linux-kernel - Re: [PATCH 4/6] g_NCR5380: Add IRQ auto-configuration for HP C2502

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Date:   Thu, 3 Nov 2016 13:17:18 +1100 (AEDT)
From:   Finn Thain <fthain@...egraphics.com.au>
To:     Ondrej Zary <linux@...nbow-software.org>
cc:     Christoph Hellwig <hch@...radead.org>, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/6] g_NCR5380: Add IRQ auto-configuration for HP C2502


On Wed, 2 Nov 2016, Ondrej Zary wrote:

> > Also, you've ignored the irq module parameters. From the user's point 
> > of view, surely the least surprising thing is to attempt to configure 
> > the card for whatever irq the user asked for.
> 
> I haven't. NCR5380_find_irq is only called when irq is set to IRQ_AUTO.
> 

My mistake.

> > If the specified irq isn't supported by the board, just log an error 
> > and fail. If you want to be user friendly, print a message to tell 
> > them what irqs the card supports.
> 
> If the IRQ is not supported (or does not work), user gets a warning and 
> the driver continues with IRQ disabled.
> 
> > If the user asks for IRQ_AUTO, just configure the board for a 
> > hard-coded default, say 9, and print a warning message to say so.
> 
> The card is almost Plug&Play. The base address is already configured 
> automatically by the driver so doing the same for IRQ makes sense.

Why don't we see any other drivers doing this?

If the card was really plug and play, I expect we would just call 
pnp_irq(), as the other PNP drivers do.

> 
> > Either way, if request_irq fails just continue with NO_IRQ, as per 
> > usual.
> >
> > To me that's the most flexible and least surprising behaviour. But 
> > again, if someone with more ISA knowledge wishes to weigh in, that's 
> > fine too.

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