SCSI Emulation w/ DMA

SCSI Emulation w/ DMA

[David Yeu]

Hi everyone,

I have SCSI emulation on my CDR drive in order to burn and the like,
but I was confused by the following entries in /var/log/messages...

----------------------------------------------------------------------
Aug  5 12:18:48 localhost kernel: SCSI subsystem driver Revision: 1.00
Aug  5 12:18:19 localhost rc.sysinit: Setting clock  (localtime): Mon
Aug  5 12:18:13 UTC 2002 succeeded
Aug  5 12:18:49 localhost kernel: scsi0 : SCSI host adapter emulation
for IDE ATAPI devices
Aug  5 12:18:19 localhost rc.sysinit: Loading default keymap succeeded
Aug  5 12:18:49 localhost kernel:   Vendor: LITE-ON   Model: LTR-24102B
         Rev: 5S0J
Aug  5 12:18:19 localhost rc.sysinit: Setting default font (lat0-sun16):
   succeeded
Aug  5 12:18:49 localhost kernel:   Type:   CD-ROM        ANSI SCSI
revision: 02
Aug  5 12:18:19 localhost rc.sysinit: Activating swap partitions:  succeeded
Aug  5 12:18:49 localhost kernel: hdc: DMA disabled
-----------------------------------------------------------------------

The last line says that DMA is disabled, but it refers to hdc.  Since
my /dev/cdrom is linked to /dev/scd0, and /dev/cdrecorder is linked
to /dev/sg0, does that mean DMA is working anyhow?  How can I tell?

(I was prompted into peeking around after burning seemed a little
slow..)

Thanks in advance,
Dave.


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Re: SCSI Emulation w/ DMA

[Ray Olszewski]

Even though you have scsi emulation enabled, there is an ide driver hidden 
in the demimonde of your system that the scsi emulator communicates 
through. It is the ide driver, the part that actually talks to the 
hardware, that either has DMA on or off.

Almost surely, the message you are seeing means that DMA is off. To check 
it, run "hdparm /dev/hdc" and see that the resulting report says about DMA. 
If you want to turn it on, run (as root) "hdparm -d 1 /dev/hdc". If you 
always want it on, add that line to one of the system's  init scripts 
(probably whatever corresponds to rclocal on your system).

Now I am not at all sure about this next part ... but I doubt that the DMA 
setting is what is making your CD burns slow. How are you burning (what is 
the actual command-line string you send)? What speed is your drive? How 
long is it taking to burn (your "a little slow" could be someone else's 
"fast")? What are you burning (iso images? copies of music CDs? VCDs?)

At 04:57 PM 8/19/02 -0500, David Yeu wrote:
>Hi everyone,
>
>I have SCSI emulation on my CDR drive in order to burn and the like,
>but I was confused by the following entries in /var/log/messages...
>
>----------------------------------------------------------------------
>Aug  5 12:18:48 localhost kernel: SCSI subsystem driver Revision: 1.00
>Aug  5 12:18:19 localhost rc.sysinit: Setting clock  (localtime): Mon
>Aug  5 12:18:13 UTC 2002 succeeded
>Aug  5 12:18:49 localhost kernel: scsi0 : SCSI host adapter emulation
>for IDE ATAPI devices
>Aug  5 12:18:19 localhost rc.sysinit: Loading default keymap succeeded
>Aug  5 12:18:49 localhost kernel:   Vendor: LITE-ON   Model: LTR-24102B
>         Rev: 5S0J
>Aug  5 12:18:19 localhost rc.sysinit: Setting default font (lat0-sun16):
>   succeeded
>Aug  5 12:18:49 localhost kernel:   Type:   CD-ROM        ANSI SCSI
>revision: 02
>Aug  5 12:18:19 localhost rc.sysinit: Activating swap partitions:  succeeded
>Aug  5 12:18:49 localhost kernel: hdc: DMA disabled
>-----------------------------------------------------------------------
>
>The last line says that DMA is disabled, but it refers to hdc.  Since
>my /dev/cdrom is linked to /dev/scd0, and /dev/cdrecorder is linked
>to /dev/sg0, does that mean DMA is working anyhow?  How can I tell?
>
>(I was prompted into peeking around after burning seemed a little
>slow..)




--
-------------------------------------------"Never tell me the odds!"--------
Ray Olszewski					-- Han Solo
Palo Alto, California, USA			  ray@comarre.com
-------------------------------------------------------------------------------

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starting X with different XF86Configs

[James & Tatiana Miller]

Hello all:

I've got a notebook that I will be hooking an external display to from 
time to time. Of course the external display has totally different 
settings than the notebook's native display (native display is limited to 
800x600 res, for example). For this reason, I'd like to be able to start X 
with one of 2 differing XF86Config files, depending on whether I'll be 
using the notebook's own monitor or the external one. I've got 
working XF86Config files for both the external and native displays. 
What I'm having some trouble with is figuring out how to invoke one or the 
other XF86Config file when I start X. Any suggestions on how to go about 
this?

Thanks, James

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Re: starting X with different XF86Configs

[Ray Olszewski]

At 06:36 PM 8/19/02 -0500, James & Tatiana Miller wrote:
>Hello all:
>
>I've got a notebook that I will be hooking an external display to from
>time to time. Of course the external display has totally different
>settings than the notebook's native display (native display is limited to
>800x600 res, for example). For this reason, I'd like to be able to start X
>with one of 2 differing XF86Config files, depending on whether I'll be
>using the notebook's own monitor or the external one. I've got
>working XF86Config files for both the external and native displays.
>What I'm having some trouble with is figuring out how to invoke one or the
>other XF86Config file when I start X. Any suggestions on how to go about
>this?

Never needed to do this myself, but the man page for "XF86Config" says you 
can specify an alternate file with the "-xf86config" argument on the 
command line. The man page is a bit unclear as to what command it 
associates this aggument with, and you don't say how you are starting X 
anyway ... but I'd *try* passing it as a server argument to startx ("startx 
-- -xf86config appropriate_file_name") and seeing it that did the trick.

If that's not quite it, perhaps this is enough of a start that you can use 
the man system to track down the right way to pass this argument yourself.


--
-------------------------------------------"Never tell me the odds!"--------
Ray Olszewski					-- Han Solo
Palo Alto, California, USA			  ray@comarre.com
-------------------------------------------------------------------------------

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Re: starting X with different XF86Configs

[Matthias Schweinoch]

don't know if this is considered a "bad approach", but another way to do
this is to simply name your working XF86Config files appropriately and then
just create a symlink to whichever file it is your using.

matthias

> >What I'm having some trouble with is figuring out how to invoke one or
the
> >other XF86Config file when I start X. Any suggestions on how to go about
> >this?
>
> If that's not quite it, perhaps this is enough of a start that you can use
> the man system to track down the right way to pass this argument yourself.


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Re: starting X with different XF86Configs

[James & Tatiana Miller]

On Tue, 20 Aug 2002, Matthias Schweinoch wrote:

> don't know if this is considered a "bad approach", but another way to do
> this is to simply name your working XF86Config files appropriately and then
> just create a symlink to whichever file it is your using.
> 
Hmmm. This I don't understand. What would be the purpose of symlinking, 
and from where (i.e., what point in the Linux startup process) would the 
symlink get used? Are you talking about creating a symlink pointing to the 
desired XF86Config and calling it "XF86Config" each time I am preparing to 
start X? I can see how that would work, but it seems about the same amount of 
time and trouble as renaming XF86Configs each time I wish to start X. I 
guess I'm looking for a more elegant and less time-consuming solution. So 
far, Ray's looks best.

Thanks, James 

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Re: starting X with different XF86Configs

[pa3gcu]

On Tuesday 20 August 2002 15:39, James & Tatiana Miller wrote:
> On Tue, 20 Aug 2002, Matthias Schweinoch wrote:
> > don't know if this is considered a "bad approach", but another way to do
> > this is to simply name your working XF86Config files appropriately and
> > then just create a symlink to whichever file it is your using.
>
> Hmmm. This I don't understand. What would be the purpose of symlinking,
> and from where (i.e., what point in the Linux startup process) would the
> symlink get used? Are you talking about creating a symlink pointing to the
> desired XF86Config and calling it "XF86Config" each time I am preparing to
> start X? I can see how that would work, but it seems about the same amount
> of time and trouble as renaming XF86Configs each time I wish to start X. I
> guess I'm looking for a more elegant and less time-consuming solution. So
> far, Ray's looks best.
>
> Thanks, James


Use your imaganation, create a script, call it what you want, i will call it 
GoX

#!/bin/sh

case "$1" in

  1) 
	/bin/ln -s /etc/X11/XF86Config-1 /etc/X11/XF86Config
	/usr/X11R6/bin/startx
	;;
  2)
	/bin/ln -s /etc/X11/XF86Config-2 /etc/X11/XF86Config
	/usr/X11R6/bin/startx
	;;
  *)
	/bin/echo "USAGE: GoX 1 or GoX 2 "
esac

#------------------------------

No use the command;
'chmod a+x GoX'
To make it executable.

Its all so easy...

-- 
Regards Richard
pa3gcu@zeelandnet.nl
http://people.zeelandnet.nl/pa3gcu/

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Re: starting X with different XF86Configs

[James & Tatiana Miller]

On Mon, 19 Aug 2002, Ray Olszewski wrote:
> you don't say how you are starting X anyway ...

Ray:

Thanks for your answer. I'm starting X from the cli - "startx". Is there 
some other way it could be started, offering a choice of XF86Configs?

James

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Re: starting X with different XF86Configs

[Ray Olszewski]

At 10:30 AM 8/20/02 -0500, James & Tatiana Miller wrote:
>On Mon, 19 Aug 2002, Ray Olszewski wrote:
> > you don't say how you are starting X anyway ...
>
>Ray:
>
>Thanks for your answer. I'm starting X from the cli - "startx". Is there
>some other way it could be started, offering a choice of XF86Configs?


Not that I know of. I already suggested a cli method of selecting the 
config file when running X via startx, and someone sles suggested the 
alternative of using symlinks and changing the symlink depending on what 
display you are using. I suppose you could write a wrapper program for 
startx (or even modify startx to do this; startx is just a bash script that 
calls xinit) that asked you what file you wanted to use, then passed on the 
appropriate command-line argument.

I was mainly trying to make sure you were not starting X with xdm. I don't 
know how one would pass command-line arguments with xdm, since there is no 
command line in that case.


--
-------------------------------------------"Never tell me the odds!"--------
Ray Olszewski					-- Han Solo
Palo Alto, California, USA			  ray@comarre.com
-------------------------------------------------------------------------------

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Re: SCSI Emulation w/ DMA

[David Yeu]

Thanks for the help Ray...

To answer your questions:
I'm using a Plextor 24X with the command, 'cdrdao write toc.file',
and I'm burning a mix of isos and music cds.
Under Windows, this process never seemed to take more than three
and a half minutes, but with Linux, average burn times hover around
four and change.  Now I know, thirty seconds isn't much to whine over,
but I was just curious to see if it was something I had failed to do.
I read both the CD-ROM HOW-TO, and the CD-Writing HOW-TO, but I must
have missed the illuminating section.

More interestingly, the burner I have at work is a generic Lite-On
24/10/40, and it usually takes anywhere from 8-10 minutes to burn
a cd, under both Windows and Linux.  I never gave it much thought,
however, because hey I'm at work, and I might as well take the
opportunity to grab a coffee and a cigarette.

Dave.


Ray Olszewski wrote:
> Even though you have scsi emulation enabled, there is an ide driver 
> hidden in the demimonde of your system that the scsi emulator 
> communicates through. It is the ide driver, the part that actually talks 
> to the hardware, that either has DMA on or off.
> 
> Almost surely, the message you are seeing means that DMA is off. To 
> check it, run "hdparm /dev/hdc" and see that the resulting report says 
> about DMA. If you want to turn it on, run (as root) "hdparm -d 1 
> /dev/hdc". If you always want it on, add that line to one of the 
> system's  init scripts (probably whatever corresponds to rclocal on your 
> system).
> 
> Now I am not at all sure about this next part ... but I doubt that the 
> DMA setting is what is making your CD burns slow. How are you burning 
> (what is the actual command-line string you send)? What speed is your 
> drive? How long is it taking to burn (your "a little slow" could be 
> someone else's "fast")? What are you burning (iso images? copies of 
> music CDs? VCDs?)
> 
> At 04:57 PM 8/19/02 -0500, David Yeu wrote:
> 
>> Hi everyone,
>>
>> I have SCSI emulation on my CDR drive in order to burn and the like,
>> but I was confused by the following entries in /var/log/messages...
>>
>> ----------------------------------------------------------------------
>> Aug  5 12:18:48 localhost kernel: SCSI subsystem driver Revision: 1.00
>> Aug  5 12:18:19 localhost rc.sysinit: Setting clock  (localtime): Mon
>> Aug  5 12:18:13 UTC 2002 succeeded
>> Aug  5 12:18:49 localhost kernel: scsi0 : SCSI host adapter emulation
>> for IDE ATAPI devices
>> Aug  5 12:18:19 localhost rc.sysinit: Loading default keymap succeeded
>> Aug  5 12:18:49 localhost kernel:   Vendor: LITE-ON   Model: LTR-24102B
>>         Rev: 5S0J
>> Aug  5 12:18:19 localhost rc.sysinit: Setting default font (lat0-sun16):
>>   succeeded
>> Aug  5 12:18:49 localhost kernel:   Type:   CD-ROM        ANSI SCSI
>> revision: 02
>> Aug  5 12:18:19 localhost rc.sysinit: Activating swap partitions:  
>> succeeded
>> Aug  5 12:18:49 localhost kernel: hdc: DMA disabled
>> -----------------------------------------------------------------------
>>
>> The last line says that DMA is disabled, but it refers to hdc.  Since
>> my /dev/cdrom is linked to /dev/scd0, and /dev/cdrecorder is linked
>> to /dev/sg0, does that mean DMA is working anyhow?  How can I tell?
>>
>> (I was prompted into peeking around after burning seemed a little
>> slow..)



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Re: SCSI Emulation w/ DMA

[Ray Olszewski]

At 09:22 AM 8/20/02 -0500, David Yeu wrote:
>Thanks for the help Ray...
>
>To answer your questions:
>I'm using a Plextor 24X with the command, 'cdrdao write toc.file',
>and I'm burning a mix of isos and music cds.
>Under Windows, this process never seemed to take more than three
>and a half minutes, but with Linux, average burn times hover around
>four and change.  Now I know, thirty seconds isn't much to whine over,
>but I was just curious to see if it was something I had failed to do.
>I read both the CD-ROM HOW-TO, and the CD-Writing HOW-TO, but I must
>have missed the illuminating section.

I'm not sure what would qualify here as "illuminating". I don't use cdrdao 
myself (I use cdrecord), but in my CD burnings, I notice two things that 
might be relevant:

1. cdrecord waits about 10 seconds before it starts burning, with a 
countdown on the screen, to give me an option to abort the burn.

2. I too have a 24x burner (a Sony), and I tell this to cdrecord. 
Nonetheless, it always tells me that it is burning (iso images) at 12x, not 
24x.

Since the discrepancies you are seeing between Windows and Linux are so 
small, they are probably the result of some subtlety in the way the two 
apps work (possibly including what each does before and after you start the 
clock -- with differences that small, asking how exact your timings are is 
a reasonable thing to do). I mentioned those two not to diagnose your 
situation, but as examples of the kinds of things that might be going on. 
either in your home setting or in the work one you describe below.


>More interestingly, the burner I have at work is a generic Lite-On
>24/10/40, and it usually takes anywhere from 8-10 minutes to burn
>a cd, under both Windows and Linux.

[rest deleted]

--
-------------------------------------------"Never tell me the odds!"--------
Ray Olszewski					-- Han Solo
Palo Alto, California, USA			  ray@comarre.com
-------------------------------------------------------------------------------

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