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#1 2004-02-26 21:27:50

Shemeta
Member
Registered: 2004-02-11
Posts: 117

External USB CDRW

Hi guys,

i have an external USB cd burner. when i run cdrecord -scnabus i get the following message:

Cdrecord 2.00.3 (i686-pc-linux-gnu) Copyright (C) 1995-2002 J￿rg Schilling
cdrecord: No such file or directory. Cannot open '/dev/pg*'. Cannot open SCSI driver.
cdrecord: For possible targets try 'cdrecord -scanbus'. Make sure you are root.
cdrecord: For possible transport specifiers try 'cdrecord dev=help'

after running modprobe usb-storage , the cd burner showed up under /dev/cdroms/cdrom1
now i can mount it & read CD's & stuff, but i can't burn CD's.

any help would be appreciated.

Regards Shemeta!

P.S. i am using 2.6.3-scsi.

P.P.S. i forgot to mention that the burner is HP-8200.

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#2 2004-02-26 21:37:42

wakeupbomb
Member
From: Liverpool, UK
Registered: 2004-02-15
Posts: 164

Re: External USB CDRW

Have you tried using k3b or xcdroast to burn a cd? Because cdrecord -scanbus gives me the same message as what you get, but i can burn cds fine. I believe cdrecord needs to be sent some commands to pick up the cd writer, /dev/ something or other. I can't remember right now. I'll have a look.

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#3 2004-02-26 21:41:01

wakeupbomb
Member
From: Liverpool, UK
Registered: 2004-02-15
Posts: 164

Re: External USB CDRW

try this as root and see if anything comes up

cdrecord dev=scsibus -scanbus

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#4 2004-02-26 22:44:36

Shemeta
Member
Registered: 2004-02-11
Posts: 117

Re: External USB CDRW

i still get the same error!  sad

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#5 2004-02-26 23:44:22

wakeupbomb
Member
From: Liverpool, UK
Registered: 2004-02-15
Posts: 164

Re: External USB CDRW

so k3b or xcdroast doesn't detect the drive?

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#6 2004-02-26 23:46:44

Shemeta
Member
Registered: 2004-02-11
Posts: 117

Re: External USB CDRW

xcdroast detects it only when i run modprobe usb-storage. but i am not sure if that works to burn CDs.

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#7 2004-02-26 23:54:54

wakeupbomb
Member
From: Liverpool, UK
Registered: 2004-02-15
Posts: 164

Re: External USB CDRW

Hmm ok
What device is your cd writer linked to? In kde info center under storage devices it tells me mine is /dev/cdroms/cdrom0
and if i type as root
cdrecord =/dev/cdroms/cdrom0 -scanbus
it detects my writer

*edit* ah i see you already know what the device is
cdrecord =/dev/cdroms/cdrom1 -scanbus

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#8 2004-02-27 01:31:31

Xentac
Forum Fellow
From: Victoria, BC
Registered: 2003-01-17
Posts: 1,797
Website

Re: External USB CDRW

You need the sg module.


I have discovered that all of mans unhappiness derives from only one source, not being able to sit quietly in a room
- Blaise Pascal

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#9 2004-02-27 15:20:44

rls
Member
From: contracosta, california
Registered: 2003-08-20
Posts: 60

Re: External USB CDRW

For my uplift and edification, why is the module sg needed for a USB device in these days and times? Why don't usbfs and libusb handle the situation?


"Es gibt nichts mehr praktish als theorie" L. Boltzmann

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#10 2004-02-27 16:01:35

Xentac
Forum Fellow
From: Victoria, BC
Registered: 2003-01-17
Posts: 1,797
Website

Re: External USB CDRW

Because, by specification, all usb hard drives are scsi devices.  Just like all cd burners, that use ATAPI, are scsi devices.


I have discovered that all of mans unhappiness derives from only one source, not being able to sit quietly in a room
- Blaise Pascal

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#11 2004-02-27 17:57:04

dp
Member
From: Zürich, Switzerland
Registered: 2003-05-27
Posts: 3,363
Website

Re: External USB CDRW

Xentac wrote:

Because, by specification, all usb hard drives are scsi devices.  Just like all cd burners, that use ATAPI, are scsi devices.

what about not using ide-scsi? then they are atapi-native?


The impossible missions are the only ones which succeed.

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#12 2004-02-27 23:10:52

rls
Member
From: contracosta, california
Registered: 2003-08-20
Posts: 60

Re: External USB CDRW

I guess that I understand Xentac's answer. USB is a type of bus and SCSI is a type of interface for devices. The sg module is needed to handle the interface hardware in the external hard drive. The USB services (uhci/ohci/ehci, usbstorage,...) handle the USB hardware.

But, another question arises. My laptop has a cd reader/burner which is, according to Xentac, a SCSI device. sg is neither compiled-in to my 2.6.3 kernel nor in my MODULES () in rc.conf. Yet cdrecord recognizes it with dev=ATAPI:0,0,0. Is there software in or activated by cdrecord that performs the function of sg? Is there a difference because my cd reader/burner is on a PCI bus and not a USB bus?


"Es gibt nichts mehr praktish als theorie" L. Boltzmann

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#13 2004-02-28 09:45:42

sarah31
Member
From: Middle of Canada
Registered: 2002-08-20
Posts: 2,975
Website

Re: External USB CDRW

i believe the latter question is the case. usb and ide devices are treated very differently (which is logical since they are different technology). Xantac may have a more thorough answer for you though.


AKA uknowme

I am not your friend

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#14 2004-02-28 10:58:10

Xentac
Forum Fellow
From: Victoria, BC
Registered: 2003-01-17
Posts: 1,797
Website

Re: External USB CDRW

IIRC, sg is for generic scsi devices.  A scsi drive is specific, thus sd_mod is what you need for your cd drive.

Reading your question again.  ATAPI, while being a scsi protocol, is over an ide interface.  cdrecord has the drivers (that's why you specify ATAPI:) to handle scsi protocol data over an ide device instead of the kernel having to do it.  This is the purer way of handling it (why should the kernel need to speak scsi to a device that knows ide perferctly well and only needs to speak scsi when writing?).

Look at all of this, "according to Xentac", "Xentac says", and, "In accordance with the prophecy"... it's like I'm a god or something.


I have discovered that all of mans unhappiness derives from only one source, not being able to sit quietly in a room
- Blaise Pascal

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#15 2004-02-28 15:30:24

rls
Member
From: contracosta, california
Registered: 2003-08-20
Posts: 60

Re: External USB CDRW

About Xentac being a god I don't know, more like the Oracle of Delphi. The answers are always interesting, if sometimes cryptic. In any case many thanks for your time and expert(ea)se.

This thread started with an external USB cd burner. One post implied the sg module was required, another the sd_mod module. What am I missing?

So we have buses, interfaces, devices, and protocols (not to mention controllers and bridges). A confusing zoo. No wonder the time efficient method is to put all the services into the kernel or compile as modules until one has a clear understanding.

SCSI and USB: SCSI would seem to be an interface, so there can be SCSI devices. USB would seem to be a bus so there are no USB devices persae, only devices that reside on a USB bus.

The fact that SCSI devices can be daisy chained doesn't seem to make SCSI a bus as well as an interface.

And what about serial ports, parallel ports, PS/2 ports? Since there are serial, parallel and PS/2 devices, they would seem to be interfaces. But one doesn't speak of a parallel port bus etc., so they must connect "directly", somehow, to the system.

It would seem every device must have an interface to understand a protocol which is a signal specification. Some devices reside on buses, other connect "directly." Thus the complete specification of every device must include the interface and may need to include the bus. And services, either complied-in the kernel or as modules, are necessary for the interface and for the bus if present.


"Es gibt nichts mehr praktish als theorie" L. Boltzmann

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#16 2004-03-03 18:31:07

terrapin
Member
From: Lockport, IL
Registered: 2003-08-06
Posts: 104

Re: External USB CDRW

Another very important thing to check is whether cdrecord supports the cdrw drive you are attempting to use.  I found this out the hard way recently as mine ws not supported.  sad

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