[haiku-bugs] Re: [Haiku] #6181: USB DVD-RW Drive detected as USB Stick
- From: "mmlr" <trac@xxxxxxxxxxxx>
- Date: Tue, 08 Jan 2013 16:27:06 -0000
#6181: USB DVD-RW Drive detected as USB Stick
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Reporter: streak | Owner: mmlr
Type: bug | Status: new
Priority: normal | Milestone: R1
Component: Drivers/USB | Version: R1/alpha2
Resolution: | Keywords:
Blocked By: | Blocking:
Has a Patch: 0 | Platform: All
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Comment (by mmlr):
Even if they were at a different path, the usb_disk driver only supports a
very limited subset of SCSI. It does not support the CD SCSI commands at
all, so only CD drives that work as plain mass storage devices work with
usb_disk right now. This is intentional, or at least originally was, due
to many devices crashing or hanging when exposed to the full SCSI command
set. I don't know if current devices are any better than the ones at the
time I implemented it, but looking at the quirks list in linux doesn't
inspire confidence.
To get actual generic SCSI support the usb_disk driver needs to be
replaced with a SCSI module that uses the USB mass storage protocol and
can handle the full range of SCSI commands our SCSI layer provides. The
ability to flag different misbehaviours and a long list of quirks will
have to be implemented to limit the commands used with problematic devices
though. Many USB sticks and external drives will otherwise stop working.
Alternatively a white list could be implemented where actually working
devices are added, and only these get exposed to all SCSI commands whereas
the rest is filtered down to the subset currently supported by usb_disk.
This feels a bit backwards however.
--
Ticket URL: <http://dev.haiku-os.org/ticket/6181#comment:5>
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