Content-Type: text/plain; charset=US-ASCII
From: Tim Jansen <tim@tjansen.de>
To: Martin Dalecki <dalecki@evision-ventures.com>
Subject: Re: Device Registry (DevReg) Patch 0.2.0
Date: Tue, 24 Apr 2001 13:44:26 +0200
In-Reply-To: <01042403082000.05529@cookie> <3AE54A24.C90067F6@evision-ventures.com>
In-Reply-To: <3AE54A24.C90067F6@evision-ventures.com>
Cc: linux-kernel@vger.kernel.org
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Sender: linux-kernel-owner@vger.kernel.org

On Tuesday 24 April 2001 11:40, Martin Dalecki wrote:
> Tim Jansen wrote:
> > The Linux Device Registry (devreg) is a kernel patch that adds a device
> > database in XML format to the /proc filesystem. It collects all
> OH SHIT!!      ^^^
> Why don't you just add postscript output to /proc?

XML wasn't my first choice. The 0.1.x versions used simple name/value pairs, 
I gave this up after trying to fit the complex USB 
configuration/interface/endpoint data into name/value pairs. Thinking about 
text file formats that allow me to display hierarchical information,  XML was 
the obvious choice for me. Are there alternatives to get complex and 
extendable information out to user space? (see 
http://www.tjansen.de/devreg/devreg.output.txt for a example /proc/devreg 
output)
My other ideas were:
- using a simple binary format, just dump structs. This would break all 
applications every time somebody changes the format, and this should happen 
very often because of the nature of the format
- using a complicated, extendable binary format, for example chunk-based like 
(a|r)iff file formats. This would add more code in the kernel than XML 
output, is difficult to understand and requires more work in user space 
(because XML parsers are already available)
- making up a new text-based format with properties similar to XML because I 
knew that many people dont like the idea of XML output in the kernel.. I 
really thought about it, but it does not make much sense.

The actual code overhead of XML output compared to a format like 
/proc/bus/usb/devices is almost zero, XML is only a little bit more verbose. 
I agree that XML is not perfect for this kind of data, but it is simple to 
generate, well known and I dont see a better alternative. 

bye..
 
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