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irq_domain: Standardise legacy/linear domain selection 

A large proportion of interrupt controllers that support legacy mappings
do so because non-DT systems need to use fixed IRQ numbers when registering
devices via buses but can otherwise use a linear mapping. The interrupt
controller itself typically is not affected by the mapping used and best
practice is to use a linear mapping where possible so drivers frequently
select at runtime depending on if a legacy range has been allocated to
them.

Standardise this behaviour by providing irq_domain_register_simple() which
will allocate a linear mapping unless a positive first_irq is provided in
which case it will fall back to a legacy mapping. This helps make best
practice for irq_domain adoption clearer.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
This commit is contained in:
Mark Brown 2012-07-05 12:19:19 +01:00 committed by Grant Likely
parent aed98048bd
commit 781d0f46d8
3 changed files with 40 additions and 0 deletions
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5
Documentation/IRQ-domain.txt
View File

@ -93,6 +93,7 @@ Linux IRQ number into the hardware.
Most drivers cannot use this mapping.
==== Legacy ====
irq_domain_add_simple()
irq_domain_add_legacy()
irq_domain_add_legacy_isa()
@ -115,3 +116,7 @@ The legacy map should only be used if fixed IRQ mappings must be
supported. For example, ISA controllers would use the legacy map for
mapping Linux IRQs 0-15 so that existing ISA drivers get the correct IRQ
numbers.
Most users of legacy mappings should use irq_domain_add_simple() which
will use a legacy domain only if an IRQ range is supplied by the
system and will otherwise use a linear domain mapping.

5
include/linux/irqdomain.h
View File

@ -112,6 +112,11 @@ struct irq_domain {
};
#ifdef CONFIG_IRQ_DOMAIN
struct irq_domain *irq_domain_add_simple(struct device_node *of_node,
unsigned int size,
unsigned int first_irq,
const struct irq_domain_ops *ops,
void *host_data);
struct irq_domain *irq_domain_add_legacy(struct device_node *of_node,
unsigned int size,
unsigned int first_irq,

30
kernel/irq/irqdomain.c
View File

@ -139,6 +139,36 @@ static unsigned int irq_domain_legacy_revmap(struct irq_domain *domain,
return hwirq - first_hwirq + domain->revmap_data.legacy.first_irq;
}
/**
* irq_domain_add_simple() - Allocate and register a simple irq_domain.
* @of_node: pointer to interrupt controller's device tree node.
* @size: total number of irqs in mapping
* @first_irq: first number of irq block assigned to the domain
* @ops: map/unmap domain callbacks
* @host_data: Controller private data pointer
*
* Allocates a legacy irq_domain if irq_base is positive or a linear
* domain otherwise.
*
* This is intended to implement the expected behaviour for most
* interrupt controllers which is that a linear mapping should
* normally be used unless the system requires a legacy mapping in
* order to support supplying interrupt numbers during non-DT
* registration of devices.
*/
struct irq_domain *irq_domain_add_simple(struct device_node *of_node,
unsigned int size,
unsigned int first_irq,
const struct irq_domain_ops *ops,
void *host_data)
{
if (first_irq > 0)
return irq_domain_add_legacy(of_node, size, first_irq, 0,
ops, host_data);
else
return irq_domain_add_linear(of_node, size, ops, host_data);
}
/**
* irq_domain_add_legacy() - Allocate and register a legacy revmap irq_domain.
* @of_node: pointer to interrupt controller's device tree node.