NAME¶

libcuse4bsd — Userland character device library

LIBRARY¶

Userland character device library (libcuse4bsd -lcuse4bsd)

SYNOPSIS¶

To load the required kernel module at boot time, place the following line in loader.conf(5):

cuse4bsd_load="YES"

#include <cuse4bsd.h>

DESCRIPTION¶

The libcuse4bsd library contains functions to create a character device in userspace. The libcuse4bsd library is thread safe.

LIBRARY INITIALISATION / DEINITIALISATION¶

int cuse_init(void) This function initialises libcuse4bsd. Must be called at the beginning of the program. This function returns 0 on success or a negative CUSE_ERR_XXX value on failure. If the cuse4bsd kernel module is not loaded, CUSE_ERR_NOT_LOADED is returned.

int cuse_uninit(void) Deinitialise libcuse4bsd. Can be called at the end of the application. This function returns 0 on success or a negative CUSE_ERR_XXX value on failure.

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 CUSE_ERR_XXX value on failure.

int cuse_alloc_unit_number_by_id(int *, int id) This function stores a uniq 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 cuse4bsd include file. See the CUSE_ID_XXX() macros for more information. This function returns 0 on success or a negative CUSE_ERR_XXX value on failure.

int cuse_free_unit_number(int) This function frees the given allocated system unit number. This function returns 0 on success or a negative CUSE_ERR_XXX value on failure.

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 CUSE_ERR_XXX value on failure.

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(). This function returns a valid data pointer on success or NULL on failure.

void cuse_vmfree(void *) This function frees memory allocated by cuse_vmalloc(). Note that the cuse4bsd library will internally not free the memory until the cuse_uninit() function is called and that the number of uniq 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 parallell I/O is required multiple threads must be created looping on this function. This function returns 0 on success or a negative CUSE_ERR_XXX value on failure.

void cuse_dev_set_per_file_handle(struct cuse_dev *, void *) , void * cuse_dev_get_per_file_handle(struct cuse_dev *) 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 callbacks.

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 pointers passed to the cm_read(), cm_write() and cm_ioctl() callback functions. These functions returns 0 on success or a negative CUSE_ERR_XXX value on failure.

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 CUSE_ERR_XXX value.

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 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 functions returns a CUSE_ERR_XXX value.

int cuse_close_t(struct cuse_dev *, int fflags) This functions returns a CUSE_ERR_XXX value.

int cuse_read_t(struct cuse_dev *, int fflags, void *peer_ptr, int len) This functions 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 functions 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 functions 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 functions returns a mask of CUSE_POLL_XXX values in case of failure and success. 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;
};

SEE ALSO¶

HISTORY¶

libcuse4bsd was written by Hans Petter Selasky .