InterruptCharacteristic(), InterruptCharacteristic

Get or set a characteristic associated with an interrupt

Synopsis:

#include <sys/neutrino.h>

int InterruptCharacteristic( int type,
                             int id,
                             unsigned *new,
                             unsigned *old );

int InterruptCharacteristic_r( int type,
                               int id,
                               unsigned *new,
                               unsigned *old );

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Arguments:

type

The type of characteristic; the only type that's currently defined is:

_NTO_IC_LATENCY — set or get the interrupt's latency.

id

The identifier for the interrupt function, as returned by InterruptAttach(), InterruptAttachArray(), or InterruptAttachEvent().

new

NULL, or a pointer to the new value.

old

NULL, or a pointer to a location where the function can store the old value.

Description:

The InterruptCharacteristic() and InterruptCharacteristic_r() kernel calls set or get a characteristic of an interrupt. These functions are identical except in the way they indicate errors. See the Returns section for details.

The only type currently defined is _NTO_IC_LATENCY. If the new argument is non-NULL, it points to an unsigned that contains the new latency value for the interrupt, in nanoseconds. If the old argument is non-NULL, it's filled in with the old latency value for the interrupt. The default latency value is zero.

In order to set a latency, the calling thread must be in the process that attached to the interrupt.

The id argument can be -1. In this case, you're setting the global latency value for the system. If an interrupt attachment doesn't specify a latency value, the global latency number is used when calculating how deep a sleep state the kernel may use. In order to set the global latency value:

The process must have the PROCMGR_AID_IO ability enabled (see procmgr_ability()).
The calling thread must have obtained I/O privileges by calling:
```
ThreadCtl( _NTO_TCTL_IO, 0 );
```

Returns:

0 on success. If an error occurs:

InterruptCharacteristic() returns -1 and sets errno.
InterruptCharacteristic_r() returns a value from the Errors section and doesn't set errno.

Errors:

EFAULT: The function couldn't read from the new pointer, or it couldn't write to the old.
EINVAL: The type isn't _NTO_IC_LATENCY.
EPERM: You're trying to set a new latency, but the calling thread isn't in the attaching process or doesn't have I/O privileges.
ESRCH: The id isn't either a valid interrupt attachment identifier or -1.

Classification:

QNX Neutrino

Safety:
Cancellation point	No
Interrupt handler	Yes
Signal handler	Yes
Thread	Yes

InterruptCharacteristic(), InterruptCharacteristic_r()