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Re: kernel update




----- Original Message -----
From: "Pieter Grimmerink" <mailinglists@xxxxxxx.nl>
To: <u9900545@xxxxxxx.com>
Sent: den 19 oktober 2002 12:02
Subject: RE: kernel update


>
>
> > -----Original Message-----
> > From: owner-dev-etrax@xxxxxxx.com]On">mailto:owner-dev-etrax@xxxxxxx.com]On
> > Behalf Of u9900545@xxxxxxx.fi
> > Sent: zaterdag 19 oktober 2002 13:46
> > To: dev-etrax@xxxxxxx.com
> > Subject: kernel update
>
> > I'm supposed to write an application which transfers scientific
> > measurement data over ethernet in real time.
> ...
> > 1. Do I need to update the kernel in ETRAX-chip in order to design real
> > time applications or is the standard kernel adequate?
>
> Depends on which parts of the system you want to be realtime.
> For example, you can't expect to receive the measurements realtime
> over ethernet, no matter what you try.
> So what I might do is try to get the measurements timestamped as soon
> as possible, before processing / forwarding them.
> I think in that case, writing a kerneldriver that assigns a timestamp
> to each measurement as soon as it comes in might be allright, even with
> the standard kernel.

What kind of latency/response times are you aiming at?

> > 2. Is it even possible to update the kernel by my self?
> Sure, you find it in the os/linux path under your devboard_lx.
> (supposed you took all the necessary steps to build your development
> environment, like explained in the howtos)
> Type 'make menuconfig' (in os/linux) to have a look at the current kernel
> config.
>
> > I also want to know that can I update the web page in chip somehow? I
> > tried it once, but chip responded that the filesystem is read-only type.
>
> Most parts of the filesystem are readonly (compressed image, loaded from
> flash into ram at bootup),

This is not entirely correct when using the 2.4 kernel and devboard_lx.
In that case the major part of the filesystem is a readonly cramfs image
in flash - pages/files are decompressed to RAM only when they are needed.
(In the old 2.0 NO_MMU (elinux) the entire filesystem was a
 compressed romfs image that was uncompressed to RAM)

You can add files to readonly partition e.g. /usr/html/ and rebuild the
firmware image and upgrade.

> but the remaining free space of the flash is
> mounted on /mnt/flash

I believe there should be a link called /usr/html/local going
to /etc/httpd/html where you could upload your webpages if you don't
want to put the webpages in the readonly partition and upgrade the
whole image.

/Johan