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irq_domain: Standardise legacy/linear domain selection

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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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Documentation/IRQ-domain.txt
+5
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@@ -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.