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2008-08-04 Joel Sherrill <joel.sherrill@OARcorp.com>

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PR 1263/doc
	* user/part.t: Improve discussion of alignment and minimum buffer
	sizes.
This commit is contained in:
Joel Sherrill
2008-08-04 20:45:38 +00:00
parent 2bc42d1da6
commit 17f5f2245b
2 changed files with 19 additions and 7 deletions
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6
doc/ChangeLog
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@@ -1,3 +1,9 @@
2008-08-04 Joel Sherrill <joel.sherrill@OARcorp.com>
PR 1263/doc
* user/part.t: Improve discussion of alignment and minimum buffer
sizes.
2008-08-04 Joel Sherrill <joel.sherrill@OARcorp.com>
PR 1288/doc

20
doc/user/part.t
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@@ -1,5 +1,5 @@
@c
@c COPYRIGHT (c) 1988-2002.
@c COPYRIGHT (c) 1988-2008.
@c On-Line Applications Research Corporation (OAR).
@c All rights reserved.
@c
@@ -39,9 +39,9 @@ allocated and deallocated.
Partitions are managed and maintained as a list of
buffers. Buffers are obtained from the front of the partition's
free buffer chain and returned to the rear of the same chain.
When a buffer is on the free buffer chain, RTEMS uses eight
bytes of each buffer as the free buffer chain. When a buffer is
allocated, the entire buffer is available for application use.
When a buffer is on the free buffer chain, RTEMS uses two
pointers of memory from each buffer as the free buffer chain.
When a buffer is allocated, the entire buffer is available for application use.
Therefore, modifying memory that is outside of an allocated
buffer could destroy the free buffer chain or the contents of an
adjacent allocated buffer.
@@ -187,7 +187,7 @@ This directive creates a partition of fixed size
buffers from a physically contiguous memory space which starts
at starting_address and is length bytes in size. Each allocated
buffer is to be of @code{buffer_size} in bytes. The assigned
partition id is returned in id. This partition id is used to
partition id is returned in @code{id}. This partition id is used to
access the partition with other partition related directives.
For control and maintenance of the partition, RTEMS allocates a
PTCB from the local PTCB free pool and initializes it.
@@ -197,8 +197,14 @@ PTCB from the local PTCB free pool and initializes it.
This directive will not cause the calling task to be
preempted.
The starting_address and buffer_size parameters must
be multiples of four.
The @code{starting_address} must be properly aligned for the
target architecture.
Th @code{buffer_size} parameter must be a multiple of
the CPU alignment factor. Additionally, @code{buffer_size}
must be large enough to hold two pointers on the target
architecture. This is required for RTEMS to manage the
buffers when they are free.
Memory from the partition is not used by RTEMS to
store the Partition Control Block.