// read the device major and minor number, using the devpath
// return 0 on success, and set *major and *minor
// return -ENOMEM on OOM
// return -errno on failure to open or read
static int vdev_linux_sysfs_read_dev_nums( struct vdev_linux_context* ctx, char const* devpath, unsigned int* major, unsigned int* minor ) {
int rc = 0;
int fd = 0;
ssize_t nr = 0;
char devbuf[101];
memset( devbuf, 0, 101 );
char* full_devpath = vdev_linux_sysfs_fullpath( ctx->sysfs_mountpoint, devpath, "dev" );
if( full_devpath == NULL ) {
return -ENOMEM;
}
// open device path
fd = open( full_devpath, O_RDONLY );
if( fd < 0 ) {
rc = -errno;
if( rc != -ENOENT ) {
vdev_error("open('%s') rc = %d\n", full_devpath, rc );
}
free( full_devpath );
return rc;
}
nr = vdev_read_uninterrupted( fd, devbuf, 100 );
if( nr < 0 ) {
rc = nr;
vdev_error("read('%s') rc = %d\n", full_devpath, rc );
free( full_devpath );
close( fd );
return rc;
}
close( fd );
free( full_devpath );
rc = vdev_linux_sysfs_parse_device_nums( devbuf, major, minor );
if( rc != 0 ) {
vdev_error("Failed to parse '%s'\n", devbuf );
rc = -EIO;
}
return rc;
}
// read a whole file into RAM
// return 0 on success, and set *file_buf and *file_buf_len
// return negative on error
int vdev_read_file( char const* path, char** file_buf, size_t* file_buf_len ) {
int fd = 0;
struct stat sb;
char* buf = NULL;
int rc = 0;
// get size
rc = stat( path, &sb );
if( rc != 0 ) {
rc = -errno;
return rc;
}
// read the uevent file itself
buf = (char*)calloc( sb.st_size, 1 );
if( buf == NULL ) {
return -ENOMEM;
}
fd = open( path, O_RDONLY );
if( fd < 0 ) {
rc = -errno;
free( buf );
return rc;
}
rc = vdev_read_uninterrupted( fd, buf, sb.st_size );
if( rc < 0 ) {
close( fd );
free( buf );
return rc;
}
close( fd );
*file_buf = buf;
*file_buf_len = rc;
return 0;
}
// read a sysfs attribute
int vdev_sysfs_read_attr( char const* sysfs_device_path, char const* attr_name, char** value, size_t* value_len ) {
int rc = 0;
int fd = 0;
struct stat sb;
char attr_path[4097];
sprintf(attr_path, "%s/%s", sysfs_device_path, attr_name );
rc = stat( attr_path, &sb );
if( rc != 0 ) {
rc = -errno;
return rc;
}
// regular file? return the contents
if( S_ISREG( sb.st_mode ) ) {
fd = open( attr_path, O_RDONLY );
if( fd < 0 ) {
rc = -errno;
fprintf(stderr, "[WARN]: open('%s') errno = %d\n", attr_path, rc );
return rc;
}
char* ret_value = (char*)calloc( sb.st_size + 1, 1 );
if( ret_value == NULL ) {
close( fd );
return -ENOMEM;
}
rc = vdev_read_uninterrupted( fd, ret_value, sb.st_size );
if( rc < 0 ) {
free( ret_value );
close( fd );
return rc;
}
close( fd );
*value = ret_value;
*value_len = sb.st_size;
return 0;
}
// symlink? return the actual link
else if( S_ISLNK( sb.st_mode ) ) {
char* ret_value = (char*)calloc( sb.st_size + 1, 1 );
if( ret_value == NULL ) {
return -ENOMEM;
}
rc = readlink( attr_path, ret_value, sb.st_size );
if( rc < 0 ) {
rc = -errno;
fprintf(stderr, "[WARN]: readlink('%s') errno = %d\n", attr_path, rc );
free( ret_value );
return rc;
}
*value = ret_value;
*value_len = sb.st_size + 1;
return 0;
}
// not sure what to do here
else {
return -EINVAL;
}
}
