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LIBGEOM (3) \| C library functions \| Unix Manual Pages \| :man▋ NAME geom_stats_open, geom_stats_close, geom_stats_resync, geom_stats_snapshot_get, geom_stats_snapshot_free, geom_stats_snapshot_timestamp, geom_stats_snapshot_reset, geom_stats_snapshot_next, gctl_get_handle, gctl_ro_param, gctl_rw_param, gctl_issue, gctl_free, gctl_dump - userland API library for kernel GEOM subsystem CONTENTS Library Synopsis Description Examples See Also History Authors LIBRARY .Lb libgeom SYNOPSIS .In libgeom.h "Statistics Functions" void `geom_stats_close void` int `geom_stats_open void` void `geom_stats_resync void` "void "* `geom_stats_snapshot_get void` void `geom_stats_snapshot_free "void arg"` void* `geom_stats_snapshot_timestamp "void arg" "struct timespec tp"` void `geom_stats_snapshot_reset "void arg"` "struct g_stat " `geom_stats_snapshot_next "void arg"` "Control Functions" "struct gctl_req " `gctl_get_handle "void"` void `gctl_ro_param "struct gctl_req req" "const char name" "int len" "const void value"` void* `gctl_rw_param "struct gctl_req req" "const char name" "int len" "void value"` "const char " `gctl_issue "struct gctl_req req"` void* `gctl_free "struct gctl_req req"` void* `gctl_dump "struct gctl_req req" "FILE f"` DESCRIPTION The geom library contains the official and publicized API for interacting with the GEOM subsystem in the kernel. "Statistics Functions" GEOM collects statistics data for all consumers and providers, but does not perform any normalization or presentation on the raw data, this is left as an excercize for user-land presentation utilities. The `geom_stats_open` and `geom_stats_close` functions open and close the necessary pathways to access the raw statistics information in the kernel. These functions are likely to open one or more files and cache the file descriptors locally. The `geom_stats_open` function returns zero on success, and sets errno if not. The `geom_stats_resync` function will check if more statistics collection points have been added in the kernel since `geom_stats_open` or the previous call to `geom_stats_resync`. The `geom_stats_snapshot_get` function will acquire a snapshot of the raw data from the kernel, and while a reasonable effort is made to make this snapshot as atomic and consistent as possible, no guarantee is given that it will actually be so. The snapshot must be freed again using the `geom_stats_snapshot_free` function. The `geom_stats_snapshot_get` function returns `NULL` on failure. The `geom_stats_snapshot_timestamp` function provides access to the timestamp acquired in the snapshot. The `geom_stats_snapshot_reset` and `geom_stats_snapshot_next` functions provide an iterator over the statistics slots in the snapshot. The `geom_stats_snapshot_reset` function forces the internal pointer in the snapshot back to before the first item. The `geom_stats_snapshot_next` function returns the next item, and `NULL` if there are no more items in the snapshot. "Control Functions" The `gctl_` functions are used to send requests to GEOM classes. In order for a GEOM class to actually be able to receive these requests, it must have defined a "ctlreq" method. A .Vt "struct gctl_req " , obtained with `gctl_get_handle`, can hold any number of parameters, which must be added to it with `gctl_ro_param` (for read-only parameters) or `gctl_rw_param` (for read/write parameters). Both `gctl_ro_param` and `gctl_rw_param` take a string name, which is used to identify the parameter, and a value, which contains, in the read-only case, the data to be passed to the GEOM class, or, in the read/write case, a pointer to preallocated memory that the GEOM class should fill with the desired data. If len is negative, it is assumed that value is an ASCII string and the actual length is taken from the string length of value; otherwise it must hold the size of value. A parameter with a name containing the string "class" is mandatory for each request, and the corresponding value must hold the name of the GEOM class where the request should be sent to. Also mandatory for each request is a parameter with a name called "verb", and the corresponding value needs to hold the command string that the GEOM class should react upon. Once all desired parameters are filled in, the request must be sent to the GEOM subsystem with `gctl_issue`, which returns `NULL` on success, or a string containing the error message on failure. After the request is finished, the allocated memory should be released with `gctl_free`. The `gctl_dump` function can be used to format the contents of req to the open file handle pointed to by f, for debugging purposes. Error handling for the control functions is postponed until the call to `gctl_issue`, which returns `NULL` on success, or an error message corresponding to the first error which happened. EXAMPLES Create a request that is to be sent to the CCD class, and tell it to destroy a specific geom: H = gctl_get_handle(); gctl_ro_param(H, "verb", -1, "destroy geom"); gctl_ro_param(H, "class", -1, "CCD"); sprintf(buf, "ccd%d", ccd); gctl_ro_param(H, "geom", -1, buf); errstr = gctl_issue(H); if (errstr != NULL) err(1, "could not destroy ccd: %s", errstr); gctl_free(H); SEE ALSO HISTORY AUTHORS

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