lib: add igt_debugfs_read()

A helpful function for when you want to read a whole debugfs file to a
string and don't want to worry about opening and closing file
descriptors and asserting buffer sizes.

We've been using this already for kms_frontbuffer_tracking and
kms_fbcon_fbt, so the only test with new code here is kms_fbc_crc.

Also notice that for kms_fbc_crc we had to increase the buffer size
since the file can sometimes be bigger than 64 bytes - depending on
the reason why FBC is disabled.

Of course, there are probably many other programs we can patch, but
I'm not doing this now.

v2: Add the macro to wrap sizeof() (Daniel).
v3: Add documentation for the macro too (Daniel).

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/igt_debugfs.h b/lib/igt_debugfs.h
index ece71486..78cb5e1c 100644
--- a/lib/igt_debugfs.h
+++ b/lib/igt_debugfs.h
@@ -34,6 +34,18 @@ enum pipe;
 int igt_debugfs_open(const char *filename, int mode);
 FILE *igt_debugfs_fopen(const char *filename,
 			const char *mode);
+void __igt_debugfs_read(const char *filename, char *buf, int buf_size);
+
+/**
+ * igt_debugfs_read:
+ * @filename: name of the debugfs file
+ * @buf: buffer where the contents will be stored, allocated by the caller.
+ *
+ * This is just a convenience wrapper for __igt_debugfs_read. See its
+ * documentation.
+ */
+#define igt_debugfs_read(filename, buf) \
+		__igt_debugfs_read((filename), (buf), sizeof(buf))
 
 /*
  * Pipe CRC