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Re: need help with CompactFlash/PCMCIA

To: linux-mips@linux-mips.org
Subject: Re: need help with CompactFlash/PCMCIA
From: Ulrich Eckhardt <eckhardt@satorlaser.com>
Date: Wed, 16 Mar 2005 08:16:52 +0100
In-reply-to: <4237CCDC.1030104@embeddedalley.com>
Organization: Sator Laser GmbH
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <200503151245.15920.eckhardt@satorlaser.com> <200503160651.42705.eckhardt@satorlaser.com> <4237CCDC.1030104@embeddedalley.com>
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Pete Popov wrote:
> Ulrich Eckhardt wrote:
> > Hmmm, I just had a scary thought: I don't have any userspace programs
> > running yet, meaning also no cardmgr, because I intend to boot from that
> > CF card - is that possible at all? FYI, I don't need any hotplugging at
> > all.
>
> Do you really mean "boot" from it or "root" from it? If you want to "boot"
> from it, you need to work on your boot loader to be able to fetch the
> kernel from CF. 

I have two MiB of flash on board, which contains the bootloader (YAMON) and 
some free space for a kernel. This is used to boot from. IOW, I mean to root 
from the CF card, not to boot from it.

> If you mean "root" from it, then you are approaching this 
> the wrong way -- it won't work through the pcmcia stack and cardmgr because
> that means you already have a root fs up and mounted. You could do this by
> creating a small ramdisk to serve as the root fs, run a special script on
> startup that loads the driver, starts cardmgr, cardmgr then detects the
> card and loads ide-cs.o, and finally the script exits back to the kernel.
> At that point the kernel mounts the real rootfs which is on the card
> itself.

Sounds like the way to go.

> Or, you use the ide mode/feature of CF and get it to work that way, but
> I've never had to do that myself. Then the card looks like an ide device.
> That's something one of our guys at Embedded Alley has done in the past.
> Don't know how easy it is; I'll ping him.

Sounds like another way to go, in particular since I don't need hotplugging 
and other PCMCIA features (and their overhead).

Pete, I owe you a beer. I can see a few things much, much clearer now, thanks!

Uli

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