What is meant by chained interrupt handlers, when to use them.

What is meant by chained interrupt handlers, when to use them.

[Valmiki]

I'm seeing that chained_irq_enter/exit functions are being used in cained 
irq handlers. 

These chained_irq_enter/exit functions are doing ack, mask, unmask 
functions from irq chip. 
Already when an interrupt handler is being executed that IRQ line will be 
disabled by linux, so what is the purpose of masking/unmasking them.

What is term chained referring to, does it mean reading interrupt status 
register and check for bit set one after and another handle that 
corresponding IRQ, so in a chain fashion.

Valmiki

Re: What is meant by chained interrupt handlers, when to use them.

[Valmiki]

Valmiki <valmikibow <at> gmail.com> writes:

> 
> I'm seeing that chained_irq_enter/exit functions are being used in 
cained 
> irq handlers. 
> 
> These chained_irq_enter/exit functions are doing ack, mask, unmask 
> functions from irq chip. 
> Already when an interrupt handler is being executed that IRQ line will 
be 
> disabled by linux, so what is the purpose of masking/unmasking them.
> 
> What is term chained referring to, does it mean reading interrupt 
status 
> register and check for bit set one after and another handle that 
> corresponding IRQ, so in a chain fashion.


When we use irq_set_chained_handler the irq line will not be disabled, 
unlike request_irq ? 
If that is the case calling chained_irq_enter which does mask/unmask to 
only current irq line, but i see in some pcie root port drivers after 
calling this they are handling all the available interrupts but only one 
is masked ? Is this method correct ?

> 
> Valmiki
> 
>