Manual Pages  — CUSE

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

cuse_load="YES"

#include <cuse.h>

void * cuse_vmalloc(unsigned 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. The returned pointer is always aligned to the system page size. The number and size of allocations is limited by the mmap(2) offset having to fit into a 32-bit variable typically for 32-bit applications.

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(). This function is NULL safe.

unsigned long cuse_vmoffset(void *) This function returns the mmap offset the client must use to access the allocated memory. The passed pointer must be aligned to the system page size.

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 created 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 callbacks.

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

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_ERR_NO_DEVICE

  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_FFLAG_COMPAT32

  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
};

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;
};