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Driver Entry Points

read(9E)

INTERFACE LEVEL
PARAMETERS
DESCRIPTION
RETURN VALUES
EXAMPLES
SEE ALSO

NAME

read - read data from a device

SYNOPSIS

#include <sys/types.h> #include <sys/errno.h> #include <sys/open.h> #include <sys/uio.h> #include <sys/cred.h> #include <sys/ddi.h> #include <sys/sunddi.h> int prefixread(dev_t dev, struct uio *uio_p, cred_t *cred_p);

INTERFACE LEVEL

Architecture independent level 1 (DDI/DKI). This entry point is optional.

PARAMETERS

dev: Device number.
uio_p: Pointer to the uio(9S) structure that describes where the data is to be stored in user space.
cred_p: Pointer to the user credential structure for the I/O transaction.

DESCRIPTION

The driver read() routine is called indirectly through cb_ops(9S) by the read(2) system call. The read() routine should check the validity of the minor number component of dev and the user credential structure pointed to by cred_p (if pertinent). The read() routine should supervise the data transfer into the user space described by the uio(9S) structure.

RETURN VALUES

The read() routine should return 0 for success, or the appropriate error number.

EXAMPLES

Example 1. read routine using physio

The following is an example of a read() routine using physio(9F) to perform reads from a non-seekable device:

static int xxread(dev_t dev, struct uio *uiop, cred_t *credp) { int rval; offset_t off; int instance; xx_t xx; instance = getminor(dev); xx = ddi_get_soft_state(xxstate, instance); if (xx == NULL) return (ENXIO); off = uiop->uio_loffset; rval = physio(xxstrategy, NULL, dev, B_READ, xxmin, uiop); uiop->uio_loffset = off; return (rval); }