fs: implement is_tftp_fs()

Some commands need files in which they can lseek backwards which
is particularly not possible on TFTP. Instead of hiding this
behind can_lseek_backward() create a function for it which tests
if the file is on TFTP directly rather than using different
lseek operations.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

2 files changed, 32 insertions, 0 deletions

diff --git a/fs/fs.c b/fs/fs.c
index 6f15e93ba9..e073e3577d 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -1906,3 +1906,25 @@ char *path_get_linux_rootarg(const char *path)
 
 	return xstrdup(str);
 }
+
+/**
+ * __is_tftp_fs() - return true when path is mounted on TFTP
+ * @path: The path
+ *
+ * Do not use directly, use is_tftp_fs instead.
+ *
+ * Return: true when @path is on TFTP, false otherwise
+ */
+bool __is_tftp_fs(const char *path)
+{
+	struct fs_device_d *fsdev;
+
+	fsdev = get_fsdevice_by_path(path);
+	if (!fsdev)
+		return false;
+
+	if (strcmp(fsdev->driver->drv.name, "tftp"))
+		return false;
+
+	return true;
+}
diff --git a/include/fs.h b/include/fs.h
index 3d88bfad4a..d75a1ef644 100644
--- a/include/fs.h
+++ b/include/fs.h
@@ -121,6 +121,16 @@ static inline int can_lseek_backward(int fd)
 	return 1;
 }
 
+bool __is_tftp_fs(const char *path);
+
+static inline bool is_tftp_fs(const char *path)
+{
+	if (!IS_ENABLED(CONFIG_FS_TFTP))
+		return false;
+
+	return __is_tftp_fs(path);
+}
+
 #define drv_to_fs_driver(d) container_of(d, struct fs_driver_d, drv)
 
 int flush(int fd);