Sight in my Life

http://people.gnome.org/~ssp/randr/edid-parse.c

http://people.gnome.org/~ssp/randr/edid.h

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// 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 DisplayDescriptor
{
};

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;
    };
};

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;
    };

    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 char        *output_name,
				const MonitorInfo *info);

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edid.c

/*
 * 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>

#define TRUE 1
#define FALSE 0

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->digital.bits_per_primary = bit_depth[bits];

	bits = get_bits (edid[0x14], 0, 3);
	
	if (bits <= 5)
	    info->digital.interface = interfaces[bits];
	else
	    info->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->analog.video_signal_level = levels[bits][0];
	info->analog.sync_signal_level = levels[bits][1];
	info->analog.total_signal_level = levels[bits][2];

	info->analog.blank_to_black = get_bit (edid[0x14], 4);

	info->analog.separate_hv_sync = get_bit (edid[0x14], 3);
	info->analog.composite_sync_on_h = get_bit (edid[0x14], 2);
	info->analog.composite_sync_on_green = get_bit (edid[0x14], 1);

	info->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->digital.rgb444 = TRUE;
	if (get_bit (edid[0x18], 3))
	    info->digital.ycrcb444 = 1;
	if (get_bit (edid[0x18], 4))
	    info->digital.ycrcb422 = 1;
    }
    else
    {
	int bits = get_bits (edid[0x18], 3, 4);
	ColorType color_type[4] =
	{
	    MONOCHROME, RGB, OTHER_COLOR, UNDEFINED_COLOR
	};

	info->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;

	    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->digital.composite = !get_bit (bits, 3);

	if (detailed->digital.composite)
	{
	    detailed->digital.serrations = get_bit (bits, 2);
	    detailed->digital.negative_vsync = FALSE;
	}
	else
	{
	    detailed->digital.serrations = FALSE;
	    detailed->digital.negative_vsync = !get_bit (bits, 2);
	}

	detailed->digital.negative_hsync = !get_bit (bits, 0);
    }
    else
    {
	detailed->analog.bipolar = get_bit (bits, 3);
	detailed->analog.serrations = get_bit (bits, 2);
	detailed->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 = calloc (1, sizeof (MonitorInfo));

    decode_check_sum (edid, info);
    
    if (!decode_header (edid))
	return NULL;

    if (!decode_vendor_and_product_identification (edid, info))
	return NULL;

    if (!decode_edid_version (edid, info))
	return NULL;

    if (!decode_display_parameters (edid, info))
	return NULL;

    if (!decode_color_characteristics (edid, info))
	return NULL;

    if (!decode_established_timings (edid, info))
	return NULL;

    if (!decode_standard_timings (edid, info))
	return NULL;
    
    if (!decode_descriptors (edid, info))
	return NULL;
    
    return info;
}
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