lib/sysfs: allow to write to sysfs attributes

Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/include/sysfs.h b/include/sysfs.h
index 85a8910c642dab389f142c83124237b891be89e2..3ff20cb2703cbe81ec8ef544ab0d88168b89375d 100644 (file)
--- a/include/sysfs.h
+++ b/include/sysfs.h
@@ -58,6 +58,9 @@ extern int sysfs_read_s64(struct sysfs_cxt *cxt, const char *attr, int64_t *res)
 extern int sysfs_read_u64(struct sysfs_cxt *cxt, const char *attr, uint64_t *res);
 extern int sysfs_read_int(struct sysfs_cxt *cxt, const char *attr, int *res);
 
+extern int sysfs_write_string(struct sysfs_cxt *cxt, const char *attr, const char *str);
+extern int sysfs_write_u64(struct sysfs_cxt *cxt, const char *attr, uint64_t num);
+
 extern char *sysfs_get_devname(struct sysfs_cxt *cxt, char *buf, size_t bufsiz);
 
 extern char *sysfs_strdup(struct sysfs_cxt *cxt, const char *attr);

diff --git a/lib/sysfs.c b/lib/sysfs.c
index bbe238b7c851a117c25e97ec4ec7b193fc48eece..e2baf7fcd3e98ad0cdf42dd625b2abf03b603e2f 100644 (file)
--- a/lib/sysfs.c
+++ b/lib/sysfs.c
@@ -11,6 +11,7 @@
 #include "pathnames.h"
 #include "sysfs.h"
 #include "fileutils.h"
+#include "all-io.h"
 
 char *sysfs_devno_attribute_path(dev_t devno, char *buf,
                                 size_t bufsiz, const char *attr)
@@ -204,9 +205,9 @@ int sysfs_has_attribute(struct sysfs_cxt *cxt, const char *attr)
        return sysfs_stat(cxt, attr, &st) == 0;
 }
 
-static int sysfs_open(struct sysfs_cxt *cxt, const char *attr)
+static int sysfs_open(struct sysfs_cxt *cxt, const char *attr, int flags)
 {
-       int fd = open_at(cxt->dir_fd, cxt->dir_path, attr, O_RDONLY|O_CLOEXEC);
+       int fd = open_at(cxt->dir_fd, cxt->dir_path, attr, flags);
 
        if (fd == -1 && errno == ENOENT &&
            strncmp(attr, "queue/", 6) == 0 && cxt->parent) {
@@ -214,8 +215,7 @@ static int sysfs_open(struct sysfs_cxt *cxt, const char *attr)
                /* Exception for "queue/<attr>". These attributes are available
                 * for parental devices only
                 */
-               fd = open_at(cxt->parent->dir_fd, cxt->dir_path, attr,
-                               O_RDONLY|O_CLOEXEC);
+               fd = open_at(cxt->parent->dir_fd, cxt->dir_path, attr, flags);
        }
        return fd;
 }
@@ -239,7 +239,7 @@ DIR *sysfs_opendir(struct sysfs_cxt *cxt, const char *attr)
        int fd = -1;
 
        if (attr)
-               fd = sysfs_open(cxt, attr);
+               fd = sysfs_open(cxt, attr, O_RDONLY|O_CLOEXEC);
 
        else if (cxt->dir_fd >= 0)
                /* request to open root of device in sysfs (/sys/block/<dev>)
@@ -264,7 +264,7 @@ DIR *sysfs_opendir(struct sysfs_cxt *cxt, const char *attr)
 
 static FILE *sysfs_fopen(struct sysfs_cxt *cxt, const char *attr)
 {
-       int fd = sysfs_open(cxt, attr);
+       int fd = sysfs_open(cxt, attr, O_RDONLY|O_CLOEXEC);
 
        return fd < 0 ? NULL : fdopen(fd, "r" UL_CLOEXECSTR);
 }
@@ -419,6 +419,42 @@ int sysfs_read_int(struct sysfs_cxt *cxt, const char *attr, int *res)
        return -1;
 }
 
+int sysfs_write_string(struct sysfs_cxt *cxt, const char *attr, const char *str)
+{
+       int fd = sysfs_open(cxt, attr, O_WRONLY|O_CLOEXEC);
+       int rc, errsv;
+
+       if (fd < 0)
+               return -errno;
+       rc = write_all(fd, str, strlen(str));
+
+       errsv = errno;
+       close(fd);
+       errno = errsv;
+       return rc;
+}
+
+int sysfs_write_u64(struct sysfs_cxt *cxt, const char *attr, uint64_t num)
+{
+       char buf[sizeof(stringify_value(ULLONG_MAX))];
+       int fd, rc = 0, len, errsv;
+
+       fd = sysfs_open(cxt, attr, O_WRONLY|O_CLOEXEC);
+       if (fd < 0)
+               return -errno;
+
+       len = snprintf(buf, sizeof(buf), "%ju", num);
+       if (len < 0 || (size_t) len + 1 > sizeof(buf))
+               rc = -errno;
+       else
+               rc = write_all(fd, buf, len);
+
+       errsv = errno;
+       close(fd);
+       errno = errsv;
+       return rc;
+}
+
 char *sysfs_strdup(struct sysfs_cxt *cxt, const char *attr)
 {
        char buf[1024];