lib/sysfs: Explicit read/write length

Export a couple of routines to read/write an exact length, rather than a
strring.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 53 insertions, 9 deletions

diff --git a/lib/igt_sysfs.c b/lib/igt_sysfs.c
index ded10a67..dc178b3d 100644
--- a/lib/igt_sysfs.c
+++ b/lib/igt_sysfs.c
@@ -172,30 +172,74 @@ int igt_sysfs_open_parameters(int device)
 
 	return params;
 }
+
 /**
- * igt_sysfs_set:
+ * igt_sysfs_write:
  * @dir: directory for the device from igt_sysfs_open()
  * @attr: name of the sysfs node to open
- * @value: the string to write
+ * @data: the block to write from
+ * @len: the length to write
  *
- * This writes the value to the sysfs file.
+ * This writes @len bytes from @data to the sysfs file.
  *
  * Returns:
- * True on success, false on failure.
+ * The number of bytes written, or -1 on error.
  */
-bool igt_sysfs_set(int dir, const char *attr, const char *value)
+int igt_sysfs_write(int dir, const char *attr, const void *data, int len)
+{
+	int fd;
+
+	fd = openat(dir, attr, O_WRONLY);
+	if (fd < 0)
+		return false;
+
+	len = writeN(fd, data, len);
+	close(fd);
+
+	return len;
+}
+
+/**
+ * igt_sysfs_read:
+ * @dir: directory for the device from igt_sysfs_open()
+ * @attr: name of the sysfs node to open
+ * @data: the block to read into
+ * @len: the maximum length to read
+ *
+ * This reads @len bytes from the sysfs file to @data
+ *
+ * Returns:
+ * The length read, -1 on failure.
+ */
+int igt_sysfs_read(int dir, const char *attr, void *data, int len)
 {
-	int fd, len, ret;
+	int fd;
 
 	fd = openat(dir, attr, O_WRONLY);
 	if (fd < 0)
 		return false;
 
-	len = strlen(value);
-	ret = writeN(fd, value, len);
+	len = readN(fd, data, len);
 	close(fd);
 
-	return len == ret;
+	return len;
+}
+
+/**
+ * igt_sysfs_set:
+ * @dir: directory for the device from igt_sysfs_open()
+ * @attr: name of the sysfs node to open
+ * @value: the string to write
+ *
+ * This writes the value to the sysfs file.
+ *
+ * Returns:
+ * True on success, false on failure.
+ */
+bool igt_sysfs_set(int dir, const char *attr, const char *value)
+{
+	int len = strlen(value);
+	return igt_sysfs_write(dir, attr, value, len) == len;
 }
 
 /**