hw/i2c-ddc.c: Implement DDC I2C slave

Implement an I2C slave which implements DDC and returns the
EDID data for an attached monitor.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

2 files changed, 301 insertions, 0 deletions

diff --git a/hw/Makefile.objs b/hw/Makefile.objs
index eed7c324c8..0cc7e94b7d 100644
--- a/hw/Makefile.objs
+++ b/hw/Makefile.objs
@@ -137,6 +137,7 @@ common-obj-$(CONFIG_ADS7846) += ads7846.o
 common-obj-$(CONFIG_MAX111X) += max111x.o
 common-obj-$(CONFIG_DS1338) += ds1338.o
 common-obj-y += i2c.o spi.o smbus.o smbus_eeprom.o
+common-obj-y += i2c-ddc.o
 common-obj-y += eeprom93xx.o
 common-obj-y += scsi-disk.o cdrom.o
 common-obj-y += scsi-generic.o scsi-bus.o
diff --git a/hw/i2c-ddc.c b/hw/i2c-ddc.c
new file mode 100644
index 0000000000..b7d7a52a12
--- /dev/null
+++ b/hw/i2c-ddc.c
@@ -0,0 +1,300 @@
+/* A simple I2C slave for returning monitor EDID data via DDC.
+ *
+ * Copyright (c) 2011 Linaro Limited
+ * Written by Peter Maydell
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2 as
+ *  published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+#include "i2c.h"
+
+//#define DEBUG_I2CDDC
+#ifdef DEBUG_I2CDDC
+#define DPRINTF(fmt, ...) do { printf(fmt , ## __VA_ARGS__); } while (0)
+#else
+#define DPRINTF(fmt, ...) do {} while(0)
+#endif
+
+/* Structure defining a monitor's characteristics in a
+ * readable format: this should be passed to build_edid_blob()
+ * to convert it into the 128 byte binary EDID blob.
+ * Not all bits of the EDID are customisable here.
+ */
+typedef struct {
+    char manuf_id[3]; /* three upper case letters */
+    uint16_t product_id;
+    uint32_t serial_no;
+    uint8_t manuf_week;
+    int manuf_year;
+    uint8_t h_cm;
+    uint8_t v_cm;
+    uint8_t gamma;
+    char monitor_name[14];
+    char serial_no_string[14];
+    /* Range limits */
+    uint8_t vmin; /* Hz */
+    uint8_t vmax; /* Hz */
+    uint8_t hmin; /* kHz */
+    uint8_t hmax; /* kHz */
+    uint8_t pixclock; /* MHz / 10 */
+    uint8_t timing_data[18];
+} edid_data;
+
+/* EDID data for a simple LCD monitor */
+static const edid_data lcd_edid = {
+    /* The manuf_id ought really to be an assigned EISA ID */
+    .manuf_id = "QMU",
+    .product_id = 0,
+    .serial_no = 1,
+    .manuf_week = 1,
+    .manuf_year = 2011,
+    .h_cm = 40,
+    .v_cm = 30,
+    .gamma = 0x78,
+    .monitor_name = "QEMU monitor",
+    .serial_no_string = "1",
+    .vmin = 40,
+    .vmax = 120,
+    .hmin = 30,
+    .hmax = 100,
+    .pixclock = 18,
+    .timing_data = {
+        /* Borrowed from a 21" LCD */
+        0x48, 0x3f, 0x40, 0x30, 0x62, 0xb0, 0x32, 0x40, 0x40,
+        0xc0, 0x13, 0x00, 0x98, 0x32, 0x11, 0x00, 0x00, 0x1e
+    }
+};
+
+static uint8_t manuf_char_to_int(char c)
+{
+    return (c - 'A') & 0x1f;
+}
+
+static void write_ascii_descriptor_block(uint8_t *descblob, uint8_t blocktype,
+                                         const char *string)
+{
+    /* Write an EDID Descriptor Block of the "ascii string" type */
+    int i;
+    descblob[0] = descblob[1] = descblob[2] = descblob[4] = 0;
+    descblob[3] = blocktype;
+    /* The rest is 13 bytes of ASCII; if less then the rest must
+     * be filled with newline then spaces
+     */
+    for (i = 5; i < 19; i++) {
+        descblob[i] = string[i - 5];
+        if (!descblob[i]) {
+            break;
+        }
+    }
+    if (i < 19) {
+        descblob[i++] = '\n';
+    }
+    for ( ; i < 19; i++) {
+        descblob[i] = ' ';
+    }
+}
+
+static void write_range_limits_descriptor(const edid_data *edid,
+                                          uint8_t *descblob)
+{
+    int i;
+    descblob[0] = descblob[1] = descblob[2] = descblob[4] = 0;
+    descblob[3] = 0xfd;
+    descblob[5] = edid->vmin;
+    descblob[6] = edid->vmax;
+    descblob[7] = edid->hmin;
+    descblob[8] = edid->hmax;
+    descblob[9] = edid->pixclock;
+    descblob[10] = 0;
+    descblob[11] = 0xa;
+    for (i = 12; i < 19; i++) {
+        descblob[i] = 0x20;
+    }
+}
+
+static void build_edid_blob(const edid_data *edid, uint8_t *blob)
+{
+    /* Write an EDID 1.3 format blob (128 bytes) based
+     * on the edid_data structure.
+     */
+    int i;
+    uint8_t cksum;
+
+    /* 00-07 : header */
+    blob[0] = blob[7] = 0;
+    for (i = 1 ; i < 7; i++) {
+        blob[i] = 0xff;
+    }
+    /* 08-09 : manufacturer ID */
+    blob[8] = (manuf_char_to_int(edid->manuf_id[0]) << 2)
+        | (manuf_char_to_int(edid->manuf_id[1]) >> 3);
+    blob[9] = (manuf_char_to_int(edid->manuf_id[1]) << 5)
+        | manuf_char_to_int(edid->manuf_id[2]);
+    /* 10-11 : product ID code */
+    blob[10] = edid->product_id;
+    blob[11] = edid->product_id >> 8;
+    blob[12] = edid->serial_no;
+    blob[13] = edid->serial_no >> 8;
+    blob[14] = edid->serial_no >> 16;
+    blob[15] = edid->serial_no >> 24;
+    /* 16 : week of manufacture */
+    blob[16] = edid->manuf_week;
+    /* 17 : year of manufacture - 1990 */
+    blob[17] = edid->manuf_year - 1990;
+    /* 18, 19 : EDID version and revision */
+    blob[18] = 1;
+    blob[19] = 3;
+    /* 20 - 24 : basic display parameters */
+    /* We are always a digital display */
+    blob[20] = 0x80;
+    /* 21, 22 : max h/v size in cm */
+    blob[21] = edid->h_cm;
+    blob[22] = edid->v_cm;
+    /* 23 : gamma (divide by 100 then add 1 for actual value) */
+    blob[23] = edid->gamma;
+    /* 24 feature support: no power management, RGB, preferred timing mode,
+     * standard colour space
+     */
+    blob[24] = 0x0e;
+    /* 25 - 34 : chromaticity coordinates. These are the
+     * standard sRGB chromaticity values
+     */
+    blob[25] = 0xee;
+    blob[26] = 0x91;
+    blob[27] = 0xa3;
+    blob[28] = 0x54;
+    blob[29] = 0x4c;
+    blob[30] = 0x99;
+    blob[31] = 0x26;
+    blob[32] = 0x0f;
+    blob[33] = 0x50;
+    blob[34] = 0x54;
+    /* 35, 36 : Established timings: claim to support everything */
+    blob[35] = blob[36] = 0xff;
+    /* 37 : manufacturer's reserved timing: none */
+    blob[37] = 0;
+    /* 38 - 53 : standard timing identification
+     * don't claim anything beyond what the 'established timings'
+     * already provide. Unused slots must be (0x1, 0x1)
+     */
+    for (i = 38; i < 54; i++) {
+        blob[i] = 0x1;
+    }
+    /* 54 - 71 : descriptor block 1 : must be preferred timing data */
+    memcpy(blob + 54, edid->timing_data, 18);
+    /* 72 - 89, 90 - 107, 108 - 125 : descriptor block 2, 3, 4
+     * Order not important, but we must have a monitor name and a
+     * range limits descriptor.
+     */
+    write_range_limits_descriptor(edid, blob + 72);
+    write_ascii_descriptor_block(blob + 90, 0xfc, edid->monitor_name);
+    write_ascii_descriptor_block(blob + 108, 0xff, edid->serial_no_string);
+
+    /* 126 : extension flag */
+    blob[126] = 0;
+
+    cksum = 0;
+    DPRINTF("EDID blob:");
+    for (i = 0; i < 127; i++) {
+        cksum += blob[i];
+        DPRINTF("%c0x%02x,", i % 8 ? ' ' : '\n', blob[i]);
+    }
+    /* 127 : checksum */
+    blob[127] = -cksum;
+    DPRINTF(" 0x%02x\n", blob[127]);
+}
+
+
+
+/* A simple I2C slave which just returns the contents of its EDID blob. */
+
+typedef struct I2CDDCState_s {
+    I2CSlave i2c;
+    int firstbyte;
+    uint8_t reg;
+    uint8_t edid_blob[128];
+} I2CDDCState;
+
+static void i2c_ddc_reset(DeviceState *ds)
+{
+    I2CDDCState *s = FROM_I2C_SLAVE(I2CDDCState, I2C_SLAVE_FROM_QDEV(ds));
+    s->firstbyte = 0;
+    s->reg = 0;
+}
+
+static void i2c_ddc_event(I2CSlave *i2c, enum i2c_event event)
+{
+    I2CDDCState *s = FROM_I2C_SLAVE(I2CDDCState, i2c);
+    if (event == I2C_START_SEND) {
+        s->firstbyte = 1;
+    }
+}
+
+static int i2c_ddc_rx(I2CSlave *i2c)
+{
+    I2CDDCState *s = FROM_I2C_SLAVE(I2CDDCState, i2c);
+    int value;
+    if (s->reg < sizeof(s->edid_blob)) {
+        value = s->edid_blob[s->reg];
+    } else {
+        value = 0;
+    }
+    s->reg++;
+    return value;
+}
+
+static int i2c_ddc_tx(I2CSlave *i2c, uint8_t data)
+{
+    I2CDDCState *s = FROM_I2C_SLAVE(I2CDDCState, i2c);
+    if (s->firstbyte) {
+        s->reg = data;
+        s->firstbyte = 0;
+        return 1;
+    }
+
+    /* Ignore all writes */
+    s->reg++;
+    return 1;
+}
+
+static int i2c_ddc_init(I2CSlave *i2c)
+{
+    I2CDDCState *s = FROM_I2C_SLAVE(I2CDDCState, i2c);
+    build_edid_blob(&lcd_edid, s->edid_blob);
+    return 0;
+}
+
+static void i2c_ddc_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    I2CSlaveClass *k = I2C_SLAVE_CLASS(klass);
+    k->init = i2c_ddc_init;
+    k->event = i2c_ddc_event;
+    k->recv = i2c_ddc_rx;
+    k->send = i2c_ddc_tx;
+    dc->reset = i2c_ddc_reset;
+    // XXX vmstate?
+}
+
+static TypeInfo i2c_ddc_info = {
+    .name = "i2c-ddc",
+    .parent = TYPE_I2C_SLAVE,
+    .instance_size = sizeof(I2CDDCState),
+    .class_init = i2c_ddc_class_init,
+};
+
+static void ddc_register_types(void)
+{
+    type_register_static(&i2c_ddc_info);
+}
+
+type_init(ddc_register_types);