xref: /freebsd/share/man/man9/make_dev.9 (revision 4b9d6057)
1.\" Copyright (c) 1999 Chris Costello
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25.Dd March 2, 2016
26.Dt MAKE_DEV 9
27.Os
28.Sh NAME
29.Nm make_dev ,
30.Nm make_dev_cred ,
31.Nm make_dev_credf ,
32.Nm make_dev_p ,
33.Nm make_dev_s ,
34.Nm make_dev_alias ,
35.Nm make_dev_alias_p ,
36.Nm destroy_dev ,
37.Nm destroy_dev_sched ,
38.Nm destroy_dev_sched_cb ,
39.Nm destroy_dev_drain ,
40.Nm dev_depends
41.Nd manage
42.Vt cdev Ns 's
43and DEVFS registration for devices
44.Sh SYNOPSIS
45.In sys/param.h
46.In sys/conf.h
47.Ft void
48.Fn make_dev_args_init "struct make_dev_args *args"
49.Ft int
50.Fn make_dev_s "struct make_dev_args *args" "struct cdev **cdev" "const char *fmt" ...
51.Ft int
52.Fn make_dev_alias_p "int flags" "struct cdev **cdev" "struct cdev *pdev" "const char *fmt" ...
53.Ft void
54.Fn destroy_dev "struct cdev *dev"
55.Ft void
56.Fn destroy_dev_sched "struct cdev *dev"
57.Ft void
58.Fn destroy_dev_sched_cb "struct cdev *dev" "void (*cb)(void *)" "void *arg"
59.Ft void
60.Fn destroy_dev_drain "struct cdevsw *csw"
61.Ft void
62.Fn dev_depends "struct cdev *pdev" "struct cdev *cdev"
63.Pp
64LEGACY INTERFACES
65.Ft struct cdev *
66.Fn make_dev "struct cdevsw *cdevsw" "int unit" "uid_t uid" "gid_t gid" "int perms" "const char *fmt" ...
67.Ft struct cdev *
68.Fn make_dev_cred "struct cdevsw *cdevsw" "int unit" "struct ucred *cr" "uid_t uid" "gid_t gid" "int perms" "const char *fmt" ...
69.Ft struct cdev *
70.Fn make_dev_credf "int flags" "struct cdevsw *cdevsw" "int unit" "struct ucred *cr" "uid_t uid" "gid_t gid" "int perms" "const char *fmt" ...
71.Ft int
72.Fn make_dev_p "int flags" "struct cdev **cdev" "struct cdevsw *devsw" "struct ucred *cr" "uid_t uid" "gid_t gid" "int mode" "const char *fmt" ...
73.Ft struct cdev *
74.Fn make_dev_alias "struct cdev *pdev" "const char *fmt" ...
75.Sh DESCRIPTION
76The
77.Fn make_dev_s
78function creates a
79.Fa cdev
80structure for a new device, which is returned into the
81.Fa cdev
82argument.
83It also notifies
84.Xr devfs 5
85of the presence of the new device, that causes corresponding nodes
86to be created.
87Besides this, a
88.Xr devctl 4
89notification is sent.
90The function takes the structure
91.Va struct make_dev_args args ,
92which specifies the parameters for the device creation:
93.Pp
94.Bd -literal -offset indent -compact
95struct make_dev_args {
96	size_t		 mda_size;
97	int		 mda_flags;
98	struct cdevsw	*mda_devsw;
99	struct ucred	*mda_cr;
100	uid_t		 mda_uid;
101	gid_t		 mda_gid;
102	int		 mda_mode;
103	int		 mda_unit;
104	void		*mda_si_drv1;
105	void		*mda_si_drv2;
106};
107.Ed
108Before use and filling with the desired values, the structure must be
109initialized by the
110.Fn make_dev_args_init
111function, which ensures that future kernel interface expansion does
112not affect driver source code or binary interface.
113.Pp
114The created device will be owned by
115.Va args.mda_uid ,
116with the group ownership as
117.Va args.mda_gid .
118The name is the expansion of
119.Va fmt
120and following arguments as
121.Xr printf 9
122would print it.
123The name determines its path under
124.Pa /dev
125or other
126.Xr devfs 5
127mount point and may contain slash
128.Ql /
129characters to denote subdirectories.
130The permissions of the file specified in
131.Va args.mda_mode
132are defined in
133.In sys/stat.h :
134.Pp
135.Bd -literal -offset indent -compact
136#define S_IRWXU 0000700    /* RWX mask for owner */
137#define S_IRUSR 0000400    /* R for owner */
138#define S_IWUSR 0000200    /* W for owner */
139#define S_IXUSR 0000100    /* X for owner */
140
141#define S_IRWXG 0000070    /* RWX mask for group */
142#define S_IRGRP 0000040    /* R for group */
143#define S_IWGRP 0000020    /* W for group */
144#define S_IXGRP 0000010    /* X for group */
145
146#define S_IRWXO 0000007    /* RWX mask for other */
147#define S_IROTH 0000004    /* R for other */
148#define S_IWOTH 0000002    /* W for other */
149#define S_IXOTH 0000001    /* X for other */
150
151#define S_ISUID 0004000    /* set user id on execution */
152#define S_ISGID 0002000    /* set group id on execution */
153#define S_ISVTX 0001000    /* sticky bit */
154#ifndef _POSIX_SOURCE
155#define S_ISTXT 0001000
156#endif
157.Ed
158.Pp
159The
160.Va args.mda_cr
161argument specifies credentials that will be stored in the
162.Fa si_cred
163member of the initialized
164.Fa struct cdev .
165.Pp
166The
167.Va args.mda_flags
168argument alters the operation of
169.Fn make_dev_s.
170The following values are currently accepted:
171.Pp
172.Bl -tag -width "It Dv MAKEDEV_CHECKNAME" -compact -offset indent
173.It Dv MAKEDEV_REF
174reference the created device
175.It Dv MAKEDEV_NOWAIT
176do not sleep, the call may fail
177.It Dv MAKEDEV_WAITOK
178allow the function to sleep to satisfy malloc
179.It Dv MAKEDEV_ETERNAL
180created device will be never destroyed
181.It Dv MAKEDEV_CHECKNAME
182return an error if the device name is invalid or already exists
183.El
184.Pp
185Only
186.Dv MAKEDEV_NOWAIT ,
187.Dv MAKEDEV_WAITOK
188and
189.Dv MAKEDEV_CHECKNAME
190values are accepted for the
191.Fn make_dev_alias_p
192function.
193.Pp
194The
195.Dv MAKEDEV_WAITOK
196flag is assumed if none of
197.Dv MAKEDEV_WAITOK ,
198.Dv MAKEDEV_NOWAIT
199is specified.
200.Pp
201The
202.Xr dev_clone 9
203event handler shall specify
204.Dv MAKEDEV_REF
205flag when creating a device in response to lookup, to avoid race where
206the device created is destroyed immediately after
207.Xr devfs_lookup 9
208drops his reference to cdev.
209.Pp
210The
211.Dv MAKEDEV_ETERNAL
212flag allows the kernel to not acquire some locks when translating system
213calls into the cdevsw methods calls.
214It is responsibility of the driver author to make sure that
215.Fn destroy_dev
216is never called on the returned cdev.
217For the convenience, use the
218.Dv MAKEDEV_ETERNAL_KLD
219flag for the code that can be compiled into kernel or loaded
220(and unloaded) as loadable module.
221.Pp
222A panic will occur if the
223.Dv MAKEDEV_CHECKNAME
224flag is not specified
225and the device name is invalid or already exists.
226.Pp
227The
228.Fn make_dev_p
229use of the form
230.Bd -literal -offset indent
231struct cdev *dev;
232int res;
233res = make_dev_p(flags, &dev, cdevsw, cred, uid, gid, perms, name);
234.Ed
235is equivalent to the code
236.Bd -literal -offset indent
237struct cdev *dev;
238struct make_dev_args args;
239int res;
240
241make_dev_args_init(&args);
242args.mda_flags = flags;
243args.mda_devsw = cdevsw;
244args.mda_cred = cred;
245args.mda_uid = uid;
246args.mda_gid = gid;
247args.mda_mode = perms;
248res = make_dev_s(&args, &dev, name);
249.Ed
250.Pp
251Similarly, the
252.Fn make_dev_credf
253function call is equivalent to
254.Bd -literal -offset indent
255	(void) make_dev_s(&args, &dev, name);
256.Ed
257In other words,
258.Fn make_dev_credf
259does not allow the caller to obtain the return value, and in
260kernels compiled with the
261.Va INVARIANTS
262options, the function asserts that the device creation succeeded.
263.Pp
264The
265.Fn make_dev_cred
266function is equivalent to the call
267.Bd -literal -offset indent
268make_dev_credf(0, cdevsw, unit, cr, uid, gid, perms, fmt, ...);
269.Ed
270.Pp
271The
272.Fn make_dev
273function call is the same as
274.Bd -literal -offset indent
275make_dev_credf(0, cdevsw, unit, NULL, uid, gid, perms, fmt, ...);
276.Ed
277.Pp
278The
279.Fn make_dev_alias_p
280function takes the returned
281.Ft cdev
282from
283.Fn make_dev
284and makes another (aliased) name for this device.
285It is an error to call
286.Fn make_dev_alias_p
287prior to calling
288.Fn make_dev .
289.Pp
290The
291.Fn make_dev_alias
292function is similar to
293.Fn make_dev_alias_p
294but it returns the resulting aliasing
295.Ft *cdev
296and may not return an error.
297.Pp
298The
299.Fa cdev
300returned by
301.Fn make_dev_s
302and
303.Fn make_dev_alias_p
304has two fields,
305.Fa si_drv1
306and
307.Fa si_drv2 ,
308that are available to store state.
309Both fields are of type
310.Ft void * ,
311and can be initialized simultaneously with the
312.Va cdev
313allocation by filling
314.Va args.mda_si_drv1
315and
316.Va args.mda_si_drv2
317members of the
318.Fn make_dev_s
319argument structure, or filled after the
320.Va cdev
321is allocated, if using legacy interfaces.
322In the latter case, the driver should handle the race of
323accessing uninitialized
324.Va si_drv1
325and
326.Va si_drv2
327itself.
328These are designed to replace the
329.Fa unit
330argument to
331.Fn make_dev ,
332which can be obtained with
333.Fn dev2unit .
334.Pp
335The
336.Fn destroy_dev
337function takes the returned
338.Fa cdev
339from
340.Fn make_dev
341and destroys the registration for that device.
342The notification is sent to
343.Xr devctl 4
344about the destruction event.
345Do not call
346.Fn destroy_dev
347on devices that were created with
348.Fn make_dev_alias .
349.Pp
350The
351.Fn dev_depends
352function establishes a parent-child relationship between two devices.
353The net effect is that a
354.Fn destroy_dev
355of the parent device will also result in the destruction of the
356child device(s),
357if any exist.
358A device may simultaneously be a parent and a child,
359so it is possible to build a complete hierarchy.
360.Pp
361The
362.Fn destroy_dev_sched_cb
363function schedules execution of the
364.Fn destroy_dev
365for the specified
366.Fa cdev
367in the safe context.
368After
369.Fn destroy_dev
370is finished, and if the supplied
371.Fa cb
372is not
373.Dv NULL ,
374the callback
375.Fa cb
376is called, with argument
377.Fa arg .
378The
379.Fn destroy_dev_sched
380function is the same as
381.Bd -literal -offset indent
382destroy_dev_sched_cb(cdev, NULL, NULL);
383.Ed
384.Pp
385The
386.Fn d_close
387driver method cannot call
388.Fn destroy_dev
389directly.
390Doing so causes deadlock when
391.Fn destroy_dev
392waits for all threads to leave the driver methods.
393Also, because
394.Fn destroy_dev
395sleeps, no non-sleepable locks may be held over the call.
396The
397.Fn destroy_dev_sched
398family of functions overcome these issues.
399.Pp
400The device driver may call the
401.Fn destroy_dev_drain
402function to wait until all devices that have supplied
403.Fa csw
404as cdevsw, are destroyed.
405This is useful when driver knows that
406.Fn destroy_dev_sched
407is called for all instantiated devices, but need to postpone module
408unload until
409.Fn destroy_dev
410is actually finished for all of them.
411.Sh RETURN VALUES
412If successful,
413.Fn make_dev_s
414and
415.Fn make_dev_p
416will return 0, otherwise they will return an error.
417If successful,
418.Fn make_dev_credf
419will return a valid
420.Fa cdev
421pointer, otherwise it will return
422.Dv NULL .
423.Sh ERRORS
424The
425.Fn make_dev_s ,
426.Fn make_dev_p
427and
428.Fn make_dev_alias_p
429calls will fail and the device will be not registered if:
430.Bl -tag -width Er
431.It Bq Er ENOMEM
432The
433.Dv MAKEDEV_NOWAIT
434flag was specified and a memory allocation request could not be satisfied.
435.It Bq Er ENAMETOOLONG
436The
437.Dv MAKEDEV_CHECKNAME
438flag was specified and the provided device name is longer than
439.Dv SPECNAMELEN .
440.It Bq Er EINVAL
441The
442.Dv MAKEDEV_CHECKNAME
443flag was specified and the provided device name is empty, contains a
444.Qq \&.
445or
446.Qq ..
447path component or ends with
448.Ql / .
449.It Bq Er EINVAL
450The
451.Dv MAKEDEV_CHECKNAME
452flag was specified and the provided device name contains invalid characters.
453.It Bq Er EEXIST
454The
455.Dv MAKEDEV_CHECKNAME
456flag was specified and the provided device name already exists.
457.El
458.Sh SEE ALSO
459.Xr devctl 4 ,
460.Xr devfs 5 ,
461.Xr dev_clone 9
462.Sh HISTORY
463The
464.Fn make_dev
465and
466.Fn destroy_dev
467functions first appeared in
468.Fx 4.0 .
469The function
470.Fn make_dev_alias
471first appeared in
472.Fx 4.1 .
473The function
474.Fn dev_depends
475first appeared in
476.Fx 5.0 .
477The functions
478.Fn make_dev_credf ,
479.Fn destroy_dev_sched ,
480.Fn destroy_dev_sched_cb
481first appeared in
482.Fx 7.0 .
483The function
484.Fn make_dev_p
485first appeared in
486.Fx 8.2 .
487The function
488.Fn make_dev_s
489first appeared in
490.Fx 11.0 .
491