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Commit dbe7fcda authored by Jianyu Zhan's avatar Jianyu Zhan Committed by Jonathan Corbet
Browse files

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




==== Linear ====

==== Linear ====

irq_domain_add_linear()

irq_domain_add_linear()

irq_domain_create_linear()





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

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

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

allocated for in-use IRQs.  The disadvantage is that the table must be

as large as the largest possible hwirq number.

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.

The majority of drivers should use the linear map.





==== Tree ====

==== Tree ====

irq_domain_add_tree()

irq_domain_add_tree()

irq_domain_create_tree()





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

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

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

hwirq number.  The disadvantage is that hwirq to IRQ number lookup is

dependent on how many entries are in the table.

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.

Very few drivers should need this mapping.





==== No Map ===-

==== No Map ===-