Re: Sending SCSI commands in Mac OS X
Re: Sending SCSI commands in Mac OS X
- Subject: Re: Sending SCSI commands in Mac OS X
- From: Terry Lambert <email@hidden>
- Date: Fri, 04 Sep 2009 10:08:36 -0700
Sorry, my answer on the driver was incorrect. Apparently some of the
documentation on <http://developer.apple.com> is out of date, and the
only supported way to access some of these devices is through a user
client.
I guess the last time I used SCSI tapes on Mac OS X (to read some old
QIC tapes on a Blue and White G3), I had installed your company's ES-
Backup product <http://www.ugsoft.de> to get device shims and forgot
about it!
-- Terry
On Jul 23, 2009, at 7:04 AM, email@hidden wrote:
Am 23.07.2009 um 13:26 schrieb Terry Lambert:
Did you go to <http://developer.apple.com> and read the document
"SCSI Architecture Model Device Interface Guide"?
It states:
"By design, Mac OS X does not allow applications to send SCSI or
ATA commands to storage devices unless the application developer
also provides an in-kernel device driver that supports the commands."
One of the intents if this is to allow the driver to model state
for such coomands such that the state if the device is known to the
driver at all times.
For standard tape devices, you should not need to write your own
driver; if you plug the device in, it will show up in /dev,
Never seen a tape drive, neither SCSI, FireWire, USB nor
FibreChannel connected to Mac OS X 10.2 up to 10.5 which shows up
in /dev. What device filename should I look for?
and you can at least issue reads, writes, and standard commands,
such as causing a rewind, via the device file. For non-standard
commands, such as you would use to control loading and unloading
tapes in a tape robot, etc., you will need to write an in-kernel
driver that knows how to talk to the hardware and subclasses the
more generic device (i.e. the IOKit model lets you write only the
missing pieces implementing the missing control commands; you don't
write a whole driver that implements read/write/etc.).
Instead we use SCSITaskDeviceInterface functions from userland as
described in Apple's SCSI Architecture Model Device Interface Guide
"WorkingWithSAM.pdf" in order to implement a "SCSI pass-thru"
functionality. No additional driver required.
Uwe
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