107 lines
3 KiB
Plaintext
107 lines
3 KiB
Plaintext
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.TH INTRENABLE 9
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.SH NAME
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intrenable, intrdisable \- enable (disable) an interrupt handler
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.SH SYNOPSIS
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.ta \w'\fLvoid* 'u
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.B
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void intrenable(int v, void (*f)(Ureg*, void*), void* a, int tbdf, char *name)
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.PP
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.B
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void intrdisable(int v, void (*f)(Ureg*, void*), void* a, int tbdf, char *name)
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.SH DESCRIPTION
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.I Intrenable
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registers
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.I f
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to be called by the kernel's interrupt controller driver each time
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an interrupt denoted by
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.I v
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occurs, and unmasks the corresponding interrupt in the interrupt controller.
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The encoding of
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.I v
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is platform-dependent; it is often an interrupt vector number, but
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can be more complex.
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.I Tbdf
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is a platform-dependent value that might further qualify
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.IR v .
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It might for instance
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denote the type of bus, bus instance, device number and function
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(following the PCI device indexing scheme), hence its name,
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but can have platform-dependent meaning.
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.I Name
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is a string that should uniquely identify the corresponding device (eg, \f5"uart0"\fP);
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again it is usually platform-dependent.
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.I Intrenable
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supports sharing of interrupt levels when the hardware does.
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.PP
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Almost invariably
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.I f
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is a function defined in a device driver to carry out the device-specific work associated with a given interrupt.
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The pointer
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.I a
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is passed to
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.IR f ;
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typically it points to the driver's data for a given device or controller.
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It also passes
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.I f
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a
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.B Ureg*
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value that
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contains the registers saved by the interrupt handler (the
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contents are platform specific;
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see the platform's include file
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.BR "ureg.h" ).
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.PP
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.I F
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is invoked by underlying code in the kernel that is invoked directly from the hardware vectors.
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It is therefore not running in any process (see
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.IR kproc (9);
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indeed, on many platforms
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the current process pointer
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.RB ( up )
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will be nil.
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There are many restrictions on kernel functions running outside a process, but a fundamental one is that
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they must not
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.IR sleep (9),
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although they often call
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.B wakeup
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to signal the occurrence of an event associated with the interrupt.
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.IR Qio (9)
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and other manual pages note which functions are safe for
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.I f
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to call.
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.PP
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The interrupt controller driver does whatever is
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required to acknowledge or dismiss the interrupt signal in the interrupt controller,
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before calling
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.IR f ,
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for edge-triggered interrupts,
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and after calling
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.I f
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for level-triggered ones.
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.I F
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is responsible for dealing with the cause of the interrupt in the device, including any
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acknowledgement required in the device, before it returns.
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.PP
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.I Intrdisable
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removes any registration previously made by
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.I intrenable
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with matching parameters, and if no other
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interrupt is active on
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.IR v ,
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it masks the interrupt in the controller.
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Device drivers that are not dynamically configured tend to call
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.I intrenable
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during reset or initialisation (see
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.IR dev (9)),
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but can call it at any appropriate time, and
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instead of calling
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.I intrdisable
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they can simply enable or disable interrupts in the device as required.
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.SH SOURCE
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.B /sys/src/9/*/trap.c
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.SH SEE ALSO
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.IR malloc (9),
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.IR qio (9),
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.IR sleep (9),
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.IR splhi (9)
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