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 DDI_INTR_SET_NREQ 9F "Jan 5, 2009"
 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.