How to setup DMA on my CD-RW?

[HoytDuff]

On Thursday 09 October 2003 03:16 am, shrek-m at gmx.de wrote:
>
> steps to reproduce:
>
> 1. go to
> http://www.distrowatch.com/
>
> 2. go to redhat  [#1 mandrake #2 redhat]
> http://distrowatch.com/table.php?distribution=redhat
>

Neither step is intuitive. Distrowatch for documentation? 


> 3. here you will find "documentation"
> http://www.redhat.com/docs/
>

This makes enough sense to be step #1.

> 4. search for "dma cdrom sysconfig"
> http://www.redhat.com/apps/search/results.html
>

Requires that you have enough knowledge to associate these three terms.


> 5. here you can find he "Red Hat Linux 9 Red Hat Linux Reference Guide"
> http://www.redhat.com/docs/manuals/linux/RHL-9-Manual/pdf/rhl-rg-en-9.pdf
>

I would expect info on configuring hardware to _not_ be in a reference guide, 
but in the installation guide.

> 6. it will be opened with xpdf, search dma=1
> on page 48 you can find chapter "4.1.10"
>

Again, requires that you already know the answer to your question before you 
ask it.

>
> here you are.
>
> /etc/sysconfig/harddiskhd[a-h]
> USE_DMA=1

Like many things Linux, it's easy once you know the solution. Could you have 
found it had you not already known the answer? Possibly, but it's not as easy 
as you make it out to be.

Here's a more real-world approach:

1. Start by searching http://www.google.com/linux for "How to setup DMA on my 
CD-RW". This assumes that you know enough to use better places to search for 
info. 

2. First page of results provides clue that hdparm may be used to toggle DMA.

3. Read man page of hdparm, find the part that deals with DMA.

3. Manually implement this and verify that it does indeed provide some 
benefit. You must somehow make that leap of understanding to know that 
something related to sysconfig might help without knowing about sysconfig in 
the first place.

4. Try and figure it how to make DMA set to ON  automatically.

Interestingly, if I add "red hat" to the Google query, I found this link on 
page two that appears to answer provide and alternate answer to the question:  
http://www.jeremythompson.uklinux.net/RH8-0/DVD.html

"2. To enable DMA access for the DVD drive (prevents video frame loss and gaps 
in the sound), add the following line to /etc/modules.conf: 

options ide-cd dma=1"

Which, I believe, was in the release notes for Red Hat 8, the version that 
author was addressing. 

But where was that originally documented? In the docs for sysconfig which you 
had to know about before asking the question.

Finding information is all about knowing what questions to ask and knowing 
where to ask them. Because of that, it's not an easy task.

-- 
Hoyt