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

NAME

ddi_intr_set_nreq - set the number of interrupts requested for a device
driver instance

SYNOPSIS

#include <sys/ddi_intr.h>


int ddi_intr_set_nreq(dev_info_t *dip, int nreq);

INTERFACE LEVEL

illumos DDI specific (illumos DDI).

PARAMETERS

dip
Pointer to the dev_info structure.


nreq
Number of interrupts requested.

DESCRIPTION

The ddi_intr_set_nreq() function changes the number of interrupts
requested by a device driver instance.


The nreq parameter is the total number of interrupt resources that this
instance of the device driver would like to have available. The nreq
parameter includes any interrupt resources already allocated by the
driver. For example, if the driver instance already has two MSI-X vectors
and it wants two more, it should call this function with an nreq
parameter set to four.


The nreq parameter can be any value between one and the maximum number of
interrupts supported by the device hardware, as reported by a call to the
ddi_intr_get_nintrs(9F) function. The driver receives a callback
notifying it in cases when it must release any previously allocated
interrupts, or when it is allowed to allocate more interrupts as a result
of its new nreq parameter.


The ddi_intr_set_nreq() function is not supported unless a driver is
already consuming interrupts, and if it has a registered callback handler
that can process actions related to changes in interrupt availability.
See ddi_cb_register(9F) for an explanation on how to enable this
functionality.

RETURN VALUES

The ddi_intr_set_nreq() function returns:

DDI_SUCCESS
on success


DDI_EINVAL
The operation is invalid because the nreq parameter is not
a legal value


DDI_ENOTSUP
The operation is not supported. The driver must have a
registered callback, and the system must have interrupt
pools implemented.


DDI_FAILURE
Implementation specific failure

CONTEXT

These functions can be called from kernel, non-interrupt context.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Private |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+

SEE ALSO

attributes(7), attach(9E), ddi_cb_register(9F), ddi_intr_alloc(9F),
ddi_intr_get_nintrs(9F)

NOTES

The Interrupt Resource Management feature is limited to device driver
instances that are using MSI-X interrupts (interrupt type
DDI_INTR_TYPE_MSIX). Attempts to use this function for any other type of
interrupts fails with DDI_ENOTSUP.


The total number of interrupts requested by the driver is initially
defined by the count parameter provided by the driver's first call to the
ddi_intr_alloc(9F) function, specifically during the driver instance's
attach(9E) routine. The ddi_intr_set_nreq() function is only used if the
driver instance experiences changes in its I/O load. In response to
increased I/O load, the driver may want to request additional interrupt
resources. In response to diminished I/O load. the driver may volunteer
to return extra interrupt resources back to the system.

August 22, 2023 DDI_INTR_SET_NREQ(9F)