panel-plugin/hdaps.c

   1 #ifdef HAVE_CONFIG_H
   2 #include <config.h>
   3 #endif
   4
   5 #include <dirent.h>
   6 #include <sys/types.h>
   7 #include <errno.h>
   8 #include <fcntl.h>
   9 #include <stdio.h>
  10 #include <string.h>
  11 #include "hdaps.h"
  12
  13 /* The most space we expect to need when reading in
  14    a file using these hdaps functions. To exceed 32
  15    bytes worth of content in unload_heads you'd have
  16    to throw your laptop hard as a motherfucker. */
  17 #define MAX_FILE_CONTENTS_SIZE 32
  18
  19 /* Where the block device names are located. */
  20 #define SYSFS_BLOCK_DEVICE_DIR "/sys/block/"
  21
  22
  23
  24 static int hdaps_device_exists(const char* device) {
  25   /* Determine whether or not a device (file) exists and has an
  26      unload_heads entry in sysfs. */
  27   char path[FILENAME_MAX];
  28   snprintf(path, FILENAME_MAX, UNLOAD_HEADS_FMT, device);
  29   return (access(path, F_OK) == 0);
  30 }
  31
  32
  33
  34 int get_hdaps_device_list(char list[MAX_HDAPS_DEVICES][FILENAME_MAX]) {
  35   /* Gets a list of devices which support HDAPS.
  36    * We start by getting every device in the sysfs
  37    * block device directory, and then eliminate those
  38    * which don't have an unload_heads entry.
  39    */
  40   int list_idx = 0;
  41   DIR *dp;
  42   struct dirent *ep;
  43
  44   dp = opendir(SYSFS_BLOCK_DEVICE_DIR);
  45
  46   if (dp != NULL) {
  47     while ((ep = readdir(dp)) && list_idx < MAX_HDAPS_DEVICES) {
  48       /* This next test covers "." and ".." too. */
  49       if (hdaps_device_exists(ep->d_name)) {
  50         strncpy(list[list_idx], ep->d_name, FILENAME_MAX);
  51         list_idx++;
  52       }
  53     }
  54
  55     (void)closedir(dp); /* Explicitly ignore this. */
  56   }
  57
  58   return list_idx;
  59 }
  60
  61
  62
  63 int slurp_file(const char* filename, char* buf, int max_bytes) {
  64   /* This function just reads the contents of filename
  65    * into buf, and returns the number of bytes read.
  66    */
  67   if (filename == NULL || buf == NULL) {
  68     /* HDAPS_SUPER_BAD_ERROR */
  69     return HDAPS_ERROR;
  70   }
  71
  72
  73   /* Return an error value by default. */
  74   int bytes_read = HDAPS_ERROR;
  75
  76   int fd = open(filename, O_RDONLY);
  77
  78   if (fd < 0) {
  79     /* open() didn't work. Report the error, and bail. */
  80     fprintf(stderr, "open(%s): %s\n", filename, strerror(errno));
  81     return HDAPS_ERROR;
  82   }
  83
  84   bytes_read = read(fd, buf, max_bytes-1);
  85
  86   if (bytes_read < 0) {
  87     /* Why did we read fewer than 0 bytes? */
  88     fprintf(stderr, "read(%s): %s\n", filename, strerror(errno));
  89   }
  90   else {
  91     /* Null-terminate buf if read() worked. */
  92     buf[bytes_read] = 0;
  93   }
  94
  95
  96   if (close(fd)) {
  97     /* Oh hey we should be able to close the file, too. */
  98     fprintf(stderr, "close(%s): %s\n", filename, strerror(errno));
  99   }
 100
 101   return bytes_read;
 102 }
 103
 104
 105
 106
 107 int parse_int_from_file(const char* filename) {
 108   /* Read an integer from a file. We expect the file
 109      to contain an integer (although in string form). */
 110
 111   char buf[MAX_FILE_CONTENTS_SIZE];
 112   int bytes_read = slurp_file(filename, buf, sizeof(buf));
 113
 114   if (bytes_read <= 0) {
 115     /* We can't parse what doesn't exist. Note that
 116      * reading "0" from a file should result in reading
 117      * at least 1 byte.
 118      */
 119     return HDAPS_ERROR;
 120   }
 121   else {
 122     /* If we read more than 0 bytes, hopefully we can
 123      * count on atoi to succeed. */
 124     return atoi(buf);
 125   }
 126 }