr 4:4:4\n");
				if (x[3] & 0x10)
					printk(BIOS_SPEW, "Supports YCbCr 4:2:2\n");
				printk(BIOS_SPEW, "%d native detailed modes\n", x[3] & 0x0f);
			}

			for (detailed = x + offset; detailed + 18 < x + 127; detailed += 18)
				if (detailed[0])
					detailed_block(out, detailed, 1);
		} while (0);

	do_checksum(x);

	return ret;
}

/* generic extension code */

static void
extension_version(struct edid *out, unsigned char *x)
{
	printk(BIOS_SPEW, "Extension version: %d\n", x[1]);
}

static int
parse_extension(struct edid *out, unsigned char *x)
{
	int conformant_extension = 0;
	printk(BIOS_SPEW, "\n");

	switch(x[0]) {
	case 0x02:
		printk(BIOS_SPEW, "CEA extension block\n");
		extension_version(out, x);
		conformant_extension = parse_cea(out, x);
		break;
	case 0x10: printk(BIOS_SPEW, "VTB extension block\n"); break;
	case 0x40: printk(BIOS_SPEW, "DI extension block\n"); break;
	case 0x50: printk(BIOS_SPEW, "LS extension block\n"); break;
	case 0x60: printk(BIOS_SPEW, "DPVL extension block\n"); break;
	case 0xF0: printk(BIOS_SPEW, "Block map\n"); break;
	case 0xFF: printk(BIOS_SPEW, "Manufacturer-specific extension block\n");
	default:
		printk(BIOS_SPEW, "Unknown extension block\n");
		break;
	}

	printk(BIOS_SPEW, "\n");

	return conformant_extension;
}

static const struct {
	int x, y, refresh;
} established_timings[] = {
	/* 0x23 bit 7 - 0 */
	{720, 400, 70},
	{720, 400, 88},
	{640, 480, 60},
	{640, 480, 67},
	{640, 480, 72},
	{640, 480, 75},
	{800, 600, 56},
	{800, 600, 60},
	/* 0x24 bit 7 - 0 */
	{800, 600, 72},
	{800, 600, 75},
	{832, 624, 75},
	{1280, 768, 87},
	{1024, 768, 60},
	{1024, 768, 70},
	{1024, 768, 75},
	{1280, 1024, 75},
	/* 0x25 bit 7*/
	{1152, 870, 75},
};

static void print_subsection(const char *name, unsigned char *edid, int start,
			     int end)
{
	int i;

	printk(BIOS_SPEW, "%s:", name);
	for (i = strlen(name); i < 15; i++)
		printk(BIOS_SPEW, " ");
	for (i = start; i <= end; i++)
		printk(BIOS_SPEW, " %02x", edid[i]);
	printk(BIOS_SPEW, "\n");
}

static void dump_breakdown(unsigned char *edid)
{
	printk(BIOS_SPEW, "Extracted contents:\n");
	print_subsection("header", edid, 0, 7);
	print_subsection("serial number", edid, 8, 17);
	print_subsection("version", edid,18, 19);
	print_subsection("basic params", edid, 20, 24);
	print_subsection("chroma info", edid, 25, 34);
	print_subsection("established", edid, 35, 37);
	print_subsection("standard", edid, 38, 53);
	print_subsection("descriptor 1", edid, 54, 71);
	print_subsection("descriptor 2", edid, 72, 89);
	print_subsection("descriptor 3", edid, 90, 107);
	print_subsection("descriptor 4", edid, 108, 125);
	print_subsection("extensions", edid, 126, 126);
	print_subsection("checksum", edid, 127, 127);
	printk(BIOS_SPEW, "\n");
}

/*
 * Given a raw edid bloc, decode it into a form
 * that other parts of coreboot can use -- mainly
 * graphics bringup functions. The raw block is
 * required to be 128 bytes long, per the standard,
 * but we have no way of checking this minimum length.
 * We accept what we are given.
 */
int decode_edid(unsigned char *edid, int size, struct edid *out)
{
	int analog, i;

	dump_breakdown(edid);

	if (!edid || memcmp(edid, "\x00\xFF\xFF\xFF\xFF\xFF\xFF\x00", 8)) {
		printk(BIOS_SPEW, "No header found\n");
		return 1;
	}
	memset(out, 0, sizeof(*out));
	manufacturer_name(out, edid + 0x08);
	out->model = (unsigned short)(edid[0x0A] + (edid[0x0B] << 8));
	out->serial = (unsigned int)(edid[0x0C] + (edid[0x0D] << 8)
				     + (edid[0x0E] << 16) + (edid[0x0F] << 24));

	printk(BIOS_SPEW, "Manufacturer: %s Model %x Serial Number %u\n",
	       out->manuf_name,
	       (unsigned short)(edid[0x0A] + (edid[0x0B] << 8)),
	       (unsigned int)(edid[0x0C] + (edid[0x0D] << 8)
			      + (edid[0x0E] << 16) + (edid[0x0F] << 24)));
		/* XXX need manufacturer ID table */

		if (edid[0x10] < 55 || edid[0x10] == 0xff) {
			has_valid_week = 1;
			if (edid[0x11] > 0x0f) {
				if (edid[0x10] == 0xff) {
					has_valid_year = 1;
					printk(BIOS_SPEW, "Made week %hd of model year %hd\n", edid[0x10],
					       edid[0x11]);
					out->week = edid[0x10];
					out->year = edid[0x11];
				} else {
					/* we know it's at least 2013, when this code was written */
					if (edid[0x11] + 90 <= 2013) {
						has_valid_year = 1;
						printk(BIOS_SPEW, "Made week %hd of %hd\n",
						       edid[0x10], edid[0x11] + 1990);
						out->week = edid[0x10];
						out->year = edid[0x11] + 1990;
					}
				}
			}
		}


	printk(BIOS_SPEW, "EDID version: %hd.%hd\n", edid[0x12], edid[0x13]);
	out->version[0] = edid[0x12];
	out->version[1] = edid[0x13];

	if (edid[0x12] == 1) {
		if (edid[0x13] > 4) {
			printk(BIOS_SPEW, "Claims > 1.4, assuming 1.4 conformance\n");
			edid[0x13] = 4;
		}
		switch (edid[0x13]) {
		case 4:
			claims_one_point_four = 1;
		case 3:
			claims_one_point_three = 1;
		case 2:
			claims_one_point_two = 1;
		default:
			break;
		}
		claims_one_point_oh = 1;
	}

	/* display section */

	if (edid[0x14] & 0x80) {
		int conformance_mask;
		analog = 0;
		printk(BIOS_SPEW, "Digital display\n");
		if (claims_one_point_four) {
			conformance_mask = 0;
			if ((edid[0x14] & 0x70) == 0x00)
				printk(BIOS_SPEW, "Color depth is undefined\n");
			else if ((edid[0x14] & 0x70) == 0x70)
				nonconformant_digital_display = 1;
			else
				printk(BIOS_SPEW, "%d bits per primary color channel\n",
				       ((edid[0x14] & 0x70) >> 3) + 4);
			out->bpp = ((edid[0x14] & 0x70) >> 3) + 4;

			switch (edid[0x14] & 0x0f) {
			case 0x00: printk(BIOS_SPEW, "Digital interface is not defined\n"); break;
			case 0x01: printk(BIOS_SPEW, "DVI interface\n"); break;
			case 0x02: printk(BIOS_SPEW, "HDMI-a interface\n"); break;
			case 0x03: printk(BIOS_SPEW, "HDMI-b interface\n"); break;
			case 0x04: printk(BIOS_SPEW, "MDDI interface\n"); break;
			case 0x05: printk(BIOS_SPEW, "DisplayPort interface\n"); break;
			default:
				nonconformant_digital_display = 1;
			}
			out->type = edid[0x14] & 0x0f;
		} else 	if (claims_one_point_two) {
			conformance_mask = 0x7E;
			if (edid[0x14] & 0x01) {
				printk(BIOS_SPEW, "DFP 1.x compatible TMDS\n");
			}
		} else
			conformance_mask = 0x7F;

		if (!nonconformant_digital_display)
			nonconformant_digital_display = edid[0x14] & conformance_mask;
		out->nonconformant = nonconformant_digital_display;
	} else {
		analog = 1;
		int voltage = (edid[0x14] & 0x60) >> 5;
		int sync = (edid[0x14] & 0x0F);
		out->voltage = voltage;
		out->sync = sync;

		printk(BIOS_SPEW, "Analog display, Input voltage level: %s V\n",
		       voltage == 3 ? "0.7/0.7" :
		       voltage == 2 ? "1.0/0.4" :
		       voltage == 1 ? "0.714/0.286" :
		       "0.7/0.3");

		if (claims_one_point_four) {
			if (edid[0x14] & 0x10)
				printk(BIOS_SPEW, "Blank-to-black setup/pedestal\n");
			else
				printk(BIOS_SPEW, "Blank level equals black level\n");
		} else if (edid[0x14] & 0x10) {
			/*
			 * XXX this is just the X text.  1.3 says "if set, display expects
			 * a blank-to-black setup or pedestal per appropriate Signal
			 * Level Standard".  Whatever _that_ means.
			 */
			printk(BIOS_SPEW, "Configurable signal levels\n");
		}

		printk(BIOS_SPEW, "Sync: %s%s%s%s\n", sync & 0x08 ? "Separate " : "",
		       sync & 0x04 ? "Composite " : "",
		       sync & 0x02 ? "SyncOnGreen " : "",
		       sync & 0x01 ? "Serration " : "");
	}


		if (edid[0x15] && edid[0x16]) {
			printk(BIOS_SPEW, "Maximum image size: %d cm x %d cm\n",
			       edid[0x15], edid[0x16]);
			out->xsize_cm = edid[0x15];
			out->ysize_cm = edid[0x16];
		} else if (claims_one_point_four && (edid[0x15] || edid[0x16])) {
			if (edid[0x15]) {
				printk(BIOS_SPEW, "Aspect ratio is %f (landscape)\n",
				       100.0/(edid[0x16] + 99));
				/* truncated to integer %. We try to avoid floating point */
				out->aspect_landscape = 10000 /(edid[0x16] + 99);
			} else {
				printk(BIOS_SPEW, "Aspect ratio is %f (portrait)\n",
				       100.0/(edid[0x15] + 99));
				out->aspect_portrait = 10000 /(edid[0x16] + 99);
			}
		} else {
			/* Either or both can be zero for 1.3 and before */
			printk(BIOS_SPEW, "Image size is variable\n");
		}

		if (edid[0x17] == 0xff) {
			if (claims_one_point_four)
				printk(BIOS_SPEW, "Gamma is defined in an extension block\n");
			else
				/* XXX Technically 1.3 doesn't say this... */
				printk(BIOS_SPEW, "Gamma: 1.0\n");
		} else printk(BIOS_SPEW, "Gamma: %d%%\n", ((edid[0x17] + 100)));
		printk(BIOS_SPEW, "Check DPMS levels\n");
		if (edid[0x18] & 0xE0) {
			printk(BIOS_SPEW, "DPMS levels:");
			if (edid[0x18] & 0x80) printk(BIOS_SPEW, " Standby");
			if (edid[0x18] & 0x40) printk(BIOS_SPEW, " Suspend");
			if (edid[0x18] & 0x20) printk(BIOS_SPEW, " Off");
			printk(BIOS_SPEW, "\n");
		}

/* FIXME: this is from 1.4 spec, check earlier */
		if (analog) {
			switch (edid[0x18] & 0x18) {
			case 0x00: printk(BIOS_SPEW, "Monochrome or grayscale display\n"); break;
			case 0x08: printk(BIOS_SPEW, "RGB color display\n"); break;
			case 0x10: printk(BIOS_SPEW, "Non-RGB color display\n"); break;
			case 0x18: printk(BIOS_SPEW, "Undefined display color type\n");
			}
		} else {
			printk(BIOS_SPEW, "Supported color formats: RGB 4:4:4");
			if (edid[0x18] & 0x10)
				printk(BIOS_SPEW, ", YCrCb 4:4:4");
			if (edid[0x18] & 0x08)
				printk(BIOS_SPEW, ", YCrCb 4:2:2");
			printk(BIOS_SPEW, "\n");
		}

		if (edid[0x18] & 0x04)
			printk(BIOS_SPEW, "Default (sRGB) color space is primary color space\n");
		if (edid[0x18] & 0x02) {
			printk(BIOS_SPEW, "First detailed timing is preferred timing\n");
			has_preferred_timing = 1;
		}
		if (edid[0x18] & 0x01)
			printk(BIOS_SPEW, "Supports GTF timings within operating range\n");

		/* XXX color section */

		printk(BIOS_SPEW, "Established timings supported:\n");
		/* it's not yet clear we want all this stuff in the edid struct.
		 * Let's wait.
		 */
		for (i = 0; i < 17; i++) {
			if (edid[0x23 + i / 8] & (1 << (7 - i % 8))) {
				printk(BIOS_SPEW, "  %dx%d@%dHz\n", established_timings[i].x,
				       established_timings[i].y, established_timings[i].refresh);
			}
		}

		printk(BIOS_SPEW, "Standard timings supported:\n");
		for (i = 0; i < 8; i++) {
			uint8_t b1 = edid[0x26 + i * 2], b2 = edid[0x26 + i * 2 + 1];
			unsigned int x, y = 0, refresh;

			if (b1 == 0x01 && b2 == 0x01)
				continue;

			if (b1 == 0) {
				printk(BIOS_SPEW, "non-conformant standard timing (0 horiz)\n");
				continue;
			}
			x = (b1 + 31) * 8;
			switch ((b2 >> 6) & 0x3) {
			case 0x00:
				if (claims_one_point_three)
					y = x * 10 / 16;
				else
					y = x;
				break;
			case 0x01:
				y = x * 3 / 4;
				break;
			case 0x02:
				y = x * 4 / 5;
				break;
			case 0x03:
				y = x * 9 / 16;
				break;
			}
			refresh = 60 + (b2 & 0x3f);

			printk(BIOS_SPEW, "  %dx%d@%dHz\n", x, y, refresh);
		}

		/* detailed timings */
		printk(BIOS_SPEW, "Detailed timings\n");
		has_valid_detailed_blocks = detailed_block(out, edid + 0x36, 0);
		if (has_preferred_timing && !did_detailed_timing)
			has_preferred_timing = 0; /* not really accurate... */
		has_valid_detailed_blocks &= detailed_block(out, edid + 0x48, 0);
		has_valid_detailed_blocks &= detailed_block(out, edid + 0x5A, 0);
		has_valid_detailed_blocks &= detailed_block(out, edid + 0x6C, 0);

		/* check this, 1.4 verification guide says otherwise */
		if (edid[0x7e]) {
			printk(BIOS_SPEW, "Has %d extension blocks\n", edid[0x7e]);
			/* 2 is impossible because of the block map */
			if (edid[0x7e] != 2)
				has_valid_extension_count = 1;
		} else {
			has_valid_extension_count = 1;
		}

		printk(BIOS_SPEW, "Checksum\n");
		do_checksum(edid);
		for(i = 0; i < size; i += 128)
			nonconformant_extension = parse_extension(out, &edid[i]);
/*
		x = edid;
		for (edid_lines /= 8; edid_lines > 1; edid_lines--) {
			x += 128;
			nonconformant_extension += parse_extension(x);
		}
*/

		if (claims_one_point_three) {
			if (nonconformant_digital_display ||
			    !has_valid_string_termination ||
			    !has_valid_descriptor_pad ||
			    !has_name_descriptor ||
			    !name_descriptor_terminated ||
			    !has_preferred_timing ||
			    !has_range_descriptor)
				conformant = 0;
			if (!conformant)
				printk(BIOS_ERR, "EDID block does NOT conform to EDID 1.3!\n");
			if (nonconformant_digital_display)
				printk(BIOS_ERR, "\tDigital display field contains garbage: %x\n",
				       nonconformant_digital_display);
			if (!has_name_descriptor)
				printk(BIOS_ERR, "\tMissing name descriptor\n");
			else if (!name_descriptor_terminated)
				printk(BIOS_ERR, "\tName descriptor not terminated with a newline\n");
			if (!has_preferred_timing)
				printk(BIOS_ERR, "\tMissing preferred timing\n");
			if (!has_range_descriptor)
				printk(BIOS_ERR, "\tMissing monitor ranges\n");
			if (!has_valid_descriptor_pad) /* Might be more than just 1.3 */
				printk(BIOS_ERR, "\tInvalid descriptor block padding\n");
			if (!has_valid_string_termination) /* Likewise */
				printk(BIOS_ERR, "\tDetailed block string not properly terminated\n");
		} else if (claims_one_point_two) {
			if (nonconformant_digital_display ||
			    (has_name_descriptor && !name_descriptor_terminated))
				conformant = 0;
			if (!conformant)
				printk(BIOS_ERR, "EDID block does NOT conform to EDID 1.2!\n");
			if (nonconformant_digital_display)
				printk(BIOS_ERR, "\tDigital display field contains garbage: %x\n",
				       nonconformant_digital_display);
			if (has_name_descriptor && !name_descriptor_terminated)
				printk(BIOS_ERR, "\tName descriptor not terminated with a newline\n");
		} else if (claims_one_point_oh) {
			if (seen_non_detailed_descriptor)
				conformant = 0;
			if (!conformant)
				printk(BIOS_ERR, "EDID block does NOT conform to EDID 1.0!\n");
			if (seen_non_detailed_descriptor)
				printk(BIOS_ERR, "\tHas descriptor blocks other than detailed timings\n");
		}

		if (nonconformant_extension ||
		    !has_valid_checksum ||
		    !has_valid_cvt ||
		    !has_valid_year ||
		    !has_valid_week ||
		    !has_valid_detailed_blocks ||
		    !has_valid_dummy_block ||
		    !has_valid_extension_count ||
		    !has_valid_descriptor_ordering ||
		    !has_valid_range_descriptor ||
		    !manufacturer_name_well_formed) {
			conformant = 0;
			printk(BIOS_ERR, "EDID block does not conform at all!\n");
			if (nonconformant_extension)
				printk(BIOS_ERR, "\tHas %d nonconformant extension block(s)\n",
				       nonconformant_extension);
			if (!has_valid_checksum)
				printk(BIOS_ERR, "\tBlock has broken checksum\n");
			if (!has_valid_cvt)
				printk(BIOS_ERR, "\tBroken 3-byte CVT blocks\n");
			if (!has_valid_year)
				printk(BIOS_ERR, "\tBad year of manufacture\n");
			if (!has_valid_week)
				printk(BIOS_ERR, "\tBad week of manufacture\n");
			if (!has_valid_detailed_blocks)
				printk(BIOS_ERR, "\tDetailed blocks filled with garbage\n");
			if (!has_valid_dummy_block)
				printk(BIOS_ERR, "\tDummy block filled with garbage\n");
			if (!has_valid_extension_count)
				printk(BIOS_ERR, "\tImpossible extension block count\n");
			if (!manufacturer_name_well_formed)
				printk(BIOS_ERR, "\tManufacturer name field contains garbage\n");
			if (!has_valid_descriptor_ordering)
				printk(BIOS_ERR, "\tInvalid detailed timing descriptor ordering\n");
			if (!has_valid_range_descriptor)
				printk(BIOS_ERR, "\tRange descriptor contains garbage\n");
			if (!has_valid_max_dotclock)
				printk(BIOS_ERR, "\tEDID 1.4 block does not set max dotclock\n");
		}

		if (warning_excessive_dotclock_correction)
			printk(BIOS_ERR,
			       "Warning: CVT block corrects dotclock by more than 9.75MHz\n");
		if (warning_zero_preferred_refresh)
			printk(BIOS_ERR,
			       "Warning: CVT block does not set preferred refresh rate\n");
		return !conformant;
	}

/*
 * Notes on panel extensions: (TODO, implement me in the code)
 *
 * EPI: http://www.epi-standard.org/fileadmin/spec/EPI_Specification1.0.pdf
 * at offset 0x6c (fourth detailed block): (all other bits reserved)
 * 0x6c: 00 00 00 0e 00
 * 0x71: bit 6-5: data color mapping (00 conventional/fpdi/vesa, 01 openldi)
 *       bit 4-3: pixels per clock (00 1, 01 2, 10 4, 11 reserved)
 *       bit 2-0: bits per pixel (000 18, 001 24, 010 30, else reserved)
 * 0x72: bit 5: FPSCLK polarity (0 normal 1 inverted)
 *       bit 4: DE polarity (0 high active 1 low active)
 *       bit 3-0: interface (0000 LVDS TFT
 *                           0001 mono STN 4/8bit
 *                           0010 color STN 8/16 bit
 *                           0011 18 bit tft
 *                           0100 24 bit tft
 *                           0101 tmds
 *                           else reserved)
 * 0x73: bit 1: horizontal display mode (0 normal 1 right/left reverse)
 *       bit 0: vertical display mode (0 normal 1 up/down reverse)
 * 0x74: bit 7-4: total poweroff seq delay (0000 vga controller default
 *                                          else time in 10ms (10ms to 150ms))
 *       bit 3-0: total poweron seq delay (as above)
 * 0x75: contrast power on/off seq delay, same as 0x74
 * 0x76: bit 7: backlight control enable (1 means this field is valid)
 *       bit 6: backlight enabled at boot (0 on 1 off)
 *       bit 5-0: backlight brightness control steps (0..63)
 * 0x77: bit 7: contrast control, same bit pattern as 0x76 except bit 6 resvd
 * 0x78 - 0x7c: reserved
 * 0x7d: bit 7-4: EPI descriptor major version (1)
 *       bit 3-0: EPI descriptor minor version (0)
 *
 * ----
 *
 * SPWG: http://www.spwg.org/spwg_spec_version3.8_3-14-2007.pdf
 *
 * Since these are "dummy" blocks, terminate with 0a 20 20 20 ... as usual
 *
 * detailed descriptor 3:
 * 0x5a - 0x5e: 00 00 00 fe 00
 * 0x5f - 0x63: PC maker part number
 * 0x64: LCD supplier revision #
 * 0x65 - 0x6b: manufacturer part number
 *
 * detailed descriptor 4:
 * 0x6c - 0x70: 00 00 00 fe 00
 * 0x71 - 0x78: smbus nits values (whut)
 * 0x79: number of lvds channels (1 or 2)
 * 0x7A: panel self test (1 if present)
 * and then dummy terminator
 *
 * SPWG also says something strange about the LSB of detailed descriptor 1:
 * "LSB is set to "1" if panel is DE-timing only. H/V can be ignored."
 */