[PATCH] Documentation/IRQ-domain.txt: Document irq_domain_create_{linear, tree}

Jianyu Zhan
2016-03-26T13:07:37Z

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

Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
---
Documentation/IRQ-domain.txt | 12 ++++++++++++
1 file changed, 12 insertions(+)

diff --git a/Documentation/IRQ-domain.txt b/Documentation/IRQ-domain.txt
index 8d990bd..89dda22 100644
--- a/Documentation/IRQ-domain.txt
+++ b/Documentation/IRQ-domain.txt
@@ -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 abstration '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 abstration 'struct fwnode_handle'.
+
Very few drivers should need this mapping.

==== No Map ===-
--
2.4.3