Document amd64 platform-specific code

kernel/amd64/io.c

@@ -1,42 +1,51 @@
 #include <amd64/io.h>
 #include <libk/std.h>
 
+/// Perform outb instruction (send 8-bit int)
 void amd64_io_outb (uint16_t port, uint8_t v) {
   __asm__ volatile ("outb %1, %0" ::"dN"(port), "a"(v));
 }
 
+/// Perform outw instruction (send 16-bit int)
 void amd64_io_outw (uint16_t port, uint16_t v) {
   __asm__ volatile ("outw %%ax, %%dx" ::"a"(v), "d"(port));
 }
 
+/// Perform outl instruction (send 32-bit int)
 void amd64_io_outl (uint16_t port, uint32_t v) {
   __asm__ volatile ("outl %%eax, %%dx" ::"d"(port), "a"(v));
 }
 
+/// Perform outsw instruction (send a string)
 void amd64_io_outsw (uint16_t port, const void* addr, int cnt) {
   __asm__ volatile ("cld; rep outsw" : "+S"(addr), "+c"(cnt) : "d"(port) : "memory", "cc");
 }
 
+/// Perform inb instruction (receive 8-bit int)
 uint8_t amd64_io_inb (uint16_t port) {
   uint8_t r;
   __asm__ volatile ("inb %1, %0" : "=a"(r) : "dN"(port));
   return r;
 }
 
+/// Perform inw instruction (receive 16-bit int)
 uint16_t amd64_io_inw (uint16_t port) {
   uint16_t r;
   __asm__ volatile ("inw %%dx, %%ax" : "=a"(r) : "d"(port));
   return r;
 }
 
+/// Perform inl instruction (receive 32-bit int)
 uint32_t amd64_io_inl (uint16_t port) {
   uint32_t r;
   __asm__ volatile ("inl %%dx, %%eax" : "=a"(r) : "d"(port));
   return r;
 }
 
+/// Perform insw instruction (receive a string)
 void amd64_io_insw (uint16_t port, void* addr, int cnt) {
   __asm__ volatile ("cld; rep insw" : "+D"(addr), "+c"(cnt) : "d"(port) : "memory", "cc");
 }
 
+/// output a byte on port 0x80, which does a small IO delay
 void amd64_io_wait (void) { amd64_io_outb (0x80, 0); }