qemu/hw/i2c/i2c-ddc.c
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   1/* A simple I2C slave for returning monitor EDID data via DDC.
   2 *
   3 * Copyright (c) 2011 Linaro Limited
   4 * Written by Peter Maydell
   5 *
   6 *  This program is free software; you can redistribute it and/or modify
   7 *  it under the terms of the GNU General Public License version 2 as
   8 *  published by the Free Software Foundation.
   9 *
  10 *  This program is distributed in the hope that it will be useful,
  11 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 *  GNU General Public License for more details.
  14 *
  15 *  You should have received a copy of the GNU General Public License along
  16 *  with this program; if not, see <http://www.gnu.org/licenses/>.
  17 */
  18
  19#include "qemu/osdep.h"
  20#include "qemu-common.h"
  21#include "qemu/log.h"
  22#include "hw/i2c/i2c.h"
  23#include "hw/i2c/i2c-ddc.h"
  24
  25#ifndef DEBUG_I2CDDC
  26#define DEBUG_I2CDDC 0
  27#endif
  28
  29#define DPRINTF(fmt, ...) do {                                                 \
  30    if (DEBUG_I2CDDC) {                                                        \
  31        qemu_log("i2c-ddc: " fmt , ## __VA_ARGS__);                            \
  32    }                                                                          \
  33} while (0);
  34
  35/* Structure defining a monitor's characteristics in a
  36 * readable format: this should be passed to build_edid_blob()
  37 * to convert it into the 128 byte binary EDID blob.
  38 * Not all bits of the EDID are customisable here.
  39 */
  40struct EDIDData {
  41    char manuf_id[3]; /* three upper case letters */
  42    uint16_t product_id;
  43    uint32_t serial_no;
  44    uint8_t manuf_week;
  45    int manuf_year;
  46    uint8_t h_cm;
  47    uint8_t v_cm;
  48    uint8_t gamma;
  49    char monitor_name[14];
  50    char serial_no_string[14];
  51    /* Range limits */
  52    uint8_t vmin; /* Hz */
  53    uint8_t vmax; /* Hz */
  54    uint8_t hmin; /* kHz */
  55    uint8_t hmax; /* kHz */
  56    uint8_t pixclock; /* MHz / 10 */
  57    uint8_t timing_data[18];
  58};
  59
  60typedef struct EDIDData EDIDData;
  61
  62/* EDID data for a simple LCD monitor */
  63static const EDIDData lcd_edid = {
  64    /* The manuf_id ought really to be an assigned EISA ID */
  65    .manuf_id = "QMU",
  66    .product_id = 0,
  67    .serial_no = 1,
  68    .manuf_week = 1,
  69    .manuf_year = 2011,
  70    .h_cm = 40,
  71    .v_cm = 30,
  72    .gamma = 0x78,
  73    .monitor_name = "QEMU monitor",
  74    .serial_no_string = "1",
  75    .vmin = 40,
  76    .vmax = 120,
  77    .hmin = 30,
  78    .hmax = 100,
  79    .pixclock = 18,
  80    .timing_data = {
  81        /* Borrowed from a 21" LCD */
  82        0x48, 0x3f, 0x40, 0x30, 0x62, 0xb0, 0x32, 0x40, 0x40,
  83        0xc0, 0x13, 0x00, 0x98, 0x32, 0x11, 0x00, 0x00, 0x1e
  84    }
  85};
  86
  87static uint8_t manuf_char_to_int(char c)
  88{
  89    return (c - 'A') & 0x1f;
  90}
  91
  92static void write_ascii_descriptor_block(uint8_t *descblob, uint8_t blocktype,
  93                                         const char *string)
  94{
  95    /* Write an EDID Descriptor Block of the "ascii string" type */
  96    int i;
  97    descblob[0] = descblob[1] = descblob[2] = descblob[4] = 0;
  98    descblob[3] = blocktype;
  99    /* The rest is 13 bytes of ASCII; if less then the rest must
 100     * be filled with newline then spaces
 101     */
 102    for (i = 5; i < 19; i++) {
 103        descblob[i] = string[i - 5];
 104        if (!descblob[i]) {
 105            break;
 106        }
 107    }
 108    if (i < 19) {
 109        descblob[i++] = '\n';
 110    }
 111    for ( ; i < 19; i++) {
 112        descblob[i] = ' ';
 113    }
 114}
 115
 116static void write_range_limits_descriptor(const EDIDData *edid,
 117                                          uint8_t *descblob)
 118{
 119    int i;
 120    descblob[0] = descblob[1] = descblob[2] = descblob[4] = 0;
 121    descblob[3] = 0xfd;
 122    descblob[5] = edid->vmin;
 123    descblob[6] = edid->vmax;
 124    descblob[7] = edid->hmin;
 125    descblob[8] = edid->hmax;
 126    descblob[9] = edid->pixclock;
 127    descblob[10] = 0;
 128    descblob[11] = 0xa;
 129    for (i = 12; i < 19; i++) {
 130        descblob[i] = 0x20;
 131    }
 132}
 133
 134static void build_edid_blob(const EDIDData *edid, uint8_t *blob)
 135{
 136    /* Write an EDID 1.3 format blob (128 bytes) based
 137     * on the EDIDData structure.
 138     */
 139    int i;
 140    uint8_t cksum;
 141
 142    /* 00-07 : header */
 143    blob[0] = blob[7] = 0;
 144    for (i = 1 ; i < 7; i++) {
 145        blob[i] = 0xff;
 146    }
 147    /* 08-09 : manufacturer ID */
 148    blob[8] = (manuf_char_to_int(edid->manuf_id[0]) << 2)
 149        | (manuf_char_to_int(edid->manuf_id[1]) >> 3);
 150    blob[9] = (manuf_char_to_int(edid->manuf_id[1]) << 5)
 151        | manuf_char_to_int(edid->manuf_id[2]);
 152    /* 10-11 : product ID code */
 153    blob[10] = edid->product_id;
 154    blob[11] = edid->product_id >> 8;
 155    blob[12] = edid->serial_no;
 156    blob[13] = edid->serial_no >> 8;
 157    blob[14] = edid->serial_no >> 16;
 158    blob[15] = edid->serial_no >> 24;
 159    /* 16 : week of manufacture */
 160    blob[16] = edid->manuf_week;
 161    /* 17 : year of manufacture - 1990 */
 162    blob[17] = edid->manuf_year - 1990;
 163    /* 18, 19 : EDID version and revision */
 164    blob[18] = 1;
 165    blob[19] = 3;
 166    /* 20 - 24 : basic display parameters */
 167    /* We are always a digital display */
 168    blob[20] = 0x80;
 169    /* 21, 22 : max h/v size in cm */
 170    blob[21] = edid->h_cm;
 171    blob[22] = edid->v_cm;
 172    /* 23 : gamma (divide by 100 then add 1 for actual value) */
 173    blob[23] = edid->gamma;
 174    /* 24 feature support: no power management, RGB, preferred timing mode,
 175     * standard colour space
 176     */
 177    blob[24] = 0x0e;
 178    /* 25 - 34 : chromaticity coordinates. These are the
 179     * standard sRGB chromaticity values
 180     */
 181    blob[25] = 0xee;
 182    blob[26] = 0x91;
 183    blob[27] = 0xa3;
 184    blob[28] = 0x54;
 185    blob[29] = 0x4c;
 186    blob[30] = 0x99;
 187    blob[31] = 0x26;
 188    blob[32] = 0x0f;
 189    blob[33] = 0x50;
 190    blob[34] = 0x54;
 191    /* 35, 36 : Established timings: claim to support everything */
 192    blob[35] = blob[36] = 0xff;
 193    /* 37 : manufacturer's reserved timing: none */
 194    blob[37] = 0;
 195    /* 38 - 53 : standard timing identification
 196     * don't claim anything beyond what the 'established timings'
 197     * already provide. Unused slots must be (0x1, 0x1)
 198     */
 199    for (i = 38; i < 54; i++) {
 200        blob[i] = 0x1;
 201    }
 202    /* 54 - 71 : descriptor block 1 : must be preferred timing data */
 203    memcpy(blob + 54, edid->timing_data, 18);
 204    /* 72 - 89, 90 - 107, 108 - 125 : descriptor block 2, 3, 4
 205     * Order not important, but we must have a monitor name and a
 206     * range limits descriptor.
 207     */
 208    write_range_limits_descriptor(edid, blob + 72);
 209    write_ascii_descriptor_block(blob + 90, 0xfc, edid->monitor_name);
 210    write_ascii_descriptor_block(blob + 108, 0xff, edid->serial_no_string);
 211
 212    /* 126 : extension flag */
 213    blob[126] = 0;
 214
 215    cksum = 0;
 216    for (i = 0; i < 127; i++) {
 217        cksum += blob[i];
 218    }
 219    /* 127 : checksum */
 220    blob[127] = -cksum;
 221    if (DEBUG_I2CDDC) {
 222        qemu_hexdump((char *)blob, stdout, "", 128);
 223    }
 224}
 225
 226static void i2c_ddc_reset(DeviceState *ds)
 227{
 228    I2CDDCState *s = I2CDDC(ds);
 229
 230    s->firstbyte = false;
 231    s->reg = 0;
 232}
 233
 234static int i2c_ddc_event(I2CSlave *i2c, enum i2c_event event)
 235{
 236    I2CDDCState *s = I2CDDC(i2c);
 237
 238    if (event == I2C_START_SEND) {
 239        s->firstbyte = true;
 240    }
 241
 242    return 0;
 243}
 244
 245static int i2c_ddc_rx(I2CSlave *i2c)
 246{
 247    I2CDDCState *s = I2CDDC(i2c);
 248
 249    int value;
 250    value = s->edid_blob[s->reg];
 251    s->reg++;
 252    return value;
 253}
 254
 255static int i2c_ddc_tx(I2CSlave *i2c, uint8_t data)
 256{
 257    I2CDDCState *s = I2CDDC(i2c);
 258    if (s->firstbyte) {
 259        s->reg = data;
 260        s->firstbyte = false;
 261        DPRINTF("[EDID] Written new pointer: %u\n", data);
 262        return 1;
 263    }
 264
 265    /* Ignore all writes */
 266    s->reg++;
 267    return 1;
 268}
 269
 270static void i2c_ddc_init(Object *obj)
 271{
 272    I2CDDCState *s = I2CDDC(obj);
 273    build_edid_blob(&lcd_edid, s->edid_blob);
 274}
 275
 276static const VMStateDescription vmstate_i2c_ddc = {
 277    .name = TYPE_I2CDDC,
 278    .version_id = 1,
 279    .fields = (VMStateField[]) {
 280        VMSTATE_BOOL(firstbyte, I2CDDCState),
 281        VMSTATE_UINT8(reg, I2CDDCState),
 282        VMSTATE_END_OF_LIST()
 283    }
 284};
 285
 286static void i2c_ddc_class_init(ObjectClass *oc, void *data)
 287{
 288    DeviceClass *dc = DEVICE_CLASS(oc);
 289    I2CSlaveClass *isc = I2C_SLAVE_CLASS(oc);
 290
 291    dc->reset = i2c_ddc_reset;
 292    dc->vmsd = &vmstate_i2c_ddc;
 293    isc->event = i2c_ddc_event;
 294    isc->recv = i2c_ddc_rx;
 295    isc->send = i2c_ddc_tx;
 296}
 297
 298static TypeInfo i2c_ddc_info = {
 299    .name = TYPE_I2CDDC,
 300    .parent = TYPE_I2C_SLAVE,
 301    .instance_size = sizeof(I2CDDCState),
 302    .instance_init = i2c_ddc_init,
 303    .class_init = i2c_ddc_class_init
 304};
 305
 306static void ddc_register_devices(void)
 307{
 308    type_register_static(&i2c_ddc_info);
 309}
 310
 311type_init(ddc_register_devices);
 312