Subject: Re: [RFC 12/14] irq_domain: Add support for base irq and hwirq in legacy mappings

From: Rob Herring <[email-masked]>
Date: Thu, 12 Jan 2012 18:37:25 -0600

On 01/11/2012 02:22 PM, Grant Likely wrote:
> Add support for a legacy mapping where irq = (hwirq - first_hwirq + first_irq)
> so that a controller driver can allocate a fixed range of irq_descs and use
> a simple calculation to translate back and forth between linux and hw irq
> numbers.  This is needed to use an irq_domain with many of the ARM interrupt
> controller drivers that manage their own irq_desc allocations.  Ultimately
> the goal is to migrate those drivers to use the linear revmap, but doing it
> this way allows each driver to be converted separately which makes the
> migration path easier.
> 
> This patch generalizes the IRQ_DOMAIN_MAP_LEGACY method to use
> (first_irq-first_hwirq) as the offset between hwirq and linux irq number,
> and adds checks to make sure that the hwirq number does not exceed range
> assigned to the controller.
> 
> Signed-off-by: Grant Likely <[email-masked]>
> Cc: Benjamin Herrenschmidt <[email-masked]>
> ---
>  arch/powerpc/include/asm/irq.h   |    3 -
>  arch/powerpc/sysdev/i8259.c      |    2 +-
>  arch/powerpc/sysdev/tsi108_pci.c |    2 +-
>  include/linux/irqdomain.h        |   20 +++++++++-
>  kernel/irq/irqdomain.c           |   78 +++++++++++++++++++++++++-------------
>  5 files changed, 73 insertions(+), 32 deletions(-)
> 

snip...

> @@ -454,8 +477,11 @@ unsigned int irq_find_mapping(struct irq_domain *domain,
>  		return 0;
>  
>  	/* legacy -> bail early */
> -	if (domain->revmap_type == IRQ_DOMAIN_MAP_LEGACY)
> -		return hwirq;
> +	if (domain->revmap_type == IRQ_DOMAIN_MAP_LEGACY) {
> +		if (hwirq > domain->revmap_data.legacy.size)
> +			return 0;
> +		return domain->revmap_data.legacy.first_irq + hwirq;

This needs a "- domain->revmap_data.legacy.first_hwirq"

Rob

> +	}
>  
>  	/* Slow path does a linear search of the map */
>  	if (hint < NUM_ISA_INTERRUPTS)