Push minimally working FATFS.

fusee/fusee-primary/src/sd_utils.c

@@ -1,11 +1,54 @@
 #include "sd_utils.h"
+#include "hwinit.h"
+#include "sdmmc.h"
+#include "lib/printk.h"
+#include "ff.h"
+
+/* This is used by diskio.h. */
+struct mmc sd_mmc;
+FATFS sd_fs;
+static int initialized_sd = 0;
+static int mounted_sd = 0;
+
+int initialize_sd(void) {
+    if (initialized_sd) {
+        return 1;
+    }
+    mc_enable_ahb_redirect();
+    if (sdmmc_init(&sd_mmc, SWITCH_MICROSD) == 0) {
+        printk("Initialized SD card!\n");
+        initialized_sd = 1;
+    }
+    return initialized_sd;
+}
+
+int mount_sd(void) {
+    if (mounted_sd) {
+        return 1;
+    }
+    if (f_mount(&sd_fs, "", 1) == FR_OK) {
+        printk("Mounted SD card!\n");
+        mounted_sd = 1;
+    }
+    return mounted_sd;
+}
 
 size_t read_sd_file(void *dst, size_t dst_size, const char *filename) {
-    /* TODO: Implement this function. */
-    (void)(dst);
-    (void)(dst_size);
-    (void)(filename);
+    if (!initialized_sd && initialize_sd() == 0) {
+        return 0;
+    }
+    if (!mounted_sd && mount_sd() == 0) {
+        return 0;
+    }
     
-    /* Fail, because this function is unimplemented. */
-    return 0;
+    FIL f;
+    if (f_open(&f, filename, FA_READ) != FR_OK) {
+        return 0;
+    }
+    
+    UINT br;
+    int res = f_read(&f, dst, dst_size, &br);
+    f_close(&f);
+    
+    return res == FR_OK ? (int)br : 0;
 }