Hi Dave,
I have confirmed the execution has go into
desc <http://lxr.linux.no/linux+*/+code=desc>->irq_data
<http://lxr.linux.no/linux+*/+code=irq_data>.chip
<http://lxr.linux.no/linux+*/+code=chip>->irq_disable
<http://lxr.linux.no/linux+*/+code=irq_disable>(&desc
<http://lxr.linux.no/linux+*/+code=desc>->irq_data
<http://lxr.linux.no/linux+*/+code=irq_data>);
However, irq_disable points to kernel/irq/chip.c:default_disable() which do
nothings.
Unlike default_enable() which called by enable_irq() will unmask the IRQ
accordingly.
I don't understand the reason behind.
BR,
Jacky
On 3/3/2011 6:49 AM, Dave Hylands wrote:
Hi Jacky,
Sending to the list as well.
On Tue, Mar 1, 2011 at 1:55 AM, Jacky Lam<[email protected]> wrote:
Hi,
It's long before when I want to enable/disable an interrupt, I call
enable_irq()/disable_irq(). However, recently, I do that again.
disable_irq() do nothing. I looked into the code and find disable_irq()
is pointing to a empty function default_disable(). This change is
started from 2.6.20.
I want to know what should I do if I want to disable an interrupt now?
So disable/enable_irq are nestable, and you're expected to call them
in the order disable/enable.
You need to call enable_irq exactly the same number of times that you
call disable_irq.
If you start wth inerrtupts enabled and do
enable_irq
...do some stuff...
disable_irq
then disable_irq will do nothing since it just decremented the count
that enable_irq incremented.
Another way of looking at it is that disable_irq increments a count,
and enable_irq decrements a count.
The interrupt is only "really" disabled when the count transitions
from 0 to 1, and the interrupt is only "really" enabled when the count
transitions from 1 to 0.
Dave Hylands
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