[Buildroot] [PATCH 07/24 v4] manual: document dependencies on atomic operations

[Thomas De Schampheleire]

"Yann E. MORIN" <yann.morin.1998 at free.fr> schreef:
>Thomas, All,
>
>On 2014-08-17 15:01 +0200, Thomas De Schampheleire spake thusly:
>> "Yann E. MORIN" <yann.morin.1998 at free.fr> schreef:
>> >From: Anton Kolesov <anton.kolesov at synopsys.com>
>> >
>> >Add atomic operations to the list of generic dependencies.
>> >
>> >Since this is an architecture option, there is no comment string to be
>> >added.
>> >
>> >Signed-off-by: Anton Kolesov <Anton.Kolesov at synopsys.com>
>> >[yann.morin.1998 at free.fr: use the new arch-option; remove comment string]
>> >Signed-off-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
>> >---
>> > docs/manual/adding-packages-directory.txt | 4 ++++
>> > 1 file changed, 4 insertions(+)
>> >
>> >diff --git a/docs/manual/adding-packages-directory.txt b/docs/manual/adding-packages-directory.txt
>> >index 93e6a3e..40a81d5 100644
>> >--- a/docs/manual/adding-packages-directory.txt
>> >+++ b/docs/manual/adding-packages-directory.txt
>> >@@ -219,6 +219,10 @@ use in the comment.
>> > ** Dependency symbol: +BR2_USE_MMU+
>> > ** Comment string: no comment to be added
>> > 
>> >+* Atomic operations
>> >+** Dependency symbol: +BR2_ARCH_HAS_ATOMICS+
>> >+** Comment string: no comment to be added
>> >+
>> 
>> Should we provide a brief explanation, reference, or
>>  name of these functions to make it a bit clearer what
>> is meant with 'atomic operations'?
>
>Well, the atomics are all named differently in different architectures.
>
>For example, armv6+ has LDREX and STREX (amon others):
>    http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dht0008a/ch01s02s01.html
>
>While on x86, I don't think there are corresponding instructions, but
>you can prefix some intructions with the LOCK prefix to achieve a
>similar result.
>
>So, I would not know what to put in here. Also, we do not explain what
>the other options are (like MMU, for example). Why would we do that for
>this specific option, and not others?


Because MMU is a widely known acronym for anyone in the embedded world, but 'atomics' or 'atomic operations' is a much more general term that is less obvious, IMHO.

Maybe the description can clarify that we're talking about a dependency on _CPU_ atomic _instructions_?