[haiku-bugs] Re: [Haiku] #9655: External usb hard disk with switch doesn't work/mount properly
- From: "mmlr" <trac@xxxxxxxxxxxx>
- Date: Sat, 13 Apr 2013 14:56:21 -0000
#9655: External usb hard disk with switch doesn't work/mount properly
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Reporter: Giova84 | Owner: mmlr
Type: bug | Status: new
Priority: normal | Milestone: R1
Component: | Version: R1/Development
Drivers/USB | Keywords: External usb hard disk with switch
Resolution: | doesn't work properly spindown mount
Blocked By: | Blocking:
Has a Patch: 0 | Platform: x86
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Comment (by mmlr):
There's really no mystery as to the power button here. The usb_disk driver
is a really simple driver that supports a subset of SCSI, just enough to
get most USB mass storage devices going. It is not a SCSI module and does
not share code with the SCSI layer. It eventually needs to be rewritten to
be such a module, but for this to happen the USB stack itself has to be
brought to the new device API. Noone has done that work yet, as it's kind
of non trivial.
In any case, usb_disk does not support spin up/down. It does not attempt
to power the disk on when a new device is attached. It assumes that when a
device is connected and enumerating a LUN, the backing device is powered
already. This assumption holds for pretty much every USB stick and most
card readers or similar devices. It usually holds for external USB disks
as well, but breaks in the case of your device.
The delay you mention in bringing the device back up once it has spun down
comes from the same limitation. The usb_disk driver does not recognise the
fact that the disk is not powered anymore and does not take action to
bring it back up. Instead it simply sees this case as a generic error and
initiates a normal mass storage reset. In the case of your device it seems
like that also powers the disk back on (this is implementation dependent).
The reset procedure does however take a lot longer than a simple spin up
would, that's where the delay you see comes from.
I don't have an explanation for the "unmount on opening a zip file"
problem, it is probably unrelated to usb_disk. The behaviour you describe
sounds more like a filesystem problem causing the volume to be uncleanly
unmounted on an error. Re-opening a file from that disk could then cause
the volume to be auto mounted again. If it was a usb_disk error that
caused the device to vanish, there would be no volume to be mounted
anymore. Please provide a syslog snippet so this can be verified and
possibly open a new ticket if it clearly is a filesystem error.
--
Ticket URL: <http://dev.haiku-os.org/ticket/9655#comment:11>
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