Re: [PATCH] ISA Plug-n-Play support for 2.3.28

Andrey Panin (pazke@orbita.don.sitek.net)
Wed, 17 Nov 1999 10:59:33 +0300

Theodore Y. Ts'o wrote:
>
> Andrey,
>
> Thanks for the ISA Plug-n-Play serial support. One quick question; why
> the request_irq() / free_irq()? Is this to avoid the IRQ assignment
> from grabbing an IRQ already used by another serial port? If so, does
> this mean that the ISA Plug-n-Play boards can never share IRQ's with
> another port, even if they are on the same board?
>
> - Ted

Hi.

Now request_irq() / free_irq() pair prevents unnecessary irq sharing (PNP
resource
manager assigns not irq_request()'ed IRQ's, even if these IRQ's are really used
by another
serial ports and free IRQ's exist).

About IRQ sharing, I'm not hardware guru and I don't now how ISA IRQ can be
shared or not shared.

If IRQ sharing is possible, then next I want to implement such algorithm:
- first try to get free IRQ;
- if dev->prepare() / dev->activate() failed (this most probably means that
here is no free IRQ),
then let PNP resource manager assign IRQ and repeat device activation with
shared IRQ.

Andrey

P.S. Sorry for my bad English :(

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