Doc updates

module_usb_audio/usb_buffer/xc_ptr.h

@@ -0,0 +1,34 @@
+#ifndef __xc_ptr__
+#define __xc_ptr__
+
+typedef unsigned int xc_ptr;
+
+// Note that this function is marked as const to avoid the XC
+// parallel usage checks, this is only really going to work if this
+// is the *only* way the array a is accessed (and everything else uses
+// the xc_ptr)
+inline xc_ptr array_to_xc_ptr(const unsigned a[])
+{
+  xc_ptr x;
+  asm("mov %0, %1":"=r"(x):"r"(a));
+  return x;
+}
+
+#define write_via_xc_ptr(p,x)   asm("stw %0, %1[0]"::"r"(x),"r"(p))
+
+#define write_via_xc_ptr_indexed(p,i,x)   asm("stw %0, %1[%2]"::"r"(x),"r"(p),"r"(i))
+#define write_byte_via_xc_ptr_indexed(p,i,x)   asm("st8 %0, %1[%2]"::"r"(x),"r"(p),"r"(i))
+// No immediate st8 format
+#define write_byte_via_xc_ptr(p,x)   write_byte_via_xc_ptr_indexed(p, 0, x)
+
+#define read_via_xc_ptr(x,p)  asm("ldw %0, %1[0]":"=r"(x):"r"(p));
+
+#define read_via_xc_ptr_indexed(x,p,i)  asm("ldw %0, %1[%2]":"=r"(x):"r"(p),"r"(i));
+#define read_byte_via_xc_ptr_indexed(x,p,i)  asm("ld8u %0, %1[%2]":"=r"(x):"r"(p),"r"(i));
+// No immediate ld8u format
+#define read_byte_via_xc_ptr(x,p)  read_byte_via_xc_ptr_indexed(x, p, 0)
+
+#define GET_SHARED_GLOBAL(x, g) asm("ldw %0, dp[" #g "]":"=r"(x))
+#define SET_SHARED_GLOBAL(g, v) asm("stw %0, dp[" #g "]"::"r"(v))
+
+#endif