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doc: add summary table for kernel data passing

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Add a table summarizing the key characteristics of each
of the data passing objects.

It is useful for readers to have an overview they can skim without
having to read each section in detail.

Signed-off-by: Marti Bolivar <marti.bolivar@nordicsemi.no>
This commit is contained in:
Marti Bolivar 2019-08-27 18:30:11 -06:00 • committed by Ioannis Glaropoulos
commit 1e34ea950c
1 changed files with 26 additions and 1 deletions
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27
doc/reference/kernel/index.rst
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@ -40,9 +40,34 @@ synchronization.
Data Passing
************
These pages cover kernel services which can be used to pass data between
These pages cover kernel objects which can be used to pass data between
threads and ISRs.
The following table summarizes their high-level features.
=============== ============== =================== ============== ============== ================= ============== ===============================
Object Bidirectional? Data structure Data item size Data Alignment ISRs can receive? ISRs can send? Overrun handling
=============== ============== =================== ============== ============== ================= ============== ===============================
FIFO No Queue Arbitrary [1] 4 B [2] Yes [3] Yes N/A
LIFO No Queue Arbitrary [1] 4 B [2] Yes [3] Yes N/A
Stack No Array Word Word Yes [3] Yes Undefined behavior
Message queue No Ring buffer Power of two Power of two Yes [3] Yes Pend thread or return -errno
Mailbox Yes Queue Arbitrary [1] Arbitrary No No N/A
Pipe No Ring buffer [4] Arbitrary Arbitrary No No Pend thread or return -errno
=============== ============== =================== ============== ============== ================= ============== ===============================
[1] Callers allocate space for queue overhead in the data
elements themselves.
[2] Objects added with k_fifo_alloc_put() and k_lifo_alloc_put()
do not have alignment constraints, but use temporary memory from the
calling thread's resource pool.
[3] ISRs can receive only when passing K_NO_WAIT as the timeout
argument.
[4] Optional.
.. toctree::
:maxdepth: 2