Add ring buffer support

[zephyrbot]

Reported by Benjamin Walsh:

A potpourri of ring buffer-related work items.

Need to decide if ring buffer is a "first class" kernel object (i.e. like a fifo) or not (i.e. like a linked list, which is a "misc" object).
If not:
    Update the Kernel Primer to remove any mention of it. (Although where it would be documented is unclear ...)
    Move ring_buffer.c into "misc" directory.
If so:
    Include file should be relocated, since it doesn't belong under "include/misc".
    Currently lacks concurrent use protection mechanism, unlike other "first class" kernel objects. (This seems to be a deliberate choice, but is it desirable?)
    Currently unclear if ISRs can use ring buffers.
    Kernel Primer documentation should be brought into line with description for other kernel objects.

(Imported from Jira ZEP-918)

[zephyrbot]

by Sharron LIU:

As the issues was resolved with "Won't Do", according to the description of this story, "ring buffer" supposed to be excluded from https://www.zephyrproject.org/doc/kernel_v2/kernel.html
Dmitriy Korovkin , is that change on the way? Thanks.

[zephyrbot]

by Sharron LIU:

The status till git revision 19f2884:

• header file is under "include/misc/ring_buffer.h", unlike other "first-class" kernel objs.
• implementation is under "kernel/unified/ring_buffer.c", like other "first-class" kernel objs.
• ring buffer still kept TBD in the kernel primer v2 doc

This does not seem inline with the description of this story. Dmitriy Korovkin , Benjamin Walsh , could you update if any new conclusion reached to resolve the story as "Won't Do"? Thanks.

The current status is a little bit confusing if ring buffer is treated as "first-class" or not...

[zephyrbot]

by Dmitriy Korovkin:

Per discussion, ring buffer will be kept in the kernel as a simple tool for kernel developers. "Won't do" means that ring buffers are not going to be exported as a public kernel object available for application developers, as the community do not see any need for this.

[zephyrbot]

by Sharron LIU:

That's clear now. Does it mean to remove ring buffer from "kernel primer v2"?

Closing per Dmitriy Korovkin clarification.