docs/manual/makedev-syntax.txt

[[makedev-syntax]]
Makedev syntax documentation
----------------------------

The makedev syntax is used across several places in Buildroot to
define changes to be made for permissions or which device files to
create and how to create them, in order to avoid to call mkdnod every
now and then.

This syntax is derived from the makedev utility, and a more complete
documentation can be found in the +package/makedevs/README+ file.

It takes the form of a line for each file, with the following layout:

|===========================================================
|name |type |mode |uid |gid |major |minor |start |inc |count
|===========================================================

There is a few non-trivial blocks here:

- +name+ is the path to the file you want to create/modify
- +type+ is the type of the file, being one of :
  * f: a regular file
  * d: a directory
  * c: a character device file
  * b: a block device file
  * p: a named pipe
- +mode+, +uid+ and +gid+ are the usual permissions stuff
- +major+ and +minor+ are here for device files
- +start+, +inc+ and +count+ are when you want to create a whole batch
  of files, and can be reduced to a loop, beginning at +start+,
  incrementing its counter by +inc+ until it reaches +count+

Let's say you want to change the permissions of a given file, using
this syntax, you will need to put:
-------------------------------------------------------------------
/usr/bin/foobar	f	644	0	0	-	-	-	-	-
-------------------------------------------------------------------

On the other hand, if you want to create the device file +/dev/hda+
and the corresponding 15 files for the partitions, you will need for
+/dev/hda+:

-------------------------------------------------------------------
/dev/hda	b	640	0	0	3	0	0	0	-
-------------------------------------------------------------------

and then for device files corresponding to the partitions of
+/dev/hda+, +/dev/hdaX+, +X+ ranging from 1 to 15:

-------------------------------------------------------------------
/dev/hda	b	640	0	0	3	1	1	1	15
-------------------------------------------------------------------