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Commit dbe7fcda authored by Jianyu Zhan's avatar Jianyu Zhan Committed by Jonathan Corbet
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Documentation/IRQ-domain.txt: Document irq_domain_create_{linear, tree} 



They have the same functionalities as irq_domain_add_{linear, tree},
except fro accepting different first argument.

Signed-off-by: default avatarJianyu Zhan <nasa4836@gmail.com>
Acked-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent 83d26b63

Documentation/IRQ-domain.txt

+12 −0
Original line number Diff line number Diff line
@@ -70,6 +70,7 @@ of the reverse map types are described below: 


==== Linear ====

irq_domain_add_linear()

irq_domain_create_linear()



The linear reverse map maintains a fixed size table indexed by the

hwirq number.  When a hwirq is mapped, an irq_desc is allocated for
@@ -81,10 +82,16 @@ map are fixed time lookup for IRQ numbers, and irq_descs are only 
allocated for in-use IRQs.  The disadvantage is that the table must be

as large as the largest possible hwirq number.



irq_domain_add_linear() and irq_domain_create_linear() are functionally

equivalent, except for the first argument is different - the former

accepts an Open Firmware specific 'struct device_node', while the latter

accepts a more general abstraction 'struct fwnode_handle'.



The majority of drivers should use the linear map.



==== Tree ====

irq_domain_add_tree()

irq_domain_create_tree()



The irq_domain maintains a radix tree map from hwirq numbers to Linux

IRQs.  When an hwirq is mapped, an irq_desc is allocated and the
@@ -95,6 +102,11 @@ since it doesn't need to allocate a table as large as the largest 
hwirq number.  The disadvantage is that hwirq to IRQ number lookup is

dependent on how many entries are in the table.



irq_domain_add_tree() and irq_domain_create_tree() are functionally

equivalent, except for the first argument is different - the former

accepts an Open Firmware specific 'struct device_node', while the latter

accepts a more general abstraction 'struct fwnode_handle'.



Very few drivers should need this mapping.



==== No Map ===-