handle_level_irq 与handle_edge_irq 的区别【转】

转自:http://blog.csdn.net/xavierxiao/article/details/6087277

Linux 里，

handle_level_irq

 *    Level type interrupts are active as long as the hardware line has
 *    the active level. This may require to mask the interrupt and unmask
 *    it after the associated handler has acknowledged the device, so the
 *    interrupt line is back to inactive.

     当中断线电平达到激活电平，中断一直会被激活。 所以需要刚进中断处理函数就要屏蔽掉中断，

等handler 处理完后再打开中断(unmask)

 Pesudo code

      由于irq在整个处理过程中都被屏蔽，所以需要handle_level_irq里的action要尽量简短

handle_edge_irq

 *    Interrupt occures on the falling and/or rising edge of a hardware
 *    signal. The occurence is latched into the irq controller hardware
 *    and must be acked in order to be reenabled. After the ack another
 *    interrupt can happen on the same source even before the first one
 *    is handled by the assosiacted event handler. If this happens it
 *    might be necessary to disable (mask) the interrupt depending on the
 *    controller hardware. This requires to reenable the interrupt inside
 *    of the loop which handles the interrupts which have arrived while
 *    the handler was running. If all pending interrupts are handled, the
 *    loop is left.

    中断发生在上升沿/下降沿， 它会被中断控制器锁存起来，需要ack 后才能重新使能。 Ack 后新的

中断可以在前一个中断正在被处理时产生，如果这种情况发生，则需要屏蔽中断。同时，需要用一个loop

来处理中断处理过程中又有中断产生的情况，在这个loop中重新把中断屏蔽打开。 如果所有pending的

中断都处理完了，loop就可以离开。

Pesudo code

中断触发方式的比较

http://blog.21ic.com/user1/2662/archives/2007/37347.html