stat-util: add new APIs device_path_make_{major_minor|canonical}() and device_path_parse_major_minor()

device_path_make_{major_minor|canonical)  generate device node paths
given a mode_t and a dev_t. We have similar code all over the place,
let's unify this in one place. The former will generate a "/dev/char/"
or "/dev/block" path, and never go to disk. The latter then goes to disk
and resolves that path to the actual path of the device node.

device_path_parse_major_minor() reverses device_path_make_major_minor(),
also withozut going to disk.

We have similar code doing something like this at various places, let's
unify this in a single set of functions. This also allows us to teach
them special tricks, for example handling of the
/run/systemd/inaccessible/{blk|chr} device nodes, which we use for
masking device nodes, and which do not exist in /dev/char/* and
/dev/block/*

1 files changed, 4 insertions, 0 deletions

diff --git a/src/basic/stat-util.h b/src/basic/stat-util.h
index fe4a4bb717..0a08e642b5 100644
--- a/src/basic/stat-util.h
+++ b/src/basic/stat-util.h
@@ -81,3 +81,7 @@ int fd_verify_directory(int fd);
                 typeof(x) _x = (x), _y = 0;                             \
                 _x >= _y && _x < (UINT32_C(1) << 20);                   \
         })
+
+int device_path_make_major_minor(mode_t mode, dev_t devno, char **ret);
+int device_path_make_canonical(mode_t mode, dev_t devno, char **ret);
+int device_path_parse_major_minor(const char *path, mode_t *ret_mode, dev_t *ret_devno);