display/edid: add edid generator to qemu.

EDID is a metadata format to describe monitors.  On physical hardware
the monitor has an eeprom with that data block which can be read over
i2c bus.

On a linux system you can usually find the EDID data block in
/sys/class/drm/$card/$connector/edid.  xorg ships a edid-decode utility
which you can use to turn the blob into readable form.

I think it would be a good idea to use EDID for virtual displays too.
Needs changes in both qemu and guest kms drivers.  This patch is the
first step, it adds an generator for EDID blobs to qemu.  Comes with a
qemu-edid test tool included.

With EDID we can pass more information to the guest.  Names and serial
numbers, so the guests display configuration has no boring "Unknown
Monitor".  List of video modes.  Display resolution, pretty important
in case we want add HiDPI support some day.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id: 20180925075646.25114-2-kraxel@redhat.com

2 files changed, 427 insertions, 0 deletions

diff --git a/hw/display/Makefile.objs b/hw/display/Makefile.objs
index a606fb7404..492404c09e 100644
--- a/hw/display/Makefile.objs
+++ b/hw/display/Makefile.objs
@@ -1,3 +1,5 @@
+common-obj-y += edid-generate.o
+
 common-obj-$(CONFIG_FW_CFG_DMA) += ramfb.o
 common-obj-$(CONFIG_FW_CFG_DMA) += ramfb-standalone.o
 
diff --git a/hw/display/edid-generate.c b/hw/display/edid-generate.c
new file mode 100644
index 0000000000..b3e493da19
--- /dev/null
+++ b/hw/display/edid-generate.c
@@ -0,0 +1,425 @@
+/*
+ * QEMU EDID generator.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "qemu/bswap.h"
+#include "hw/display/edid.h"
+
+static const struct edid_mode {
+    uint32_t xres;
+    uint32_t yres;
+    uint32_t byte;
+    uint32_t xtra3;
+    uint32_t bit;
+    uint32_t dta;
+} modes[] = {
+    /* dea/dta extension timings (all @ 50 Hz) */
+    { .xres = 5120,   .yres = 2160,   .dta = 125 },
+    { .xres = 4096,   .yres = 2160,   .dta = 101 },
+    { .xres = 3840,   .yres = 2160,   .dta =  96 },
+    { .xres = 2560,   .yres = 1080,   .dta =  89 },
+    { .xres = 2048,   .yres = 1152 },
+    { .xres = 1920,   .yres = 1080,   .dta =  31 },
+
+    /* additional standard timings 3 (all @ 60Hz) */
+    { .xres = 1920,   .yres = 1440,   .xtra3 = 11,   .bit = 5 },
+    { .xres = 1920,   .yres = 1200,   .xtra3 = 10,   .bit = 0 },
+    { .xres = 1856,   .yres = 1392,   .xtra3 = 10,   .bit = 3 },
+    { .xres = 1792,   .yres = 1344,   .xtra3 = 10,   .bit = 5 },
+    { .xres = 1600,   .yres = 1200,   .xtra3 =  9,   .bit = 2 },
+    { .xres = 1680,   .yres = 1050,   .xtra3 =  9,   .bit = 5 },
+    { .xres = 1440,   .yres = 1050,   .xtra3 =  8,   .bit = 1 },
+    { .xres = 1440,   .yres =  900,   .xtra3 =  8,   .bit = 5 },
+    { .xres = 1360,   .yres =  768,   .xtra3 =  8,   .bit = 7 },
+    { .xres = 1280,   .yres = 1024,   .xtra3 =  7,   .bit = 1 },
+    { .xres = 1280,   .yres =  960,   .xtra3 =  7,   .bit = 3 },
+    { .xres = 1280,   .yres =  768,   .xtra3 =  7,   .bit = 6 },
+
+    /* established timings (all @ 60Hz) */
+    { .xres = 1024,   .yres =  768,   .byte  = 36,   .bit = 3 },
+    { .xres =  800,   .yres =  600,   .byte  = 35,   .bit = 0 },
+    { .xres =  640,   .yres =  480,   .byte  = 35,   .bit = 5 },
+};
+
+static void edid_ext_dta(uint8_t *dta)
+{
+    dta[0] = 0x02;
+    dta[1] = 0x03;
+    dta[2] = 0x05;
+    dta[3] = 0x00;
+
+    /* video data block */
+    dta[4] = 0x40;
+}
+
+static void edid_ext_dta_mode(uint8_t *dta, uint8_t nr)
+{
+    dta[dta[2]] = nr;
+    dta[2]++;
+    dta[4]++;
+}
+
+static int edid_std_mode(uint8_t *mode, uint32_t xres, uint32_t yres)
+{
+    uint32_t aspect;
+
+    if (xres == 0 || yres == 0) {
+        mode[0] = 0x01;
+        mode[1] = 0x01;
+        return 0;
+
+    } else if (xres * 10 == yres * 16) {
+        aspect = 0;
+    } else if (xres * 3 == yres * 4) {
+        aspect = 1;
+    } else if (xres * 4 == yres * 5) {
+        aspect = 2;
+    } else if (xres * 9 == yres * 16) {
+        aspect = 3;
+    } else {
+        return -1;
+    }
+
+    if ((xres / 8) - 31 > 255) {
+        return -1;
+    }
+
+    mode[0] = (xres / 8) - 31;
+    mode[1] = ((aspect << 6) | (60 - 60));
+    return 0;
+}
+
+static void edid_fill_modes(uint8_t *edid, uint8_t *xtra3, uint8_t *dta,
+                            uint32_t maxx, uint32_t maxy)
+{
+    const struct edid_mode *mode;
+    int std = 38;
+    int rc, i;
+
+    for (i = 0; i < ARRAY_SIZE(modes); i++) {
+        mode = modes + i;
+
+        if ((maxx && mode->xres > maxx) ||
+            (maxy && mode->yres > maxy)) {
+            continue;
+        }
+
+        if (mode->byte) {
+            edid[mode->byte] |= (1 << mode->bit);
+        } else if (mode->xtra3 && xtra3) {
+            xtra3[mode->xtra3] |= (1 << mode->bit);
+        } else if (std < 54) {
+            rc = edid_std_mode(edid + std, mode->xres, mode->yres);
+            if (rc == 0) {
+                std += 2;
+            }
+        }
+
+        if (dta && mode->dta) {
+            edid_ext_dta_mode(dta, mode->dta);
+        }
+    }
+
+    while (std < 54) {
+        edid_std_mode(edid + std, 0, 0);
+        std += 2;
+    }
+}
+
+static void edid_checksum(uint8_t *edid)
+{
+    uint32_t sum = 0;
+    int i;
+
+    for (i = 0; i < 127; i++) {
+        sum += edid[i];
+    }
+    sum &= 0xff;
+    if (sum) {
+        edid[127] = 0x100 - sum;
+    }
+}
+
+static void edid_desc_type(uint8_t *desc, uint8_t type)
+{
+    desc[0] = 0;
+    desc[1] = 0;
+    desc[2] = 0;
+    desc[3] = type;
+    desc[4] = 0;
+}
+
+static void edid_desc_text(uint8_t *desc, uint8_t type,
+                           const char *text)
+{
+    size_t len;
+
+    edid_desc_type(desc, type);
+    memset(desc + 5, ' ', 13);
+
+    len = strlen(text);
+    if (len > 12) {
+        len = 12;
+    }
+    strncpy((char *)(desc + 5), text, len);
+    desc[5 + len] = '\n';
+}
+
+static void edid_desc_ranges(uint8_t *desc)
+{
+    edid_desc_type(desc, 0xfd);
+
+    /* vertical (50 -> 125 Hz) */
+    desc[5] =  50;
+    desc[6] = 125;
+
+    /* horizontal (30 -> 160 kHz) */
+    desc[7] =  30;
+    desc[8] = 160;
+
+    /* max dot clock (1200 MHz) */
+    desc[9] = 1200 / 10;
+
+    /* no extended timing information */
+    desc[10] = 0x01;
+
+    /* padding */
+    desc[11] = '\n';
+    memset(desc + 12, ' ', 6);
+}
+
+/* additional standard timings 3 */
+static void edid_desc_xtra3_std(uint8_t *desc)
+{
+    edid_desc_type(desc, 0xf7);
+    desc[5] = 10;
+}
+
+static void edid_desc_dummy(uint8_t *desc)
+{
+    edid_desc_type(desc, 0x10);
+}
+
+static void edid_desc_timing(uint8_t *desc,
+                             uint32_t xres, uint32_t yres,
+                             uint32_t dpi)
+{
+    /* physical display size */
+    uint32_t xmm = xres * dpi / 254;
+    uint32_t ymm = yres * dpi / 254;
+
+    /* pull some realistic looking timings out of thin air */
+    uint32_t xfront = xres * 25 / 100;
+    uint32_t xsync  = xres *  3 / 100;
+    uint32_t xblank = xres * 35 / 100;
+
+    uint32_t yfront = yres *  5 / 1000;
+    uint32_t ysync  = yres *  5 / 1000;
+    uint32_t yblank = yres * 35 / 1000;
+
+    uint32_t clock  = 75 * (xres + xblank) * (yres + yblank);
+
+    *(uint32_t *)(desc) = cpu_to_le32(clock / 10000);
+
+    desc[2] = xres   & 0xff;
+    desc[3] = xblank & 0xff;
+    desc[4] = (((xres   & 0xf00) >> 4) |
+               ((xblank & 0xf00) >> 8));
+
+    desc[5] = yres   & 0xff;
+    desc[6] = yblank & 0xff;
+    desc[7] = (((yres   & 0xf00) >> 4) |
+               ((yblank & 0xf00) >> 8));
+
+    desc[8] = xfront & 0xff;
+    desc[9] = xsync  & 0xff;
+
+    desc[10] = (((yfront & 0x00f) << 4) |
+                ((ysync  & 0x00f) << 0));
+    desc[11] = (((xfront & 0x300) >> 2) |
+                ((xsync  & 0x300) >> 4) |
+                ((yfront & 0x030) >> 2) |
+                ((ysync  & 0x030) >> 4));
+
+    desc[12] = xmm & 0xff;
+    desc[13] = ymm & 0xff;
+    desc[14] = (((xmm & 0xf00) >> 4) |
+                ((ymm & 0xf00) >> 8));
+
+    desc[17] = 0x18;
+}
+
+static uint32_t edid_to_10bit(float value)
+{
+    return (uint32_t)(value * 1024 + 0.5);
+}
+
+static void edid_colorspace(uint8_t *edid,
+                            float rx, float ry,
+                            float gx, float gy,
+                            float bx, float by,
+                            float wx, float wy)
+{
+    uint32_t red_x   = edid_to_10bit(rx);
+    uint32_t red_y   = edid_to_10bit(ry);
+    uint32_t green_x = edid_to_10bit(gx);
+    uint32_t green_y = edid_to_10bit(gy);
+    uint32_t blue_x  = edid_to_10bit(bx);
+    uint32_t blue_y  = edid_to_10bit(by);
+    uint32_t white_x = edid_to_10bit(wx);
+    uint32_t white_y = edid_to_10bit(wy);
+
+    edid[25] = (((red_x   & 0x03) << 6) |
+                ((red_y   & 0x03) << 4) |
+                ((green_x & 0x03) << 2) |
+                ((green_y & 0x03) << 0));
+    edid[26] = (((blue_x  & 0x03) << 6) |
+                ((blue_y  & 0x03) << 4) |
+                ((white_x & 0x03) << 2) |
+                ((white_y & 0x03) << 0));
+    edid[27] = red_x   >> 2;
+    edid[28] = red_y   >> 2;
+    edid[29] = green_x >> 2;
+    edid[30] = green_y >> 2;
+    edid[31] = blue_x  >> 2;
+    edid[32] = blue_y  >> 2;
+    edid[33] = white_x >> 2;
+    edid[34] = white_y >> 2;
+}
+
+void qemu_edid_generate(uint8_t *edid, size_t size,
+                        qemu_edid_info *info)
+{
+    uint32_t desc = 54;
+    uint8_t *xtra3 = NULL;
+    uint8_t *dta = NULL;
+
+    /* =============== set defaults  =============== */
+
+    if (!info->vendor || strlen(info->vendor) != 3) {
+        info->vendor = "EMU";
+    }
+    if (!info->name) {
+        info->name = "QEMU Monitor";
+    }
+    if (!info->dpi) {
+        info->dpi = 100;
+    }
+    if (!info->prefx) {
+        info->prefx = 1024;
+    }
+    if (!info->prefy) {
+        info->prefy = 768;
+    }
+
+    /* =============== extensions  =============== */
+
+    if (size >= 256) {
+        dta = edid + 128;
+        edid[126]++;
+        edid_ext_dta(dta);
+    }
+
+    /* =============== header information =============== */
+
+    /* fixed */
+    edid[0] = 0x00;
+    edid[1] = 0xff;
+    edid[2] = 0xff;
+    edid[3] = 0xff;
+    edid[4] = 0xff;
+    edid[5] = 0xff;
+    edid[6] = 0xff;
+    edid[7] = 0x00;
+
+    /* manufacturer id, product code, serial number */
+    uint16_t vendor_id = ((((info->vendor[0] - '@') & 0x1f) << 10) |
+                          (((info->vendor[1] - '@') & 0x1f) <<  5) |
+                          (((info->vendor[2] - '@') & 0x1f) <<  0));
+    uint16_t model_nr = 0x1234;
+    uint32_t serial_nr = info->serial ? atoi(info->serial) : 0;
+    *(uint16_t *)(edid +  8) = cpu_to_be16(vendor_id);
+    *(uint16_t *)(edid + 10) = cpu_to_le16(model_nr);
+    *(uint32_t *)(edid + 12) = cpu_to_le32(serial_nr);
+
+    /* manufacture week and year */
+    edid[16] = 42;
+    edid[17] = 2014 - 1990;
+
+    /* edid version */
+    edid[18] = 1;
+    edid[19] = 4;
+
+
+    /* =============== basic display parameters =============== */
+
+    /* video input: digital, 8bpc, displayport */
+    edid[20] = 0xa5;
+
+    /* screen size: undefined */
+    edid[21] = info->prefx * info->dpi / 2540;
+    edid[22] = info->prefy * info->dpi / 2540;
+
+    /* display gamma: 2.2 */
+    edid[23] = 220 - 100;
+
+    /* supported features bitmap: std sRGB, preferred timing */
+    edid[24] = 0x06;
+
+
+    /* =============== chromaticity coordinates =============== */
+
+    /* standard sRGB colorspace */
+    edid_colorspace(edid,
+                    0.6400, 0.3300,   /* red   */
+                    0.3000, 0.6000,   /* green */
+                    0.1500, 0.0600,   /* blue  */
+                    0.3127, 0.3290);  /* white point  */
+
+    /* =============== established timing bitmap =============== */
+    /* =============== standard timing information =============== */
+
+    /* both filled by edid_fill_modes() */
+
+
+    /* =============== descriptor blocks =============== */
+
+    edid_desc_timing(edid + desc, info->prefx, info->prefy, info->dpi);
+    desc += 18;
+
+    edid_desc_ranges(edid + desc);
+    desc += 18;
+
+    if (info->name) {
+        edid_desc_text(edid + desc, 0xfc, info->name);
+        desc += 18;
+    }
+
+    if (info->serial) {
+        edid_desc_text(edid + desc, 0xff, info->serial);
+        desc += 18;
+    }
+
+    if (desc < 126) {
+        xtra3 = edid + desc;
+        edid_desc_xtra3_std(xtra3);
+        desc += 18;
+    }
+
+    while (desc < 126) {
+        edid_desc_dummy(edid + desc);
+        desc += 18;
+    }
+
+    /* =============== finish up =============== */
+
+    edid_fill_modes(edid, xtra3, dta, info->maxx, info->maxy);
+    edid_checksum(edid);
+    if (dta) {
+        edid_checksum(dta);
+    }
+}