vid_mga: Implement DDC on the Millennium

src/include/86box/vid_svga.h

@@ -398,6 +398,7 @@ extern uint8_t tvp3026_ramdac_in(uint16_t addr, int rs2, int rs3, void *priv, sv
 extern void    tvp3026_recalctimings(void *priv, svga_t *svga);
 extern void    tvp3026_hwcursor_draw(svga_t *svga, int displine);
 extern float   tvp3026_getclock(int clock, void *priv);
+extern void    tvp3026_gpio(uint8_t (*read)(uint8_t cntl, void *priv), void (*write)(uint8_t cntl, uint8_t data, void *priv), void *cb_priv, void *priv);
 
 #    ifdef EMU_DEVICE_H
 extern const device_t ati68860_ramdac_device;

src/video/vid_mga.c

@@ -5314,6 +5314,27 @@ mystique_hwcursor_draw(svga_t *svga, int displine)
         svga->hwcursor_latch.addr += 16;
 }
 
+static uint8_t
+mystique_tvp3026_gpio_read(uint8_t cntl, void *priv)
+{
+    mystique_t *mystique = (mystique_t *) priv;
+
+    uint8_t ret = 0xff;
+    if (!i2c_gpio_get_scl(mystique->i2c_ddc))
+        ret &= ~0x10;
+    if (!i2c_gpio_get_sda(mystique->i2c_ddc))
+        ret &= ~0x04;
+    return ret;
+}
+
+static void
+mystique_tvp3026_gpio_write(uint8_t cntl, uint8_t data, void *priv)
+{
+    mystique_t *mystique = (mystique_t *) priv;
+
+    i2c_gpio_set(mystique->i2c_ddc, !(cntl & 0x10) || (data & 0x10), !(cntl & 0x04) || (data & 0x04));
+}
+
 static uint8_t
 mystique_pci_read(UNUSED(int func), int addr, void *priv)
 {
@@ -5625,6 +5646,7 @@ mystique_init(const device_t *info)
         mystique->svga.ramdac            = device_add(&tvp3026_ramdac_device);
         mystique->svga.clock_gen         = mystique->svga.ramdac;
         mystique->svga.getclock          = tvp3026_getclock;
+        tvp3026_gpio(mystique_tvp3026_gpio_read, mystique_tvp3026_gpio_write, mystique, mystique->svga.ramdac);
     } else {
         video_inform(VIDEO_FLAG_TYPE_SPECIAL, &timing_matrox_mystique);
         svga_init(info, &mystique->svga, mystique, mystique->vram_size << 20,

src/video/vid_tvp3026_ramdac.c

@@ -55,6 +55,11 @@ typedef struct tvp3026_ramdac_t {
         uint8_t n;
         uint8_t p;
     } pix, mem, loop;
+    uint8_t   gpio_cntl;
+    uint8_t   gpio_data;
+    uint8_t (*gpio_read)(uint8_t cntl, void *priv);
+    void    (*gpio_write)(uint8_t cntl, uint8_t val, void *priv);
+    void     *gpio_priv;
 } tvp3026_ramdac_t;
 
 static void
@@ -211,6 +216,16 @@ tvp3026_ramdac_out(uint16_t addr, int rs2, int rs3, uint8_t val, void *priv, svg
                     ramdac->misc      = val;
                     svga->ramdac_type = (val & 0x08) ? RAMDAC_8BIT : RAMDAC_6BIT;
                     break;
+                case 0x2a: /* General-Purpose I/O Control */
+                    ramdac->gpio_cntl = val;
+                    if (ramdac->gpio_write)
+                        ramdac->gpio_write(ramdac->gpio_cntl, ramdac->gpio_data, ramdac->gpio_priv);
+                    break;
+                case 0x2b: /* General-Purpose I/O Data */
+                    ramdac->gpio_data = val;
+                    if (ramdac->gpio_write)
+                        ramdac->gpio_write(ramdac->gpio_cntl, ramdac->gpio_data, ramdac->gpio_priv);
+                    break;
                 case 0x2c: /* PLL Address */
                     ramdac->pll_addr = val;
                     break;
@@ -389,6 +404,16 @@ tvp3026_ramdac_in(uint16_t addr, int rs2, int rs3, void *priv, svga_t *svga)
                 case 0x1e: /* Miscellaneous Control */
                     temp = ramdac->misc;
                     break;
+                case 0x2a: /* General-Purpose I/O Control */
+                    temp = ramdac->gpio_cntl;
+                    break;
+                case 0x2b: /* General-Purpose I/O Data */
+                    if (ramdac->gpio_read) {
+                        temp = 0xe0 | (ramdac->gpio_cntl & 0x1f); /* keep upper bits untouched */
+                        ramdac->gpio_data = (ramdac->gpio_data & temp) | (ramdac->gpio_read(ramdac->gpio_cntl, ramdac->gpio_priv) & ~temp);
+                    }
+                    temp = ramdac->gpio_data;
+                    break;
                 case 0x2c: /* PLL Address */
                     temp = ramdac->pll_addr;
                     break;
@@ -630,6 +655,18 @@ tvp3026_getclock(int clock, void *priv)
     return f_pll;
 }
 
+void
+tvp3026_gpio(uint8_t (*read)(uint8_t cntl, void *priv),
+             void (*write)(uint8_t cntl, uint8_t val, void *priv),
+             void *cb_priv, void *priv)
+{
+    tvp3026_ramdac_t *ramdac = (tvp3026_ramdac_t *) priv;
+
+    ramdac->gpio_read  = read;
+    ramdac->gpio_write = write;
+    ramdac->gpio_priv  = cb_priv;
+}
+
 void *
 tvp3026_ramdac_init(const device_t *info)
 {