man pages section 9: DDI and DKI Kernel Functions

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Updated: July 2014
 
 

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

Solaris DDI specific (Solaris 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(5) for descriptions of the following attributes:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Uncommitted
MT-Level
MT-Safe

See Also

attributes(5), 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.