>From [EMAIL PROTECTED] Thu Feb 11 07:19:14 1999
>>>I would welcome even this overall, but I disagree with the device
>>>addressing scheme of SCG and CAM. It introduces an artificial
>>>dichotomy between the specialized and generic interfaces, resulting in
>>>more complex application code (or more likely, lazy application code
>>>that dumps the responsibility for matching up devices onto the user).
>>>/dev/sg devices should exist only as placeholders, not a primary
>>>access mechanism.
>>
>>I disagree with anything else. Your suggestion introduces this artifical
>>difference between the SCSI devices and the UNIX device I would have to open.
>This depends on the point of view. /dev/sr0 is not opened and then
>explicitly attached to a B:T:L; who is introducing the dichotomy is up
>for argument. I will submit, also, that B:T:L is a foreign concept in
>ATAPI, something which is very much within the realm we're concerning
>ourselves with here. For ATAPI and parport SCSI, we have to assign
>the device illusory numbers.
That's not true:
- The SCSI bus numbering is up to the kernel software.
- ATAPI is SCSI over IDE. Luns a handled the samw way as they
ar in old 8-bit/PP SCSI
- It is obvious to assign targets 0 and 1 to master and slave
as the SCSI target is derived from a HW protocol that
selects the targets. On a different transport hardware
(SCSI-3 introduces different HW transport layers e.g. fiber SCSI)
you need target numbers that fit fot that transport.
>>>All this hunting and error prone device mapping isn't necessary if one
>>>lets go of elevating SCSI over the design idiom of the native OS.
>>
>>This error prone device mapping is only needed on Linux because the
>>kernel SCSI modules are using the wrong addressing methods.
>I fully agree that the implementation of Linux further complicates the
>matter, moreso than the worst SCG would.
I am planning to enhance the scg driver to provide additional device nodes
for each target/lun. This would allow to modify the permissions separately
as you can do on IRIX or HP-UX.
>>But it is called *.fkus.gmd.de because the internet community decided
>>to use this addressing method. To address my computer I need to know
>>the IPaddress and I know it because I did set it up.
>Even IP sets up an abstraction over the raw numbers, because the
>numbers are not suitable for everyday use by humans. Note that DHCP
>obsoletes even knowing the IP quartet during setup.
But this abstraction is _neither_ part of the IP stack in the kernel _nor_
part of the library functions that open IP connections or send IP data
over the network. A separate mapping mechanism is used to make IP numbers
user friendly.
Note that SCSI in fact is a protocol like TCP/IP so the mapping that is required
to make the system more easy to use, should be added in a similar way
to TCP/IP. Cdrecord provides such a mapping machanism since about two months
although I planned to do this for a long time. And important:
It does it in the UNIX way by reading the file /etc/default/cdrecord
You are free to look at it and to write software that will help the
novice user to create a file /etc/default/cdrecord that meets his own
needs.
J�rg
EMail:[EMAIL PROTECTED] (home) J�rg Schilling D-13353 Berlin
[EMAIL PROTECTED] (uni) If you don't have iso-8859-1
[EMAIL PROTECTED] (work) chars I am J"org Schilling
URL: http://www.fokus.gmd.de/usr/schilling ftp://ftp.fokus.gmd.de/pub/unix
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