illumos: manual page: ddi

DDI_PEEK(9F) Kernel Functions for Drivers DDI_PEEK(9F)

NAME

ddi_peek, ddi_peek8, ddi_peek16, ddi_peek32, ddi_peek64 - read a value
from a location

SYNOPSIS

#include <sys/ddi.h>
#include <sys/sunddi.h>

int ddi_peek8(dev_info_t *dip, int8_t *addr, int8_t *valuep);

int ddi_peek16(dev_info_t *dip, int16_t *addr, int16_t *valuep);

int ddi_peek32(dev_info_t *dip, int32_t *addr, int32_t *valuep);

int ddi_peek64(dev_info_t *dip, int64_t *addr, int64_t *valuep);

INTERFACE LEVEL

illumos DDI specific (illumos DDI). The ddi_peekc(), ddi_peeks(),
ddi_peekl(), and ddi_peekd() functions are obsolete. Use, respectively,
ddi_peek8(), ddi_peek16(), ddi_peek32(), and ddi_peek64(), instead.

PARAMETERS

dip
A pointer to the device's dev_info structure.

addr
Virtual address of the location to be examined.

valuep
Pointer to a location to hold the result. If a null pointer is
specified, then the value read from the location will simply be
discarded.

DESCRIPTION

These routines cautiously attempt to read a value from a specified
virtual address, and return the value to the caller, using the parent
nexus driver to assist in the process where necessary.

If the address is not valid, or the value cannot be read without an error
occurring, an error code is returned.

The routines are most useful when first trying to establish the presence
of a device on the system in a driver's probe(9E) or attach(9E) routines.

RETURN VALUES

DDI_SUCCESS
The value at the given virtual address was successfully
read, and if valuep is non-null, *valuep will have been
updated.

DDI_FAILURE
An error occurred while trying to read the location.
*valuep is unchanged.

CONTEXT

These functions can be called from user, interrupt, or kernel context.

EXAMPLES

Example 1: Checking to see that the status register of a device is mapped

into the kernel address space:

if (ddi_peek8(dip, csr, (int8_t *)0) != DDI_SUCCESS) {
cmn_err(CE_WARN, "Status register not mapped");
return (DDI_FAILURE);
}

Example 2: Reading and logging the device type of a particular device:

int
xx_attach(dev_info_t *dip, ddi_attach_cmd_t cmd)
{
...
/* map device registers */
...

if (ddi_peek32(dip, id_addr, &id_value) != DDI_SUCCESS) {
cmn_err(CE_WARN, "%s%d: cannot read device identifier",
ddi_get_name(dip), ddi_get_instance(dip));
goto failure;
} else
cmn_err(CE_CONT, "!%s%d: device type 0x%x\n",
ddi_get_name(dip), ddi_get_instance(dip), id_value);
...
...

ddi_report_dev(dip);
return (DDI_SUCCESS);

failure:
/* free any resources allocated */
...
return (DDI_FAILURE);
}