modesetting: attempt to work out if we want 24 or 32bpp

the cirrus driver presents certain challenges, and this is a
workaround, until we can possibly agree some sane interface
for exposing this information.

Signed-off-by: Dave Airlie <airlied@redhat.com>

hw/xfree86/drivers/modesetting/driver.c

@@ -59,10 +59,6 @@
 
 #include "driver.h"
 
-#ifndef DRM_CAP_DUMB_PREFER_SHADOW
-#define DRM_CAP_DUMB_PREFER_SHADOW 4
-#endif
-
 static void AdjustFrame(int scrnIndex, int x, int y, int flags);
 static Bool CloseScreen(int scrnIndex, ScreenPtr pScreen);
 static Bool EnterVT(int scrnIndex, int flags);
@@ -397,6 +393,8 @@ PreInit(ScrnInfoPtr pScrn, int flags)
     Bool prefer_shadow = TRUE;
     uint64_t value = 0;
     int ret;
+    int bppflags;
+    int defaultdepth, defaultbpp;
 
     if (pScrn->numEntities != 1)
 	return FALSE;
@@ -459,9 +457,16 @@ PreInit(ScrnInfoPtr pScrn, int flags)
     if (ms->fd < 0)
 	return FALSE;
 
+    ms->drmmode.fd = ms->fd;
+
+    drmmode_get_default_bpp(pScrn, &ms->drmmode, &defaultdepth, &defaultbpp);
+    if (defaultdepth == 24 && defaultbpp == 24)
+	    bppflags = Support24bppFb;
+    else
+	    bppflags = PreferConvert24to32 | SupportConvert24to32 | Support32bppFb;
+    
     if (!xf86SetDepthBpp
-	(pScrn, 0, 0, 0,
+	(pScrn, defaultdepth, defaultdepth, defaultbpp, bppflags))
-	 PreferConvert24to32 | SupportConvert24to32 | Support32bppFb))
 	return FALSE;
 
     switch (pScrn->depth) {
@@ -501,7 +506,6 @@ PreInit(ScrnInfoPtr pScrn, int flags)
     ms->drmmode.shadow_enable = xf86ReturnOptValBool(ms->Options, OPTION_SHADOW_FB, prefer_shadow);
 
     xf86DrvMsg(pScrn->scrnIndex, X_INFO, "ShadowFB: preferred %s, enabled %s\n", prefer_shadow ? "YES" : "NO", ms->drmmode.shadow_enable ? "YES" : "NO");
-    ms->drmmode.fd = ms->fd;
     if (drmmode_pre_init(pScrn, &ms->drmmode, pScrn->bitsPerPixel / 8) == FALSE) {
 	xf86DrvMsg(pScrn->scrnIndex, X_ERROR, "KMS setup failed\n");
 	goto fail;

hw/xfree86/drivers/modesetting/drmmode_display.c

@@ -1355,3 +1355,50 @@ void drmmode_free_bos(ScrnInfoPtr pScrn, drmmode_ptr drmmode)
 		dumb_bo_destroy(drmmode->fd, drmmode_crtc->cursor_bo);
 	}
 }
+
+/* ugly workaround to see if we can create 32bpp */
+void drmmode_get_default_bpp(ScrnInfoPtr pScrn, drmmode_ptr drmmode, int *depth, int *bpp)
+{
+	drmModeResPtr mode_res;
+	uint64_t value;
+	struct dumb_bo *bo;
+	uint32_t fb_id;
+	int ret;
+
+	/* 16 is fine */
+	ret = drmGetCap(drmmode->fd, DRM_CAP_DUMB_PREFERRED_DEPTH, &value);
+	if (!ret && (value == 16 || value == 8)) {
+		*depth = value;
+		*bpp = value;
+		return;
+	}
+
+	*depth = 24;
+	mode_res = drmModeGetResources(drmmode->fd);
+	if (!mode_res)
+		return;
+
+	/*create a bo */
+	bo = dumb_bo_create(drmmode->fd, mode_res->min_width, mode_res->min_height, 32);
+	if (!bo) {
+		*bpp = 24;
+		goto out;
+	}
+
+	ret = drmModeAddFB(drmmode->fd, mode_res->min_width, mode_res->min_height,
+			    24, 32, bo->pitch, bo->handle, &fb_id);
+
+	if (ret) {
+		*bpp = 24;
+		dumb_bo_destroy(drmmode->fd, bo);
+		goto out;
+	}
+
+	drmModeRmFB(drmmode->fd, fb_id);
+	*bpp = 32;
+
+	dumb_bo_destroy(drmmode->fd, bo);
+out:	
+	drmModeFreeResources(mode_res);
+	return;
+}

hw/xfree86/drivers/modesetting/drmmode_display.h

@@ -103,4 +103,14 @@ Bool drmmode_create_initial_bos(ScrnInfoPtr pScrn, drmmode_ptr drmmode);
 void *drmmode_map_front_bo(drmmode_ptr drmmode);
 Bool drmmode_map_cursor_bos(ScrnInfoPtr pScrn, drmmode_ptr drmmode);
 void drmmode_free_bos(ScrnInfoPtr pScrn, drmmode_ptr drmmode);
+void drmmode_get_default_bpp(ScrnInfoPtr pScrn, drmmode_ptr drmmmode, int *depth, int *bpp);
+
+#ifndef DRM_CAP_DUMB_PREFERRED_DEPTH
+#define DRM_CAP_DUMB_PREFERRED_DEPTH 3
+#endif
+#ifndef DRM_CAP_DUMB_PREFER_SHADOW
+#define DRM_CAP_DUMB_PREFER_SHADOW 4
+#endif
+
+
 #endif