xfree86: Immediately handle failure to set HW cursor, v5

Based on v4 by Alexandre Courbot <acourbot@nvidia.com>

There is currently no reliable way to report failure to set a HW
cursor. Still such failures can happen if e.g. the MODE_CURSOR DRM
ioctl fails (which currently happens at least with modesetting on Tegra
for format incompatibility reasons).

As failures are currently handled by setting the HW cursor size to
(0,0), the fallback to SW cursor will not happen until the next time the
cursor changes and xf86CursorSetCursor() is called again. In the
meantime, the cursor will be invisible to the user.

This patch addresses that by adding _xf86CrtcFuncs::set_cursor_check and
_xf86CursorInfoRec::ShowCursorCheck hook variants that return booleans.
This allows to propagate errors up to xf86CursorSetCursor(), which can
then fall back to using the SW cursor immediately.

v5: Updated the patch to apply to current git HEAD, split up into two
patches (server and modesetting driver) and adjusted the code slightly
to match surrounding code.  I also removed the new exported function
ShowCursorCheck(), as instead just changing ShowCursor() to return Bool
should not affect its current callers.

Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Michael Thayer <michael.thayer@oracle.com>

hw/xfree86/modes/xf86Crtc.h

@@ -195,6 +195,8 @@ typedef struct _xf86CrtcFuncs {
      */
     void
      (*show_cursor) (xf86CrtcPtr crtc);
+    Bool
+     (*show_cursor_check) (xf86CrtcPtr crtc);
 
     /**
      * Hide cursor
@@ -993,7 +995,7 @@ static _X_INLINE _X_DEPRECATED void xf86_reload_cursors(ScreenPtr screen) {}
 /**
  * Called from EnterVT to turn the cursors back on
  */
-extern _X_EXPORT void
+extern _X_EXPORT Bool
  xf86_show_cursors(ScrnInfoPtr scrn);
 
 /**

hw/xfree86/modes/xf86Cursors.c

@@ -210,8 +210,14 @@ set_bit(CARD8 *image, xf86CursorInfoPtr cursor_info, int x, int y, Bool mask)
 
 /*
  * Wrappers to deal with API compatibility with drivers that don't expose
- * load_cursor_*_check
+ * *_cursor_*_check
  */
+static inline Bool
+xf86_driver_has_show_cursor(xf86CrtcPtr crtc)
+{
+    return crtc->funcs->show_cursor_check || crtc->funcs->show_cursor;
+}
+
 static inline Bool
 xf86_driver_has_load_cursor_image(xf86CrtcPtr crtc)
 {
@@ -224,6 +230,15 @@ xf86_driver_has_load_cursor_argb(xf86CrtcPtr crtc)
     return crtc->funcs->load_cursor_argb_check || crtc->funcs->load_cursor_argb;
 }
 
+static inline Bool
+xf86_driver_show_cursor(xf86CrtcPtr crtc)
+{
+    if (crtc->funcs->show_cursor_check)
+        return crtc->funcs->show_cursor_check(crtc);
+    crtc->funcs->show_cursor(crtc);
+    return TRUE;
+}
+
 static inline Bool
 xf86_driver_load_cursor_image(xf86CrtcPtr crtc, CARD8 *cursor_image)
 {
@@ -333,16 +348,19 @@ xf86_hide_cursors(ScrnInfoPtr scrn)
     }
 }
 
-static void
+static Bool
 xf86_crtc_show_cursor(xf86CrtcPtr crtc)
 {
-    if (!crtc->cursor_shown && crtc->cursor_in_range) {
-        crtc->funcs->show_cursor(crtc);
-        crtc->cursor_shown = TRUE;
-    }
+    if (!crtc->cursor_in_range)
+        return TRUE;
+
+    if (!crtc->cursor_shown)
+        crtc->cursor_shown = xf86_driver_show_cursor(crtc);
+
+    return crtc->cursor_shown;
 }
 
-void
+Bool
 xf86_show_cursors(ScrnInfoPtr scrn)
 {
     xf86CrtcConfigPtr xf86_config = XF86_CRTC_CONFIG_PTR(scrn);
@@ -352,9 +370,11 @@ xf86_show_cursors(ScrnInfoPtr scrn)
     for (c = 0; c < xf86_config->num_crtc; c++) {
         xf86CrtcPtr crtc = xf86_config->crtc[c];
 
-        if (crtc->enabled)
-            xf86_crtc_show_cursor(crtc);
+        if (crtc->enabled && !xf86_crtc_show_cursor(crtc))
+            return FALSE;
     }
+
+    return TRUE;
 }
 
 static void
@@ -653,7 +673,7 @@ xf86_cursors_init(ScreenPtr screen, int max_width, int max_height, int flags)
     cursor_info->SetCursorPosition = xf86_set_cursor_position;
     cursor_info->LoadCursorImageCheck = xf86_load_cursor_image;
     cursor_info->HideCursor = xf86_hide_cursors;
-    cursor_info->ShowCursor = xf86_show_cursors;
+    cursor_info->ShowCursorCheck = xf86_show_cursors;
     cursor_info->UseHWCursor = xf86_use_hw_cursor;
     if (flags & HARDWARE_CURSOR_ARGB) {
         cursor_info->UseHWCursorARGB = xf86_use_hw_cursor_argb;

hw/xfree86/ramdac/xf86Cursor.h

@@ -16,6 +16,7 @@ typedef struct _xf86CursorInfoRec {
     Bool (*LoadCursorImageCheck) (ScrnInfoPtr pScrn, unsigned char *bits);
     void (*HideCursor) (ScrnInfoPtr pScrn);
     void (*ShowCursor) (ScrnInfoPtr pScrn);
+    Bool (*ShowCursorCheck) (ScrnInfoPtr pScrn);
     unsigned char *(*RealizeCursor) (struct _xf86CursorInfoRec *, CursorPtr);
     Bool (*UseHWCursor) (ScreenPtr, CursorPtr);
 
@@ -40,6 +41,21 @@ xf86DriverLoadCursorImage(xf86CursorInfoPtr infoPtr, unsigned char *bits)
     return TRUE;
 }
 
+static inline Bool
+xf86DriverHasShowCursor(xf86CursorInfoPtr infoPtr)
+{
+    return infoPtr->ShowCursorCheck || infoPtr->ShowCursor;
+}
+
+static inline Bool
+xf86DriverShowCursor(xf86CursorInfoPtr infoPtr)
+{
+    if(infoPtr->ShowCursorCheck)
+        return infoPtr->ShowCursorCheck(infoPtr->pScrn);
+    infoPtr->ShowCursor(infoPtr->pScrn);
+    return TRUE;
+}
+
 static inline Bool
 xf86DriverHasLoadCursorARGB(xf86CursorInfoPtr infoPtr)
 {

hw/xfree86/ramdac/xf86HWCurs.c

@@ -93,7 +93,8 @@ xf86InitHardwareCursor(ScreenPtr pScreen, xf86CursorInfoPtr infoPtr)
     if (!infoPtr->SetCursorPosition ||
         !xf86DriverHasLoadCursorImage(infoPtr) ||
         !infoPtr->HideCursor ||
-        !infoPtr->ShowCursor || !infoPtr->SetCursorColors)
+        !xf86DriverHasShowCursor(infoPtr) ||
+        !infoPtr->SetCursorColors)
         return FALSE;
 
     if (infoPtr->RealizeCursor) {
@@ -224,8 +225,7 @@ xf86ScreenSetCursor(ScreenPtr pScreen, CursorPtr pCurs, int x, int y)
 
     (*infoPtr->SetCursorPosition) (infoPtr->pScrn, x, y);
 
-    (*infoPtr->ShowCursor) (infoPtr->pScrn);
-    return TRUE;
+    return xf86DriverShowCursor(infoPtr);
 }
 
 Bool
@@ -287,7 +287,7 @@ xf86SetTransparentCursor(ScreenPtr pScreen)
         xf86DriverLoadCursorImage (infoPtr,
                                    ScreenPriv->transparentData);
 
-    (*infoPtr->ShowCursor) (infoPtr->pScrn);
+    xf86DriverShowCursor(infoPtr);
 
     input_unlock();
 }