[U-Boot] [PATCH 00/13] log: Add a new logging feature

[Simon Glass]

Hi Wolfgang,

On 20 September 2017 at 13:55, Wolfgang Denk <wd at denx.de> wrote:
> Dear Simon,
>
> sorry for jumping in so late...
>
> In message <20170916212331.170463-1-sjg at chromium.org> you wrote:
>>
>> At present U-Boot has a logbuffer feature which records output in a memory
>> buffer for later display or storage. This is useful but is not at present
>> enabled for any board.
>
> Background explanation:  When this was implemented, the buffer
> handling was fully compatible with the Linux kernel logbuffer.
> And U-Boot was able to reserve memory (at the top of the RAM) that
> could be shared between U-Boot and Linux, so you could for example
> write U-Boot POST results into the log buffer, and read it using
> standard syslog tools in Linux.  Or keep the panic messages of the
> previous crash and read it after reboot.
>
> IIRC this was in production use only on Power architectre systems,
> and it broke (and nover got fixed) when the Linux log buffer was
> reworked.

OK I see, i did not realise the Linux connection.

>
>> This series introduced a new logging system which supports:
>> - various log levels from panic to debug
>> - log categories including all uclasses and a few others
>> - log drivers to which all log records can be sent
>> - log filters which control which log records make it to which drivers
>
> You don't mention it here, but would it be possible to keep
> compatibility with the Linux logbuffer implementation in mind?
>
> So we could re-implement this shared logbuffer thingy in case
> someone finds it useful?

I think it would be fairly easy to do, yes. It just needs a driver
which writes log records into memory at a given address. I certainly
don't like removing useful features, will take a look.

Regards,
Simon