CUSE(3) BSD Library Functions Manual CUSE(3)
NAME
libcuse -- Userland character device library
LIBRARY
library ``libcuse''
SYNOPSIS
To load the required kernel module at boot time, place the following line in loader.conf(5):
cuse_load="YES"
#include <cuse.h>
DESCRIPTION
The libcuse library contains functions to create a character device in userspace. The libcuse library is thread safe.
LIBRARY INITIALISATION
/ DEINITIALISATION
int cuse_init(void) This function initialises libcuse. Must be called at the beginning of the program. This function returns 0 on success
or a negative value on failure. See CUSE_ERR_XXX for known error codes. If the cuse kernel module is not loaded, CUSE_ERR_NOT_LOADED is
returned.
int cuse_uninit(void) Deinitialise libcuse. Can be called at the end of the application. This function returns 0 on success or a negative
value on failure. See CUSE_ERR_XXX for known error codes.
UNIT MANAGEMENT
int cuse_alloc_unit_number(int *) This function stores a uniq system unit number at the pointed integer loation. This function returns 0 on
success or a negative value on failure. See CUSE_ERR_XXX for known error codes.
int cuse_alloc_unit_number_by_id(int *, int id) This function stores a unique system unit number at the pointed integer loation. The
returned unit number is uniq within the given ID. Valid ID values are defined by the cuse include file. See the CUSE_ID_XXX() macros for
more information. This function returns 0 on success or a negative value on failure. See CUSE_ERR_XXX for known error codes.
int cuse_free_unit_number(int) This function frees the given allocated system unit number. This function returns 0 on success or a negative
value on failure. See CUSE_ERR_XXX for known error codes.
int cuse_free_unit_number_by_id(int unit, int id) This function frees the given allocated system unit number belonging to the given ID. If
both the unit and id argument is -1, all allocated units will be freed. This function returns 0 on success or a negative value on failure.
See CUSE_ERR_XXX for known error codes.
LIBRARY USAGE
void * cuse_vmalloc(int size) This function allocates size bytes of memory. Only memory allocated by this function can be memory mapped by
mmap(2). This function returns a valid data pointer on success or NULL on failure.
int cuse_is_vmalloc_addr(void *) This function returns non-zero if the passed pointer points to a valid and non-freed allocation, as returned
by cuse_vmalloc(). Else this function returns zero.
void cuse_vmfree(void *) This function frees memory allocated by cuse_vmalloc(). Note that the cuse library will internally not free the
memory until the cuse_uninit() function is called and that the number of unique allocations is limited.
unsigned long cuse_vmoffset(void *) This function returns the mmap offset that the client must use to access the allocated memory.
struct cuse_dev * cuse_dev_create(const struct cuse_methods *mtod, void *priv0, void *priv1, uid_t, gid_t, int permission, const char *fmt,
...) This function creates a new character device according to the given parameters. This function returns a valid cuse_dev structure
pointer on success or NULL on failure. The device name can only contain a-z, A-Z, 0-9, dot, / and underscore characters.
void cuse_dev_destroy(struct cuse_dev *) This functions destroys a previously created character device.
void * cuse_dev_get_priv0(struct cuse_dev *), void * cuse_dev_get_priv1(struct cuse_dev *), void cuse_dev_set_priv0(struct cuse_dev *, void
*), void cuse_dev_set_priv1(struct cuse_dev *, void *) These functions are used to set and get the private data of the given cuse device.
int cuse_wait_and_process(void) This function will block and do event processing. If parallel I/O is required multiple threads must be cre-
ated looping on this function. This function returns 0 on success or a negative value on failure. See CUSE_ERR_XXX for known error codes.
void * cuse_dev_get_per_file_handle(struct cuse_dev *), void cuse_dev_set_per_file_handle(struct cuse_dev *, void *) These functions are used
to set and get the per-file-open specific handle and should only be used inside the cuse file operation callbacks.
void cuse_set_local(int) This function instructs cuse_copy_out() and cuse_copy_in() that the user pointer is local, if the argument passed to
it is non-zero. Else the user pointer is assumed to be at the peer application. This function should only be used inside the cuse file
operation callbacks. The value is reset to zero when the given file operation returns, and does not affect any other file operation call-
backs.
int cuse_get_local(void) Returns the current local state. See cuse_set_local().
int cuse_copy_out(const void *src, void *peer_dst, int len), int cuse_copy_in(const void *peer_src, void *dst, int len) These functions are
used to transfer data between the local application and the peer application. These functions must be used when operating on the data point-
ers passed to the cm_read(), cm_write(), and cm_ioctl() callback functions. These functions return 0 on success or a negative value on fail-
ure. See CUSE_ERR_XXX for known error codes.
int cuse_got_peer_signal(void) This function is used to check if a signal has been delivered to the peer application and should only be used
inside the cuse file operation callbacks. This function returns 0 if a signal has been delivered to the caller. Else it returns a negative
value. See CUSE_ERR_XXX for known error codes.
struct cuse_dev * cuse_dev_get_current(int *pcmd) This function is used to get the current cuse device pointer and the currently executing
command, by CUSE_CMD_XXX value. The pcmd argument is allowed to be NULL. This function should only be used inside the cuse file operation
callbacks. On success a valid cuse device pointer is returned. On failure NULL is returned.
void cuse_poll_wakeup(void) This function will wake up any file pollers.
LIBRARY LIMITATIONS
Transfer lengths for read(), write(), cuse_copy_in(), and cuse_copy_out() should not exceed what can fit into a 32-bit signed integer and is
defined by the CUSE_LENGTH_MAX() macro. Transfer lengths for ioctls should not exceed what is defined by the CUSE_BUFFER_MAX() macro.
LIBRARY CALLBACK METHODS
In general fflags are defined by CUSE_FFLAG_XXX and errors are defined by CUSE_ERR_XXX.
enum {
CUSE_ERR_NONE
CUSE_ERR_BUSY
CUSE_ERR_WOULDBLOCK
CUSE_ERR_INVALID
CUSE_ERR_NO_MEMORY
CUSE_ERR_FAULT
CUSE_ERR_SIGNAL
CUSE_ERR_OTHER
CUSE_ERR_NOT_LOADED
CUSE_POLL_NONE
CUSE_POLL_READ
CUSE_POLL_WRITE
CUSE_POLL_ERROR
CUSE_FFLAG_NONE
CUSE_FFLAG_READ
CUSE_FFLAG_WRITE
CUSE_FFLAG_NONBLOCK
CUSE_CMD_NONE
CUSE_CMD_OPEN
CUSE_CMD_CLOSE
CUSE_CMD_READ
CUSE_CMD_WRITE
CUSE_CMD_IOCTL
CUSE_CMD_POLL
CUSE_CMD_SIGNAL
CUSE_CMD_SYNC
CUSE_CMD_MAX
};
int cuse_open_t(struct cuse_dev *, int fflags) This function returns a CUSE_ERR_XXX value.
int cuse_close_t(struct cuse_dev *, int fflags) This function returns a CUSE_ERR_XXX value.
int cuse_read_t(struct cuse_dev *, int fflags, void *peer_ptr, int len) This function returns a CUSE_ERR_XXX value in case of failure or the
actually transferred length in case of success. cuse_copy_in() and cuse_copy_out() must be used to transfer data to and from the peer_ptr.
int cuse_write_t(struct cuse_dev *, int fflags, const void *peer_ptr, int len) This function returns a CUSE_ERR_XXX value in case of failure
or the actually transferred length in case of success. cuse_copy_in() and cuse_copy_out() must be used to transfer data to and from the
peer_ptr.
int cuse_ioctl_t(struct cuse_dev *, int fflags, unsigned long cmd, void *peer_data) This function returns a CUSE_ERR_XXX value in case of
failure or zero in case of success. cuse_copy_in() and cuse_copy_out() must be used to transfer data to and from the peer_data.
int cuse_poll_t(struct cuse_dev *, int fflags, int events) This function returns a mask of CUSE_POLL_XXX values in case of failure and suc-
cess. The events argument is also a mask of CUSE_POLL_XXX values.
struct cuse_methods {
cuse_open_t *cm_open;
cuse_close_t *cm_close;
cuse_read_t *cm_read;
cuse_write_t *cm_write;
cuse_ioctl_t *cm_ioctl;
cuse_poll_t *cm_poll;
};
HISTORY
libcuse was written by Hans Petter Selasky.
BSD
June 6, 2014 BSD