Hi Wolfgang,
On 20 September 2017 at 13:55, Wolfgang Denk wd@denx.de wrote:
Dear Simon,
sorry for jumping in so late...
In message 20170916212331.170463-1-sjg@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