Re: [RFC] [PATCH 02/62] mpu401:snd_mpu401_uart_new(): split semantic of irq_flags

Yong Zhang
2011-09-08T13:37:22Z

On Thu, Sep 08, 2011 at 12:53:14PM +0200, Clemens Ladisch wrote:
> Yong Zhang wrote:
> > Now snd_mpu401_uart_new() parameter 'irq_flags' take two role
> > in it: one is the condition to request_irq and the other is
> > the real irq_flags which will be transfered to request_irq().
> >
> > So add another parameter 'want_irq' to take the role of the
> > first one, this will make it easy to remove IRQF_DISABLED.
>
> Please note that the irq number is also intended to pass this
> information:

Yes.

this is a bit subtle:
* @irq: the irq number, -1 if no interrupt for mpu

This semantic of 'irq' is kept by the callers IMHO.

* @irq_flags: the irq request flags (SA_XXX), 0 if irq was already reserved.

So irq_flags has other meaning--if the irq is already reserved.
Maybe my imprecise description make some kind of misunderstanding.

Seems 'irq_reserved' is more meaningful than 'want_irq', yes?

>
> > * @irq: the irq number, -1 if no interrupt for mpu
> > ...
> > - if (irq >= 0 && irq_flags) {
> > if (request_irq(irq, snd_mpu401_uart_interrupt, irq_flags,
>
> Of course, most of snd_mpu401_uart_new()'s users get this wrong and use
> 0 instead of -1, relying on the irq_flags parameter only. But if these
> are fixed to use irq == -1, we get the same effect without having to
> introduce another parameter.

Hmm, precisely IRQF_DISABLED imply irq is not reserved in some caller.

BTW, I'm not familiar with mpu401, so maybe I'm missing something here.

Thanks,
Yong