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