kdrive: add OS/platform callback for screen enable/disable

New OS/platform callbacks that are called when screens are enabled
or disabled. This allows individual Kdrive implementations to take
specific action, eg. configure/reset graphics hardware.

Signed-off-by: stefan11111 <stefan11111@shitposting.expert>
Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>

hw/kdrive/src/kdrive.c

@@ -154,6 +154,8 @@ static void
 KdDisableScreens(void)
 {
     KdSuspend();
+    if (kdEnabled && (kdOsFuncs->Disable))
+        kdOsFuncs->Disable();
     kdEnabled = FALSE;
 }
 
@@ -604,6 +606,8 @@ Bool KdCloseScreen(ScreenPtr pScreen)
          * Clean up OS when last card is closed
          */
         if (card == kdCardInfo) {
+            if (kdEnabled && (kdOsFuncs->Disable))
+                kdOsFuncs->Disable();
             kdEnabled = FALSE;
         }
     }
@@ -818,6 +822,8 @@ KdScreenInit(ScreenPtr pScreen, int argc, char **argv)
     /*
      * Enable the hardware
      */
+    if ((!kdEnabled) && (kdOsFuncs->Enable))
+        kdOsFuncs->Enable();
     kdEnabled = TRUE;
 
     if (screen->mynum == card->selected) {

hw/kdrive/src/kdrive.h

@@ -280,9 +280,9 @@ void KdRemoveKeyboard(KdKeyboardInfo * ki);
 
 typedef struct _KdOsFuncs {
     int (*Init) (void); /* Only called when the X server is started, when serverGeneration == 1 */
-    void (*Enable) (void);
+    void (*Enable) (void);        /* called when screen is enabled */
+    void (*Disable) (void);       /* called when screen is disabled */
     Bool (*SpecialKey) (KeySym);
-    void (*Disable) (void);
     void (*Fini) (void);
     void (*pollEvents) (void);
     void (*Bell) (int, int, int); /* if not NULL called instead of the keyboard driver's function */