Re: [PATCH v2] relay: Add global mode support for buffer-only channels

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 11 Jul 2016 12:47:36 +0530 akash.goel@intel.com wrote:

> From: Akash Goel <akash.goel@intel.com>
> 
> The following patch added support to use channels with no associated files.
> 	relay: add buffer-only channels; useful for early logging

hm, 8 years ago.  Normally we refer to previous commits using the form
20d8b67c06fa5e74f44e ("relay: add buffer-only channels; useful for
early logging").  But this one is so old that we should inform readers
about its vintage, so this form:

commit 20d8b67c06fa5e74f44e80b0a0fd68c8327f7c6a
Author: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Date:   Fri Jul 25 19:45:12 2008 -0700

    relay: add buffer-only channels; useful for early logging

would be better.

> This is useful when the exact location of relay file is not known or the
> the parent directory of relay file is not available, while creating the
> channel and the logging has to start right from the boot.
> 
> But there was no provision to use global mode with buffer-only channels,
> which is added by this patch, without modifying the interface where initially
> there will be a dummy invocation of create_buf_file callback through which
> kernel client can convey the need of a global buffer.
> 
> For the use case where drivers/kernel clients want a simple interface for the
> userspace, which enables them to capture data/logs from relay file in order &
> without any post processing, support of Global buffer mode is warranted.
>
> ...
>
> @@ -706,6 +727,7 @@ int relay_late_setup_files(struct rchan *chan,
>  
>  	return err;
>  }
> +EXPORT_SYMBOL_GPL(relay_late_setup_files);

The export is unneeded and undocumented.