edid: use physical dimensions if available

Replace dpi with width_mm/height_mm in qemu_edid_info.

Use it when set (non-zero) to compute the DPI and generate the EDID.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20200927145751.365446-3-marcandre.lureau@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/display/edid-generate.c

@@ -205,12 +205,8 @@ static void edid_desc_dummy(uint8_t *desc)
 
 static void edid_desc_timing(uint8_t *desc,
                              uint32_t xres, uint32_t yres,
-                             uint32_t dpi)
+                             uint32_t xmm, uint32_t ymm)
 {
-    /* physical display size */
-    uint32_t xmm = xres * 254 / 10 / dpi;
-    uint32_t ymm = yres * 254 / 10 / dpi;
-
     /* pull some realistic looking timings out of thin air */
     uint32_t xfront = xres * 25 / 100;
     uint32_t xsync  = xres *  3 / 100;
@@ -290,12 +286,24 @@ static void edid_colorspace(uint8_t *edid,
     edid[34] = white_y >> 2;
 }
 
+static uint32_t qemu_edid_dpi_from_mm(uint32_t mm, uint32_t res)
+{
+    return res * 254 / 10 / mm;
+}
+
+uint32_t qemu_edid_dpi_to_mm(uint32_t dpi, uint32_t res)
+{
+    return res * 254 / 10 / dpi;
+}
+
 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;
+    uint32_t width_mm, height_mm;
+    uint32_t dpi = 100; /* if no width_mm/height_mm */
 
     /* =============== set defaults  =============== */
 
@@ -305,15 +313,20 @@ void qemu_edid_generate(uint8_t *edid, size_t size,
     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;
     }
+    if (info->width_mm && info->height_mm) {
+        width_mm = info->width_mm;
+        height_mm = info->height_mm;
+        dpi = qemu_edid_dpi_from_mm(width_mm, info->prefx);
+    } else {
+        width_mm = qemu_edid_dpi_to_mm(dpi, info->prefx);
+        height_mm = qemu_edid_dpi_to_mm(dpi, info->prefy);
+    }
 
     /* =============== extensions  =============== */
 
@@ -360,8 +373,8 @@ void qemu_edid_generate(uint8_t *edid, size_t size,
     edid[20] = 0xa5;
 
     /* screen size: undefined */
-    edid[21] = info->prefx * 254 / 100 / info->dpi;
-    edid[22] = info->prefy * 254 / 100 / info->dpi;
+    edid[21] = width_mm / 10;
+    edid[22] = height_mm / 10;
 
     /* display gamma: 2.2 */
     edid[23] = 220 - 100;
@@ -387,7 +400,8 @@ void qemu_edid_generate(uint8_t *edid, size_t size,
 
     /* =============== descriptor blocks =============== */
 
-    edid_desc_timing(edid + desc, info->prefx, info->prefy, info->dpi);
+    edid_desc_timing(edid + desc, info->prefx, info->prefy,
+                     width_mm, height_mm);
     desc += 18;
 
     edid_desc_ranges(edid + desc);

include/hw/display/edid.h

@@ -5,7 +5,8 @@ typedef struct qemu_edid_info {
     const char *vendor; /* http://www.uefi.org/pnp_id_list */
     const char *name;
     const char *serial;
-    uint32_t    dpi;
+    uint16_t    width_mm;
+    uint16_t    height_mm;
     uint32_t    prefx;
     uint32_t    prefy;
     uint32_t    maxx;
@@ -18,6 +19,8 @@ size_t qemu_edid_size(uint8_t *edid);
 void qemu_edid_region_io(MemoryRegion *region, Object *owner,
                          uint8_t *edid, size_t size);
 
+uint32_t qemu_edid_dpi_to_mm(uint32_t dpi, uint32_t res);
+
 #define DEFINE_EDID_PROPERTIES(_state, _edid_info)              \
     DEFINE_PROP_UINT32("xres", _state, _edid_info.prefx, 0),    \
     DEFINE_PROP_UINT32("yres", _state, _edid_info.prefy, 0),    \

qemu-edid.c

@@ -9,7 +9,10 @@
 #include "qemu/cutils.h"
 #include "hw/display/edid.h"
 
-static qemu_edid_info info;
+static qemu_edid_info info = (qemu_edid_info) {
+    .prefx = 1024,
+    .prefy = 768,
+};
 
 static void usage(FILE *out)
 {
@@ -39,6 +42,7 @@ int main(int argc, char *argv[])
 {
     FILE *outfile = NULL;
     uint8_t blob[256];
+    uint32_t dpi = 100;
     int rc;
 
     for (;;) {
@@ -83,7 +87,7 @@ int main(int argc, char *argv[])
             }
             break;
         case 'd':
-            if (qemu_strtoui(optarg, NULL, 10, &info.dpi) < 0) {
+            if (qemu_strtoui(optarg, NULL, 10, &dpi) < 0) {
                 fprintf(stderr, "not a number: %s\n", optarg);
                 exit(1);
             }
@@ -110,6 +114,9 @@ int main(int argc, char *argv[])
         outfile = stdout;
     }
 
+    info.width_mm = qemu_edid_dpi_to_mm(dpi, info.prefx);
+    info.height_mm = qemu_edid_dpi_to_mm(dpi, info.prefy);
+
     memset(blob, 0, sizeof(blob));
     qemu_edid_generate(blob, sizeof(blob), &info);
     fwrite(blob, sizeof(blob), 1, outfile);