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

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Date:   Wed, 2 Nov 2016 09:29:22 +0100
From:   Ondrej Zary <linux@...nbow-software.org>
To:     Finn Thain <fthain@...egraphics.com.au>
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 Wednesday 02 November 2016, Finn Thain wrote:
> On Mon, 31 Oct 2016, Ondrej Zary wrote:
> > Find free and working IRQ automatically on HP C2502 cards.
> > Also allow IRQ 9 to work (aliases to IRQ 2 on the card).
> >
> > Signed-off-by: Ondrej Zary <linux@...nbow-software.org>
> > ---
> >  drivers/scsi/g_NCR5380.c |   29 +++++++++++++++++++++++++++--
> >  1 file changed, 27 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/scsi/g_NCR5380.c b/drivers/scsi/g_NCR5380.c
> > index e713dba..27fc499 100644
> > --- a/drivers/scsi/g_NCR5380.c
> > +++ b/drivers/scsi/g_NCR5380.c
> > @@ -156,6 +156,8 @@ static void magic_configure(int idx, u8 irq, u8
> > magic[]) outb(magic[4], 0x379);
> >
> >  	/* allowed IRQs for HP C2502 */
> > +	if (irq == 9)
> > +		irq = 2;
> >  	if (irq != 2 && irq != 3 && irq != 4 && irq != 5 && irq != 7)
> >  		irq = 0;
> >  	if (idx >= 0 && idx <= 7)
> > @@ -163,6 +165,21 @@ static void magic_configure(int idx, u8 irq, u8
> > magic[]) outb(cfg, 0x379);
> >  }
> >
> > +/* find a free and working IRQ (for HP C2502) */
> > +static int NCR5380_find_irq(struct Scsi_Host *instance, u8 irqs[],
> > +			    int port_idx, u8 magic[])
> > +{
> > +	int i;
> > +
> > +	for (i = 0; irqs[i]; i++) {
> > +		magic_configure(port_idx, irqs[i], magic);
> > +		if (NCR5380_test_irq(instance, irqs[i]) == 0)
> > +			return irqs[i];
>
> The NCR5380_test_irq routine in patch 2/6 doesn't work for shared irqs, so
> you may not get the IRQ you would expect. (The core driver does support
> shared irqs, BTW.)

ISA bus does not support IRQ sharing.

> 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.

> 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.

> 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.
>
> > +	}
> > +	magic_configure(port_idx, 0, magic);
> > +	return NO_IRQ;
> > +}
> > +
> >  static unsigned int ncr_53c400a_ports[] = {
> >  	0x280, 0x290, 0x300, 0x310, 0x330, 0x340, 0x348, 0x350, 0
> >  };
> > @@ -175,6 +192,9 @@ static void magic_configure(int idx, u8 irq, u8
> > magic[]) static u8 hp_c2502_magic[] = {	/* HP C2502 */
> >  	0x0f, 0x22, 0xf0, 0x20, 0x80
> >  };
> > +static u8 hp_c2502_irqs[] = {
> > +	9, 5, 7, 3, 4, 0
> > +};
> >
> >  static int generic_NCR5380_init_one(struct scsi_host_template *tpnt,
> >  			struct device *pdev, int base, int irq, int board)
> > @@ -345,8 +365,13 @@ static int generic_NCR5380_init_one(struct
> > scsi_host_template *tpnt,
> >
> >  	if (irq != IRQ_AUTO)
> >  		instance->irq = irq;
> > -	else
> > -		instance->irq = NCR5380_probe_irq(instance);
> > +	else {
> > +		if (board == BOARD_HP_C2502)
> > +			instance->irq = NCR5380_find_irq(instance,
> > +						hp_c2502_irqs, port_idx, magic);
> > +		else
> > +			instance->irq = NCR5380_probe_irq(instance);
> > +	}
> >
> >  	/* Compatibility with documented NCR5380 kernel parameters */
> >  	if (instance->irq == 255)



-- 
Ondrej Zary