16-bit depth on radeonfb

Inspired by:

On Tue, Jul 28, 2026 at 02:23:29PM +0200, Edgar Fuß wrote:
> I find nothing wrong with proposing a patch, finding out that nobody else 
> finds it useful and so keeping it local. /Not/ proposing it prevents others 
> from finding it useful and the patch getting incorporated.

16-bit depth makes hardware with limited memory and/or memory bandwidth
much more usable and useful. The following patch adds this to radeonfb.

--- ./dev/pci/radeonfb.c.orig
+++ ./dev/pci/radeonfb.c
@@ -104,7 +104,8 @@
 #ifdef RADEONFB_DEPTH_32
 #define RADEONFB_DEFAULT_DEPTH 32
 #else
-#define RADEONFB_DEFAULT_DEPTH 8
+/* #define RADEONFB_DEFAULT_DEPTH 8 */
+#define RADEONFB_DEFAULT_DEPTH 16
 #endif
 
 static int radeonfb_match(device_t, cfdata_t, void *);
@@ -214,7 +215,7 @@
 
 #ifndef	RADEON_DEFAULT_MODE
 /* any reasonably modern display should handle this */
-#define	RADEON_DEFAULT_MODE	"1024x768x60"
+#define	RADEON_DEFAULT_MODE	"1024x768x60" /* to use when edid fails */
 #endif
 
 extern const u_char rasops_cmap[768];
@@ -897,6 +898,9 @@
 		case 8:
 			dp->rd_format = 2;
 			break;
+		case 16:
+			dp->rd_format = 4;
+			break;
 		case 32:
 			dp->rd_format = 6;
 			break;
@@ -2379,7 +2383,7 @@
 	/*
 	 * CRTC_GEN_CNTL - depth, accelerator mode, etc.
 	 */
-	/* only bother with 32bpp and 8bpp */
+	/* only bother with 32bpp, 16bpp, 8bpp */
 	v = dp->rd_format << RADEON_CRTC_PIX_WIDTH_SHIFT;
 
 	if (crtc == 1) {

Cheers
/od2uvb