Attempt a mode switch

platform.c

@@ -0,0 +1,64 @@
+#include <asm-generic/errno-base.h>
+#include <stdlib.h>
+#define PLATFORM_FILE
+#include "platform.h"
+
+static const char* const platform_input_path = "/sys/devices/platform/asus-mcu.0/input/mode";
+
+static rc71l_platform_t static_platform;
+
+void init_global_mode() {
+    global_platform = NULL;
+
+    if (access(platform_input_path, F_OK) == 0) {
+        FILE* mode_file = fopen(platform_input_path, "r");
+        if (mode_file == NULL) {
+            fprintf(stderr, "Unable to open the MCU platform mode file %s: modes cannot be switched.\n", platform_input_path);
+            return;
+        }
+
+        char mode_str[12];
+        unsigned long read_bytes = fread((void*)&mode_str[0], 1, sizeof(mode_str), mode_file);
+        if (read_bytes < 1) {
+            fprintf(stderr, "Unable to read the MCU platform mode file %s: no bytes.\n", platform_input_path);
+            fclose(mode_file);
+        }
+
+        static_platform.mode = strtoul(&mode_str[0], NULL, 10);
+
+        fclose(mode_file);
+
+        global_platform = &static_platform;
+        printf("Asus MCU platform found: current mode %lu\n", global_platform->mode);
+        global_platform->modes_count = 3;
+    } else {
+        fprintf(stderr, "Unable to find the MCU platform mode file %s: modes cannot be switched.\n", platform_input_path);
+    }
+}
+
+int cycle_mode() {
+    if (global_platform == NULL) {
+        fprintf(stderr, "Asus MCU not registered: aborting.\n");
+    }
+
+    char new_mode_str[] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
+    unsigned long new_mode = (global_platform->mode + 1) % global_platform->modes_count;
+    sprintf(new_mode_str, "%lu", new_mode);
+
+    FILE* mode_file = fopen(platform_input_path, "r");
+    if (mode_file == NULL) {
+        fprintf(stderr, "Unable to open the MCU platform mode file %s: modes cannot be switched.\n", platform_input_path);
+        return -1;
+    }
+
+    size_t len = strlen(new_mode_str);
+    const int write_bytes = fwrite((void*)&new_mode_str[0], 1, len, mode_file);
+    if (write_bytes < len) {
+        fprintf(stderr, "Error writing new mode: expected to write %d bytes, %d written.\n", (int)len, (int)write_bytes);
+        return -2;
+    }
+
+    fclose(mode_file);
+
+    return 0;
+}