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2 .\" Copyright (c) 2007 Pawel Jakub Dawidek <pjd@FreeBSD.org>
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36 .Nm geom_stats_close ,
37 .Nm geom_stats_resync ,
38 .Nm geom_stats_snapshot_get ,
39 .Nm geom_stats_snapshot_free ,
40 .Nm geom_stats_snapshot_timestamp ,
41 .Nm geom_stats_snapshot_reset ,
42 .Nm geom_stats_snapshot_next ,
60 .Nd userland API library for kernel GEOM subsystem
65 .Ss "Statistics Functions"
67 .Fn geom_stats_close void
69 .Fn geom_stats_open void
71 .Fn geom_stats_resync void
73 .Fn geom_stats_snapshot_get void
75 .Fn geom_stats_snapshot_free "void *arg"
77 .Fn geom_stats_snapshot_timestamp "void *arg" "struct timespec *tp"
79 .Fn geom_stats_snapshot_reset "void *arg"
80 .Ft "struct devstat *"
81 .Fn geom_stats_snapshot_next "void *arg"
82 .Ss "Control Functions"
83 .Ft "struct gctl_req *"
84 .Fn gctl_get_handle "void"
86 .Fn gctl_ro_param "struct gctl_req *req" "const char *name" "int len" "const void *value"
88 .Fn gctl_rw_param "struct gctl_req *req" "const char *name" "int len" "void *value"
90 .Fn gctl_issue "struct gctl_req *req"
92 .Fn gctl_free "struct gctl_req *req"
94 .Fn gctl_dump "struct gctl_req *req" "FILE *f"
95 .Ss "Utility Functions"
97 .Fn g_open "const char *name" "int dowrite"
101 .Fn g_mediasize "int fd"
103 .Fn g_sectorsize "int fd"
107 .Fn g_delete "int fd" "off_t offset" "off_t length"
109 .Fn g_device_path "const char *devpath"
111 .Fn g_get_ident "int fd" "char *ident" "size_t size"
113 .Fn g_get_name "const char *ident" "char *name" "size_t size"
115 .Fn g_open_by_ident "const char *ident" "int dowrite" "char *name" "size_t size"
117 .Fn g_providername "int fd"
121 library contains the official and publicized API for
122 interacting with the GEOM subsystem in the kernel.
123 .Ss "Statistics Functions"
124 GEOM collects statistics data for all consumers and providers, but does
125 not perform any normalization or presentation on the raw data, this is
126 left as an exercise for user-land presentation utilities.
132 functions open and close the necessary pathways to access the raw
133 statistics information in the kernel.
134 These functions are likely to
135 open one or more files and cache the file descriptors locally.
138 function returns zero on success, and sets
143 .Fn geom_stats_resync
144 function will check if more statistics collection points have been
145 added in the kernel since
147 or the previous call to
148 .Fn geom_stats_resync .
151 .Fn geom_stats_snapshot_get
153 will acquire a snapshot of the raw data from the kernel, and while a
154 reasonable effort is made to make this snapshot as atomic and consistent
155 as possible, no guarantee is given that it will actually be so.
156 The snapshot must be freed again using the
157 .Fn geom_stats_snapshot_free
160 .Fn geom_stats_snapshot_get
166 .Fn geom_stats_snapshot_timestamp
168 provides access to the timestamp acquired in the snapshot.
171 .Fn geom_stats_snapshot_reset
173 .Fn geom_stats_snapshot_next
175 provide an iterator over the statistics slots in the snapshot.
177 .Fn geom_stats_snapshot_reset
179 forces the internal pointer in the snapshot back to before the first item.
181 .Fn geom_stats_snapshot_next
183 returns the next item, and
185 if there are no more items in the snapshot.
186 .Ss "Control Functions"
189 functions are used to send requests to GEOM classes.
191 class to actually be able to receive these requests, it must have defined a
195 .Vt "struct gctl_req *" ,
197 .Fn gctl_get_handle ,
198 can hold any number of parameters, which must be added to it with
200 (for read-only parameters) or
202 (for read/write parameters).
210 which is used to identify the parameter, and a
212 which contains, in the read-only case, the data to be passed to the
213 GEOM class, or, in the read/write case, a pointer to preallocated memory
214 that the GEOM class should fill with the desired data.
217 is negative, it is assumed that
221 string and the actual length is taken from the string length of
223 otherwise it must hold the size of
228 containing the string
230 is mandatory for each request, and the
233 must hold the name of the GEOM class where the request should be sent to.
235 Also mandatory for each request is a parameter with a
239 and the corresponding
241 needs to hold the command string that the GEOM class should react upon.
243 Once all desired parameters are filled in, the request must be sent to
244 the GEOM subsystem with
248 on success, or a string containing the error message
251 After the request is finished, the allocated memory should be released with
257 can be used to format the contents of
259 to the open file handle pointed to by
261 for debugging purposes.
263 Error handling for the control functions is postponed until the call
268 on success, or an error message corresponding to the
269 first error which happened.
270 .Ss "Utility Functions"
273 functions are used to communicate with GEOM providers.
277 function opens the given provider and returns file descriptor number, which can
278 be used with other functions.
281 argument indicates if operations that modify the provider (like
285 are going to be called.
289 function closes the provider.
293 function returns size of the given provider.
297 function returns sector size of the given provider.
303 request to flush write cache of the provider.
307 function tells the provider that the given data range is no longer used.
311 function returns the full path to a provider given a partial or full path to the
313 If the device can not be found or is not a valid geom provider, NULL is
318 function returns provider's fixed and unique identifier.
321 argument should be at least
327 function returns name of the provider, which identifier is equal to the
333 function opens provider using its ident, unlike
335 which uses provider's name.
340 the function will store provider's name there.
344 function returns the provider name of an open file descriptor.
345 If the file descriptor does not point to a valid geom provider, NULL is
352 return a value greater than or equal to
358 Create a request that is to be sent to the CCD class, and tell
359 it to destroy a specific geom:
360 .Bd -literal -offset indent
361 H = gctl_get_handle();
362 gctl_ro_param(H, "verb", -1, "destroy geom");
363 gctl_ro_param(H, "class", -1, "CCD");
364 sprintf(buf, "ccd%d", ccd);
365 gctl_ro_param(H, "geom", -1, buf);
366 errstr = gctl_issue(H);
368 err(1, "could not destroy ccd: %s", errstr);
372 .Pa http://ezine.daemonnews.org/200308/blueprints.html
379 .An Poul-Henning Kamp Aq phk@FreeBSD.org
380 .An Lukas Ertl Aq le@FreeBSD.org
381 .An Pawel Jakub Dawidek pjd@FreeBSD.org