nes: Expose and document all joypad keys

doc/nes.sgml

@@ -123,6 +123,14 @@ No extended memory drivers are currently available for the NES.
 
 </descrip><p>
 
+The generic interface doesn't export the start and select buttons. To
+test for those, use the defines in nes.h instead of the generic masks.
+
+Example:
+<tscreen><verb>
+if (joy_read(0) & KEY_A)
+</verb></tscreen>
+
 
 <sect1>Mouse drivers<p>
 

include/nes.h

@@ -90,6 +90,15 @@
 /* No support for dynamically loadable drivers */
 #define DYN_DRV         0
 
+/* The joystick keys - all keys are supported */
+#define KEY_UP		0x10
+#define KEY_DOWN	0x20
+#define KEY_LEFT	0x40
+#define KEY_RIGHT	0x80
+#define KEY_A		0x1
+#define KEY_B		0x2
+#define KEY_SELECT	0x4
+#define KEY_START	0x8
 
 
 /* The addresses of the static drivers */