Separate kernel code from test code

Eventually I want the kernel to be loaded from the SD card as well, but
it still needs to separate from user programs.

At some point there should be a folder just for the BIOS, which should
read from the boot block of the SD card and start executing, and thats
it.

sw/kernel/devices/sd_card.c

@@ -0,0 +1,75 @@
+#include <stdint.h>
+#include <conio.h>
+
+#include "devices/sd_card.h"
+
+void sd_init() {
+	uint32_t resp;
+	sd_card_command(0, 0);
+
+	sd_card_command(0x000001aa, 8);
+	sd_card_resp(&resp);
+	//cprintf("CMD8: %lx\n", resp);
+
+	sd_card_command(0, 55);
+	sd_card_command(0x40180000, 41);
+	sd_card_resp(&resp);
+	//cprintf("CMD41: %lx\n", resp);
+
+	sd_card_command(0, 55);
+	sd_card_command(0x40180000, 41);
+	sd_card_resp(&resp);
+	//cprintf("CMD41: %lx\n", resp);
+
+	sd_card_command(0, 2);
+	sd_card_resp(&resp);
+	//cprintf("CMD2: %lx\n", resp);
+}
+
+uint16_t sd_get_rca() {
+	uint32_t resp;
+
+	sd_card_command(0, 3);
+	resp = 0;
+	sd_card_resp(&resp);
+
+	//cprintf("CMD3: %lx\n", resp);
+
+	return resp >> 16;
+}
+
+uint16_t sd_select_card(uint16_t rca) {
+	uint32_t resp;
+
+	sd_card_command((uint32_t)rca << 16, 7);
+	sd_card_resp(&resp);
+
+	return (uint16_t) resp;
+}
+
+uint16_t sd_get_status(uint16_t rca) {
+	uint32_t resp;
+
+	sd_card_command((uint32_t)rca << 16, 13);
+	sd_card_resp(&resp);
+
+	return (uint16_t) resp;
+}
+
+void sd_readblock(uint32_t addr, void* buf) {
+	uint32_t resp;
+	int i;
+
+	sd_card_command(addr, 17);
+	sd_card_resp(&resp);
+	//cprintf("CMD17: %lx\n", resp);
+
+	sd_card_wait_for_data();
+
+	//cprintf("Read data: \n");
+	for (i = 0; i < 512; i++){
+		((uint8_t*)buf)[i] = sd_card_read_byte();
+	}
+
+	//cprintf("\n");
+}