Getting Started with QNX Neutrino - QNX Software Systems

© 2009, QNX Software Systems GmbH & Co. KG. Alphabetical listing of connect and I/O functions
io_devctl()
int io_devctl (resmgr_context_t *ctp, io_devctl_t *msg,
RESMGR_OCB_T *ocb)
Classification: I/O
Default handler: iofunc_devctl_default()
Helper functions: iofunc_devctl()
Client functions: devctl(), ioctl()
Messages: _IO_DEVCTL
Data structure:
struct _io_devctl {
uint16_t type;
uint16_t combine_len;
int32_t dcmd;
int32_t nbytes;
int32_t zero;
};
struct _io_devctl_reply {
uint32_t zero;
int32_t ret_val;
int32_t nbytes;
int32_t zero2;
};
typedef union {
struct _io_devctl i;
struct _io_devctl_reply o;
} io_devctl_t;
Description: Performs the device I/O operation as passed from the client’s devctl() in
dcmd. The client encodes a direction into the top two bits of dcmd, indicating how the
devctl() is to transfer data (the “to” field refers to the _POSIX_DEVDIR_TO bit; the
“from” field refers to the _POSIX_DEVDIR_FROM bit):
to field from field Meaning
0 0 No data transfer
0 1 Transfer from driver to client
1 0 Transfer from client to driver
1 1 Transfer bidirectionally
In the case of no data transfer, the driver is expected to simply perform the command
given in dcmd. In the case of a data transfer, the driver is expected to transfer the data
from and/or to the client, using the helper functions resmgr_msgreadv() and
resmgr_msgwritev(). The client indicates the size of the transfer in the nbytes
April 30, 2009 Chapter 5 • Resource Managers 233