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

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

#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);

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.


A pointer to the device's dev_info structure.


Virtual address of the location to be examined.


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.

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.


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


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

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

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:

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

attach(9E), probe(9E), ddi_poke(9F)

Writing Device Drivers

January 16, 2006 OmniOS