INTRENABLE(9) INTRENABLE(9)
NAME
intrenable, intrdisable - enable (disable) an interrupt
handler
SYNOPSIS
void intrenable(int v, void (*f)(Ureg*, void*), void* a, int
tbdf, char *name)
void intrdisable(int v, void (*f)(Ureg*, void*), void* a,
int tbdf, char *name)
DESCRIPTION
Intrenable registers f to be called by the kernel's inter-
rupt controller driver each time an interrupt denoted by v
occurs, and unmasks the corresponding interrupt in the
interrupt controller. The encoding of v is platform-
dependent; it is often an interrupt vector number, but can
be more complex. Tbdf is a platform-dependent value that
might further qualify v. It might for instance denote the
type of bus, bus instance, device number and function (fol-
lowing the PCI device indexing scheme), hence its name, but
can have platform-dependent meaning. Name is a string that
should uniquely identify the corresponding device (eg,
"uart0"); again it is usually platform-dependent.
Intrenable supports sharing of interrupt levels when the
hardware does.
Almost invariably f is a function defined in a device driver
to carry out the device-specific work associated with a
given interrupt. The pointer a is passed to f; typically it
points to the driver's data for a given device or con-
troller. It also passes f a Ureg* value that contains the
registers saved by the interrupt handler (the contents are
platform specific; see the platform's include file ureg.h).
F is invoked by underlying code in the kernel that is
invoked directly from the hardware vectors. It is therefore
not running in any process (see kproc(9); indeed, on many
platforms the current process pointer (up) will be nil.
There are many restrictions on kernel functions running out-
side a process, but a fundamental one is that they must not
sleep(9), although they often call wakeup to signal the
occurrence of an event associated with the interrupt.
Qio(9) and other manual pages note which functions are safe
for f to call.
The interrupt controller driver does whatever is required to
acknowledge or dismiss the interrupt signal in the interrupt
controller, before calling f, for edge-triggered interrupts,
and after calling f for level-triggered ones. F is
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INTRENABLE(9) INTRENABLE(9)
responsible for deal with the cause of the interrupt in the
device, including any acknowledgement required in the
device, before it returns.
Intrdisable removes any registration previously made by
intrenable with matching parameters, and if no other inter-
rupt is active on v, it masks the interrupt in the con-
troller. Device drivers that are not dynamically configured
tend to call intrenable during reset or initialisation (see
dev(9)), but can call it at any appropriate time, and
instead of calling intrdisable they can simply enable or
disable interrupts in the device as required.
SOURCE
/sys/src/9/*/trap.c
SEE ALSO
malloc(9), qio(9), sleep(9), splhi(9)
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