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

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Message-ID: <alpine.LNX.2.00.1611011258090.25806@nippy.intranet>
Date:   Wed, 2 Nov 2016 18:46:44 +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 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.)

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.

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 user asks for IRQ_AUTO, just configure the board for a hard-coded 
default, say 9, and print a warning message to say so.

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)
> 

--