hw/display/i2c-ddc.c

   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/log.h"
  21 #include "qemu/module.h"
  22 #include "hw/i2c/i2c.h"
  23 #include "hw/qdev-properties.h"
  24 #include "migration/vmstate.h"
  25 #include "hw/display/i2c-ddc.h"
  26
  27 #ifndef DEBUG_I2CDDC
  28 #define DEBUG_I2CDDC 0
  29 #endif
  30
  31 #define DPRINTF(fmt, ...) do {                                                 \
  32     if (DEBUG_I2CDDC) {                                                        \
  33         qemu_log("i2c-ddc: " fmt , ## __VA_ARGS__);                            \
  34     }                                                                          \
  35 } while (0)
  36
  37 static void i2c_ddc_reset(DeviceState *ds)
  38 {
  39     I2CDDCState *s = I2CDDC(ds);
  40
  41     s->firstbyte = false;
  42     s->reg = 0;
  43 }
  44
  45 static int i2c_ddc_event(I2CSlave *i2c, enum i2c_event event)
  46 {
  47     I2CDDCState *s = I2CDDC(i2c);
  48
  49     if (event == I2C_START_SEND) {
  50         s->firstbyte = true;
  51     }
  52
  53     return 0;
  54 }
  55
  56 static uint8_t i2c_ddc_rx(I2CSlave *i2c)
  57 {
  58     I2CDDCState *s = I2CDDC(i2c);
  59
  60     int value;
  61     value = s->edid_blob[s->reg % sizeof(s->edid_blob)];
  62     s->reg++;
  63     return value;
  64 }
  65
  66 static int i2c_ddc_tx(I2CSlave *i2c, uint8_t data)
  67 {
  68     I2CDDCState *s = I2CDDC(i2c);
  69     if (s->firstbyte) {
  70         s->reg = data;
  71         s->firstbyte = false;
  72         DPRINTF("[EDID] Written new pointer: %u\n", data);
  73         return 0;
  74     }
  75
  76     /* Ignore all writes */
  77     s->reg++;
  78     return 0;
  79 }
  80
  81 static void i2c_ddc_init(Object *obj)
  82 {
  83     I2CDDCState *s = I2CDDC(obj);
  84
  85     qemu_edid_generate(s->edid_blob, sizeof(s->edid_blob), &s->edid_info);
  86 }
  87
  88 static const VMStateDescription vmstate_i2c_ddc = {
  89     .name = TYPE_I2CDDC,
  90     .version_id = 1,
  91     .fields = (VMStateField[]) {
  92         VMSTATE_BOOL(firstbyte, I2CDDCState),
  93         VMSTATE_UINT8(reg, I2CDDCState),
  94         VMSTATE_END_OF_LIST()
  95     }
  96 };
  97
  98 static Property i2c_ddc_properties[] = {
  99     DEFINE_EDID_PROPERTIES(I2CDDCState, edid_info),
 100     DEFINE_PROP_END_OF_LIST(),
 101 };
 102
 103 static void i2c_ddc_class_init(ObjectClass *oc, void *data)
 104 {
 105     DeviceClass *dc = DEVICE_CLASS(oc);
 106     I2CSlaveClass *isc = I2C_SLAVE_CLASS(oc);
 107
 108     dc->reset = i2c_ddc_reset;
 109     dc->vmsd = &vmstate_i2c_ddc;
 110     device_class_set_props(dc, i2c_ddc_properties);
 111     isc->event = i2c_ddc_event;
 112     isc->recv = i2c_ddc_rx;
 113     isc->send = i2c_ddc_tx;
 114 }
 115
 116 static const TypeInfo i2c_ddc_info = {
 117     .name = TYPE_I2CDDC,
 118     .parent = TYPE_I2C_SLAVE,
 119     .instance_size = sizeof(I2CDDCState),
 120     .instance_init = i2c_ddc_init,
 121     .class_init = i2c_ddc_class_init
 122 };
 123
 124 static void ddc_register_devices(void)
 125 {
 126     type_register_static(&i2c_ddc_info);
 127 }
 128
 129 type_init(ddc_register_devices);