Add cpu-sleep

README.md

@@ -24,6 +24,17 @@ $ pptk-led set red 0
 $ pptk-led set flash 255
 ```
 
+### cpu-sleep
+Puts secondary CPUs to sleep to save energy. Wakes them up to gain more CPU power.
+```
+$ pptk-cpu-sleep enable
+$ pptk-cpu-sleep get
+enabled
+$ pptk-cpu-sleep disable
+$ pptk-cpu-sleep get
+disabled
+```
+
 ## Build & Install
 ```
 $ meson build

meson.build

@@ -1,5 +1,8 @@
 project('PinePhone Toolkit', 'c')
+install_suid = ['rwsr-xr-x', 0, 0]
 executable('pptk-backlight', ['src/backlight.c'],
-  install: true, install_mode: ['rwsr-xr-x', 0, 0])
+  install: true, install_mode: install_suid)
 executable('pptk-led', ['src/led.c'],
-  install: true, install_mode: ['rwsr-xr-x', 0, 0])
+  install: true, install_mode: install_suid)
+executable('pptk-cpu-sleep', ['src/cpu-sleep.c'],
+  install: true, install_mode: install_suid)

src/cpu-sleep.c

@@ -0,0 +1,87 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static char *argv0 = "./cpu-sleep";
+static char *cpu_file_template = "/sys/devices/system/cpu/cpu%d/online";
+static int cpu_min = 1;
+static int cpu_max = 3;
+
+void print_usage()
+{
+    printf("usage: %s COMMAND\n", argv0);
+    printf("  COMMAND = {get, enable, disable}\n");
+    printf("    get     ... prints the current sleep state: 'enabled' or 'disabled'\n");
+    printf("    enable  ... enables sleep mode\n");
+    printf("    disable ... disables sleep mode\n");
+}
+
+void print_usage_and_fail()
+{
+    print_usage();
+    exit(EXIT_FAILURE);
+}
+
+void command_get()
+{
+    char filename[256];
+    sprintf(filename, cpu_file_template, 1);
+    FILE *fp = fopen(filename, "r");
+    if (fp == NULL) {
+        fprintf(stderr, "Cannot open file '%s' for reading.\n", filename);
+        exit(EXIT_FAILURE);
+    }
+    int buffer_length = 8;
+    char buffer[buffer_length];
+    fgets(buffer, buffer_length, fp);
+    fclose(fp);
+
+    if (strcmp(buffer, "1\n") == 0) {
+        printf("disabled\n");
+    } else {
+        printf("enabled\n");
+    }
+}
+
+void command_set(int value)
+{
+    if (setuid(0)) {
+        fprintf(stderr, "Cannot set root permissions via setuid(0).\n");
+        exit(EXIT_FAILURE);
+    }
+
+    for (int cpu = cpu_min; cpu <= cpu_max; cpu++) {
+        char filename[256];
+        sprintf(filename, cpu_file_template, cpu);
+        FILE *fp = fopen(filename, "w+");
+        if (fp == NULL) {
+            fprintf(stderr, "Cannot open file '%s' for writing.\n", filename);
+            exit(EXIT_FAILURE);
+        }
+        fprintf(fp, "%d\n", value);
+        fclose(fp);
+    }
+}
+
+int main(int argc, char *argv[])
+{
+    if (argc < 1) {
+        print_usage_and_fail();
+    }
+    argv0 = argv[0];
+    if (argc != 2) {
+        print_usage_and_fail();
+    }
+    char *command = argv[1];
+    if (strcmp(command, "get") == 0) {
+        command_get();
+    } else if (strcmp(command, "enable") == 0) {
+        command_set(0);
+    } else if (strcmp(command, "disable") == 0) {
+        command_set(1);
+    } else {
+        print_usage_and_fail();
+    }
+    exit(EXIT_SUCCESS);
+}