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| author | Mark Brown <broonie@opensource.wolfsonmicro.com> | 2012-07-05 13:19:19 +0200 |
|---|---|---|
| committer | Grant Likely <grant.likely@secretlab.ca> | 2012-07-11 15:59:17 +0200 |
| commit | 781d0f46d81e2c26c70649903b503bcfe817efc8 (patch) | |
| tree | 11794b64c41e8468db6d14243c5becce3b5b64c8 /Documentation | |
| parent | irqdomain: Make ops->map hook optional (diff) | |
| download | linux-781d0f46d81e2c26c70649903b503bcfe817efc8.tar.xz linux-781d0f46d81e2c26c70649903b503bcfe817efc8.zip | |
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.txt | 5 |
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. 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. |