xref: /dragonfly/share/man/man9/make_dev.9 (revision ae24b5e0) 
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25.\" $FreeBSD: src/share/man/man9/make_dev.9,v 1.2.2.3 2001/12/17 11:30:18 ru Exp $
26.\"
27.Dd August 3, 2016
28.Dt MAKE_DEV 9
29.Os
30.Sh NAME
31.Nm destroy_dev ,
32.Nm destroy_only_dev ,
33.Nm devfs_scan_callback ,
34.Nm dev_ops_intercept ,
35.Nm dev_ops_remove_all ,
36.Nm dev_ops_remove_minor ,
37.Nm dev_ops_restore ,
38.Nm make_dev ,
39.Nm make_dev_alias ,
40.Nm make_dev_covering ,
41.Nm make_only_dev ,
42.Nm reference_dev ,
43.Nm release_dev
44.Nd "device entry manipulation functions"
45.Sh SYNOPSIS
46.In sys/types.h
47.In sys/conf.h
48.In sys/devfs.h
49.Ft void
50.Fn destroy_dev "cdev_t dev"
51.Ft void
52.Fn destroy_only_dev "cdev_t dev"
53.Ft int
54.Fn devfs_scan_callback "devfs_scan_t *callback" "void *arg"
55.Ft struct dev_ops *
56.Fn dev_ops_intercept "cdev_t dev" "struct dev_ops *iops"
57.Ft int
58.Fn dev_ops_remove_all "struct dev_ops *ops"
59.Ft void
60.Fn dev_ops_restore "cdev_t dev" "struct dev_ops *oops"
61.Ft int
62.Fn dev_ops_remove_minor "struct dev_ops *ops" "int minor"
63.Ft cdev_t
64.Fn make_dev "struct dev_ops *ops" "int minor" "uid_t uid" "gid_t gid" "int perms" "const char *fmt" ...
65.Ft int
66.Fn make_dev_alias "cdev_t target" "const char *fmt" ...
67.Ft cdev_t
68.Fn make_dev_covering "struct dev_ops *ops" "struct dev_ops *bops" "int minor" "uid_t uid" "gid_t gid" "int perms" "const char *fmt" ...
69.Ft cdev_t
70.Fn make_only_dev "struct dev_ops *ops" "int minor" "uid_t uid" "gid_t gid" "int perms" "const char *fmt" ...
71.Ft cdev_t
72.Fn reference_dev "cdev_t dev"
73.Ft void
74.Fn release_dev "cdev_t dev"
75.Sh DESCRIPTION
76The
77.Fn make_dev
78function creates a
79.Vt cdev_t
80structure for a new device and makes the device name visible in the
81.Xr devfs 5
82mount points.
83The device's name must be unique.
84The name is the expansion of
85.Fa fmt
86and following arguments as
87.Xr kprintf 9
88would print it.
89The name determines its path under
90.Pa /dev .
91The permissions of the file specified in
92.Fa perms
93are defined in
94.In sys/stat.h :
95.Pp
96.Bd -literal -offset indent -compact
97#define S_IRWXU 0000700    /* RWX mask for owner */
98#define S_IRUSR 0000400    /* R for owner */
99#define S_IWUSR 0000200    /* W for owner */
100#define S_IXUSR 0000100    /* X for owner */
101
102#define S_IRWXG 0000070    /* RWX mask for group */
103#define S_IRGRP 0000040    /* R for group */
104#define S_IWGRP 0000020    /* W for group */
105#define S_IXGRP 0000010    /* X for group */
106
107#define S_IRWXO 0000007    /* RWX mask for other */
108#define S_IROTH 0000004    /* R for other */
109#define S_IWOTH 0000002    /* W for other */
110#define S_IXOTH 0000001    /* X for other */
111
112#define S_ISUID 0004000    /* set user id on execution */
113#define S_ISGID 0002000    /* set group id on execution */
114#define S_ISVTX 0001000    /* sticky bit */
115#if __BSD_VISIBLE
116#define S_ISTXT 0001000
117#endif
118.Ed
119.Pp
120The
121.Fa ops
122argument is a pointer to a
123.Vt dev_ops
124data structure, which is defined as follows:
125.Bd -literal
126struct dev_ops {
127        struct {
128                const char      *name;  /* base name, e.g. 'da' */
129                int              maj;   /* major device number */
130                u_int            flags; /* D_XXX flags */
131                void            *data;  /* custom driver data */
132                int              refs;  /* ref count */
133                int              id;
134        } head;
135
136#define dev_ops_first_field     d_default
137        d_default_t     *d_default;
138        d_open_t        *d_open;
139        d_close_t       *d_close;
140        d_read_t        *d_read;
141        d_write_t       *d_write;
142        d_ioctl_t       *d_ioctl;
143        d_mmap_t        *d_mmap;
144        d_strategy_t    *d_strategy;
145        d_dump_t        *d_dump;
146        d_psize_t       *d_psize;
147        d_kqfilter_t    *d_kqfilter;
148        d_clone_t       *d_clone;       /* clone from base dev_ops */
149        d_revoke_t      *d_revoke;
150#define dev_ops_last_field      d_revoke
151};
152.Ed
153.Pp
154While one can and should initialize the
155.Fa name
156and
157.Fa maj
158fields, they are effectively ignored.
159Device major numbers are assigned automatically out of an internal pool of
160major numbers, so there is no need to specify a unique major number in the
161.Vt dev_ops
162structure.
163.Pp
164Every member of the
165.Fn d_xxx_t
166family is defined as:
167.Bd -literal
168typedef int d_xxx_t (struct dev_xxx_args *ap);
169.Ed
170.Pp
171Therefore, if one wants to implement a
172.Fn mydev_open
173function, this is the way:
174.Bd -literal
175d_open_t mydev_open;
176
177int
178mydev_open(struct dev_open_args *ap)
179{
180}
181.Ed
182.Pp
183.Fn make_dev_covering
184is equivalent to make_dev, except that it also takes an argument
185.Fa bops
186which is set as the ops of the backing device for the newly created device.
187This function should be used whenever a device is created covering
188another raw device, as the disk subsystem does.
189.Pp
190.Fn make_only_dev
191creates a
192.Vt cdev_t
193structure and initializes it the same way
194.Fn make_dev
195would, but the device will not appear in the
196.Xr devfs 5
197namespace.
198.Pp
199.Fn destroy_dev
200takes the returned
201.Vt cdev_t
202from
203.Fn make_dev
204and destroys the registration for that device.
205It should not be used to destroy a
206.Vt cdev_t
207created by
208.Fn make_only_dev .
209.Pp
210.Fn destroy_only_dev
211takes the returned
212.Vt cdev_t
213from
214.Fn make_only_dev
215and destroys the registration for that device.
216It should not be used to destroy a
217.Vt cdev_t
218created by
219.Fn make_dev .
220.Pp
221.Fn make_dev_alias
222creates an automatic
223.Xr devfs 5
224link (alias) with the given name to the
225.Vt cdev_t
226specified by
227.Fa target .
228The
229.Vt cdev_t
230must have been created either by
231.Fn make_dev
232or bt a clone handler.
233Aliases are alternative names for devices in the
234.Xr devfs 5
235namespace.
236The lifetime of an alias is that of its associated
237.Vt cdev_t .
238Once the
239.Vt cdev_t
240is removed or destroyed, the alias is also destroyed and its name is
241removed from the
242.Xr devfs 5
243namespace.
244.Pp
245.Fn reference_dev
246adds a reference to
247.Fa dev .
248Callers generally add their own references when they are going to store a device
249node in a variable for long periods of time, to prevent a disassociation from
250freeing the node.
251.Pp
252.Fn release_dev
253releases a reference on
254.Fa dev .
255The device will be terminated when the last reference has been released.
256.Pp
257.Fn dev_ops_intercept
258intercepts the device operations vector of
259.Fa dev
260with
261.Fa iops .
262The old
263.Vt dev_ops
264is returned which may be used in a subsequent
265.Fn dev_ops_restore
266call.
267The function sets the
268.Dv SI_INTERCEPTED
269flag in
270.Fa dev .
271.Pp
272.Fn dev_ops_restore
273restores the device operations vector of
274.Fa dev
275to
276.Fa oops .
277Also it unsets the
278.Dv SI_INTERCEPTED
279flag in
280.Fa dev .
281.Pp
282.Fn dev_ops_remove_all
283destroys all the
284.Vt cdev_t
285with the given
286.Fa ops
287and removes the devices from the
288.Xr devfs 5
289namespace.
290This function is useful when uninitializing a driver.
291.Pp
292.Fn dev_ops_remove_minor
293destroys all the
294.Vt cdev_t
295with the given
296.Fa ops
297and
298.Fa minor
299and removes the devices from the
300.Xr devfs 5
301namespace.
302.Pp
303.Fn devfs_scan_callback
304calls the given
305.Fa callback
306function for every device registered in
307.Xr devfs 5 .
308The
309.Fa callback
310function has the following form:
311.Bd -literal
312devfs_scan_t mydev_scan_callback;
313
314void
315mydev_scan_callback(char *name, cdev_t dev, bool is_alias, void *arg)
316{
317};
318.Ed
319.Pp
320The
321.Fa name
322argument is the alias' name (if
323.Fa is_alias
324is
325.Dv true )
326or the
327.Vt cdev Ap s
328.Fa si_name
329field.
330.Sh HISTORY
331The
332.Fn make_dev
333and
334.Fn destroy_dev
335functions first appeared in
336.Fx 4.0 .
337.Pp
338A major overhaul of these functions occurred in
339.Dx 2.3
340with the addition of
341.Xr devfs 5 .
342