linux-kernel - Re: RAMOOPS: few questions

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Message-ID: <4C0622BF.8070602@gmail.com>
Date:	Wed, 02 Jun 2010 11:22:07 +0200
From:	Marco Stornelli <marco.stornelli@...il.com>
To:	Maxim Levitsky <maximlevitsky@...il.com>
CC:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: RAMOOPS: few questions

Il 01/06/2010 21:32, Maxim Levitsky ha scritto:
> Hi,
> 
> I want to switch over my own patch that does more or less the same that
> this driver.
> 
> As I see this driver uses ioremap to reserve the memory.
> However, I have a question about how to tell kernel that specific memory
> region is reserved.
> 
> Well, I use now mem=... to do so, but this wastes space, because the
> region I need can't be near end of the RAM.
> 

Have you got any particular constraints?

> I tried to use 'memmap=20M$0x70000000' on kernel command line, but that
> just makes kernel reboot.
> I think its a bug though.
> 
> Also, does this driver dupms all kernel log or only panic/oops message?

It dumps all, but there's a fixed size for each dump, so you can see the
panic/oops information and the latest prints of the kernel before
panic/oops.

> My patch actually makes kernel store actual printk buffer in fixed
> location, thus it is very robust. It was rejected though in favour of
> solution you eventually implemented.
> 
> Also I would like to extend your driver to dump old contents of the ram
> buffer to kernel log, so one wouldn't worry about erasing in on next
> boot after crash.
> Don't know when I do that though.
> 

ramoops uses a circular buffer of fixed size to store more information.
The number of "dumps" depends on the region size of memory you use.

Regards,

Marco
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