[igt-dev] [PATCH i-g-t 1/3] lib/debugfs: Function to read debugfs with the directory already open

[Dhinakaran Pandiyan]

tests/kms_frontbuffer_tracking and tests/kms_psr read debugfs nodes
several times after opening the directory once. There is already an
implementation of this in the kms_frontbuffer_tracking, moving that
functionality to the library will allow us to share the code with kms_psr
and kms_fbcon_fbt

Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
---
 lib/igt_debugfs.c                | 39 ++++++++++++++++++++++++--------
 lib/igt_debugfs.h                |  3 ++-
 tests/kms_frontbuffer_tracking.c |  7 ++----
 3 files changed, 34 insertions(+), 15 deletions(-)

diff --git a/lib/igt_debugfs.c b/lib/igt_debugfs.c
index f3196f43..ac46ebff 100644
--- a/lib/igt_debugfs.c
+++ b/lib/igt_debugfs.c
@@ -261,26 +261,47 @@ int igt_debugfs_open(int device, const char *filename, int mode)
 	return ret;
 }
 
+/**
+ * igt_debugfs_simple_read:
+ * @filename: file name
+ * @buf: buffer where the contents will be stored, allocated by the caller
+ * @size: size of the buffer
+ *
+ * This function is similar to __igt_debugfs_read, the difference is that it
+ * expects the debugfs directory to be open and it's descriptor passed as the
+ * first argument.
+ *
+ * Returns:
+ * -errorno on failure or bytes read on success
+ */
+int igt_debugfs_simple_read(int dir, const char *filename, char *buf, int size)
+{
+	int len;
+
+	len = igt_sysfs_read(dir, filename, buf, size - 1);
+	if (len < 0)
+		buf[0] = '\0';
+	else
+		buf[len] = '\0';
+
+	return len;
+}
+
 /**
  * __igt_debugfs_read:
  * @filename: file name
  * @buf: buffer where the contents will be stored, allocated by the caller
- * @buf_size: size of the buffer
+ * @size: size of the buffer
  *
  * This function opens the debugfs file, reads it, stores the content in the
  * provided buffer, then closes the file. Users should make sure that the buffer
  * provided is big enough to fit the whole file, plus one byte.
  */
-void __igt_debugfs_read(int fd, const char *filename, char *buf, int buf_size)
+void __igt_debugfs_read(int fd, const char *filename, char *buf, int size)
 {
-	int dir;
-	int len;
+	int dir = igt_debugfs_dir(fd);
 
-	dir = igt_debugfs_dir(fd);
-	len = igt_sysfs_read(dir, filename, buf, buf_size - 1);
-	if (len < 0)
-		len = 0;
-	buf[len] = '\0';
+	igt_debugfs_simple_read(dir, filename, buf, size);
 	close(dir);
 }
 
diff --git a/lib/igt_debugfs.h b/lib/igt_debugfs.h
index 8d25abfe..5e21a563 100644
--- a/lib/igt_debugfs.h
+++ b/lib/igt_debugfs.h
@@ -37,7 +37,8 @@ char *igt_debugfs_path(int device, char *path, int pathlen);
 int igt_debugfs_dir(int device);
 
 int igt_debugfs_open(int fd, const char *filename, int mode);
-void __igt_debugfs_read(int fd, const char *filename, char *buf, int buf_size);
+void __igt_debugfs_read(int fd, const char *filename, char *buf, int size);
+int igt_debugfs_simple_read(int dir, const char *filename, char *buf, int size);
 bool igt_debugfs_search(int fd, const char *filename, const char *substring);
 
 /**
diff --git a/tests/kms_frontbuffer_tracking.c b/tests/kms_frontbuffer_tracking.c
index 1dfd7c1c..04c371f4 100644
--- a/tests/kms_frontbuffer_tracking.c
+++ b/tests/kms_frontbuffer_tracking.c
@@ -720,12 +720,9 @@ static void set_mode_for_params(struct modeset_params *params)
 
 static void __debugfs_read(const char *param, char *buf, int len)
 {
-	len = igt_sysfs_read(drm.debugfs, param, buf, len - 1);
-	if (len < 0) {
+	len = igt_debugfs_simple_read(drm.debugfs, param, buf, len);
+	if (len < 0)
 		igt_assert_eq(len, -ENODEV);
-		len = 0;
-	}
-	buf[len] = '\0';
 }
 
 static int __debugfs_write(const char *param, char *buf, int len)
-- 
2.17.1