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authorMark Brown <broonie@opensource.wolfsonmicro.com>2012-07-05 07:19:19 -0400
committerGrant Likely <grant.likely@secretlab.ca>2012-07-11 09:59:17 -0400
commit781d0f46d81e2c26c70649903b503bcfe817efc8 (patch)
tree11794b64c41e8468db6d14243c5becce3b5b64c8 /Documentation
parentaed98048bd1c83469d96932c1901e867d9ba519a (diff)
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>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/IRQ-domain.txt5
1 files changed, 5 insertions, 0 deletions
diff --git a/Documentation/IRQ-domain.txt b/Documentation/IRQ-domain.txt
index 27dcaabfb4db..1401cece745a 100644
--- a/Documentation/IRQ-domain.txt
+++ b/Documentation/IRQ-domain.txt
@@ -93,6 +93,7 @@ Linux IRQ number into the hardware.
93Most drivers cannot use this mapping. 93Most drivers cannot use this mapping.
94 94
95==== Legacy ==== 95==== Legacy ====
96irq_domain_add_simple()
96irq_domain_add_legacy() 97irq_domain_add_legacy()
97irq_domain_add_legacy_isa() 98irq_domain_add_legacy_isa()
98 99
@@ -115,3 +116,7 @@ The legacy map should only be used if fixed IRQ mappings must be
115supported. For example, ISA controllers would use the legacy map for 116supported. For example, ISA controllers would use the legacy map for
116mapping Linux IRQs 0-15 so that existing ISA drivers get the correct IRQ 117mapping Linux IRQs 0-15 so that existing ISA drivers get the correct IRQ
117numbers. 118numbers.
119
120Most users of legacy mappings should use irq_domain_add_simple() which
121will use a legacy domain only if an IRQ range is supplied by the
122system and will otherwise use a linear domain mapping.