genericirq.tmpl

linux 内核源代码

}

default_disable(irq)
{
	if (!delay_disable(irq))
		desc->chip->mask(irq);
}

default_ack(irq)
{
	chip->ack(irq);
}

default_mask_ack(irq)
{
	if (chip->mask_ack) {
		chip->mask_ack(irq);
	} else {
		chip->mask(irq);
		chip->ack(irq);
	}
}

noop(irq)
{
}

		</programlisting>
	        </para>
	    </sect3>
	</sect2>
	<sect2>
	<title>Default flow handler implementations</title>
	    <sect3>
	 	<title>Default Level IRQ flow handler</title>
		<para>
		handle_level_irq provides a generic implementation
		for level-triggered interrupts.
		</para>
		<para>
		The following control flow is implemented (simplified excerpt):
		<programlisting>
desc->chip->start();
handle_IRQ_event(desc->action);
desc->chip->end();
		</programlisting>
		</para>
   	    </sect3>
	    <sect3>
	 	<title>Default Edge IRQ flow handler</title>
		<para>
		handle_edge_irq provides a generic implementation
		for edge-triggered interrupts.
		</para>
		<para>
		The following control flow is implemented (simplified excerpt):
		<programlisting>
if (desc->status &amp; running) {
	desc->chip->hold();
	desc->status |= pending | masked;
	return;
}
desc->chip->start();
desc->status |= running;
do {
	if (desc->status &amp; masked)
		desc->chip->enable();
	desc->status &amp;= ~pending;
	handle_IRQ_event(desc->action);
} while (status &amp; pending);
desc->status &amp;= ~running;
desc->chip->end();
		</programlisting>
		</para>
   	    </sect3>
	    <sect3>
	 	<title>Default simple IRQ flow handler</title>
		<para>
		handle_simple_irq provides a generic implementation
		for simple interrupts.
		</para>
		<para>
		Note: The simple flow handler does not call any
		handler/chip primitives.
		</para>
		<para>
		The following control flow is implemented (simplified excerpt):
		<programlisting>
handle_IRQ_event(desc->action);
		</programlisting>
		</para>
   	    </sect3>
	    <sect3>
	 	<title>Default per CPU flow handler</title>
		<para>
		handle_percpu_irq provides a generic implementation
		for per CPU interrupts.
		</para>
		<para>
		Per CPU interrupts are only available on SMP and
		the handler provides a simplified version without
		locking.
		</para>
		<para>
		The following control flow is implemented (simplified excerpt):
		<programlisting>
desc->chip->start();
handle_IRQ_event(desc->action);
desc->chip->end();
		</programlisting>
		</para>
   	    </sect3>
	</sect2>
	<sect2>
	<title>Quirks and optimizations</title>
	<para>
	The generic functions are intended for 'clean' architectures and chips,
	which have no platform-specific IRQ handling quirks. If an architecture
	needs to implement quirks on the 'flow' level then it can do so by
	overriding the highlevel irq-flow handler.
	</para>
	</sect2>
	<sect2>
	<title>Delayed interrupt disable</title>
	<para>
	This per interrupt selectable feature, which was introduced by Russell
	King in the ARM interrupt implementation, does not mask an interrupt
	at the hardware level when disable_irq() is called. The interrupt is
	kept enabled and is masked in the flow handler when an interrupt event
	happens. This prevents losing edge interrupts on hardware which does
	not store an edge interrupt event while the interrupt is disabled at
	the hardware level. When an interrupt arrives while the IRQ_DISABLED
	flag is set, then the interrupt is masked at the hardware level and
	the IRQ_PENDING bit is set. When the interrupt is re-enabled by
	enable_irq() the pending bit is checked and if it is set, the
	interrupt is resent either via hardware or by a software resend
	mechanism. (It's necessary to enable CONFIG_HARDIRQS_SW_RESEND when
	you want to use the delayed interrupt disable feature and your
	hardware is not capable of retriggering	an interrupt.)
	The delayed interrupt disable can be runtime enabled, per interrupt,
	by setting the IRQ_DELAYED_DISABLE flag in the irq_desc status field.
	</para>
	</sect2>
    </sect1>
    <sect1>
	<title>Chiplevel hardware encapsulation</title>
	<para>
	The chip level hardware descriptor structure irq_chip
	contains all the direct chip relevant functions, which
	can be utilized by the irq flow implementations.
	  <itemizedlist>
	  <listitem><para>ack()</para></listitem>
	  <listitem><para>mask_ack() - Optional, recommended for performance</para></listitem>
	  <listitem><para>mask()</para></listitem>
	  <listitem><para>unmask()</para></listitem>
	  <listitem><para>retrigger() - Optional</para></listitem>
	  <listitem><para>set_type() - Optional</para></listitem>
	  <listitem><para>set_wake() - Optional</para></listitem>
	  </itemizedlist>
	These primitives are strictly intended to mean what they say: ack means
	ACK, masking means masking of an IRQ line, etc. It is up to the flow
	handler(s) to use these basic units of lowlevel functionality.
	</para>
    </sect1>
  </chapter>

  <chapter id="doirq">
     <title>__do_IRQ entry point</title>
     <para>
 	The original implementation __do_IRQ() is an alternative entry
	point for all types of interrupts.
     </para>
     <para>
	This handler turned out to be not suitable for all
	interrupt hardware and was therefore reimplemented with split
	functionality for egde/level/simple/percpu interrupts. This is not
	only a functional optimization. It also shortens code paths for
	interrupts.
      </para>
      <para>
	To make use of the split implementation, replace the call to
	__do_IRQ by a call to desc->chip->handle_irq() and associate
        the appropriate handler function to desc->chip->handle_irq().
	In most cases the generic handler implementations should
	be sufficient.
     </para>
  </chapter>

  <chapter id="locking">
     <title>Locking on SMP</title>
     <para>
	The locking of chip registers is up to the architecture that
	defines the chip primitives. There is a chip->lock field that can be used
	for serialization, but the generic layer does not touch it. The per-irq
	structure is protected via desc->lock, by the generic layer.
     </para>
  </chapter>
  <chapter id="structs">
     <title>Structures</title>
     <para>
     This chapter contains the autogenerated documentation of the structures which are
     used in the generic IRQ layer.
     </para>
!Iinclude/linux/irq.h
  </chapter>

  <chapter id="pubfunctions">
     <title>Public Functions Provided</title>
     <para>
     This chapter contains the autogenerated documentation of the kernel API functions
      which are exported.
     </para>
!Ekernel/irq/manage.c
!Ekernel/irq/chip.c
  </chapter>

  <chapter id="intfunctions">
     <title>Internal Functions Provided</title>
     <para>
     This chapter contains the autogenerated documentation of the internal functions.
     </para>
!Ikernel/irq/handle.c
!Ikernel/irq/chip.c
  </chapter>

  <chapter id="credits">
     <title>Credits</title>
	<para>
		The following people have contributed to this document:
		<orderedlist>
			<listitem><para>Thomas Gleixner<email>[e-mail]</email></para></listitem>
			<listitem><para>Ingo Molnar<email>[e-mail]</email></para></listitem>
		</orderedlist>
	</para>
  </chapter>
</book>