Date: Sun, 01 Jul 2007 22:19:11 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: nate@root.org Cc: marck@rinet.ru, current@freebsd.org Subject: Re: GEOM weirdness with SD flash reader? Message-ID: <20070701.221911.1394573729.imp@bsdimp.com> In-Reply-To: <4688791D.6050007@root.org> References: <46880F1C.3020602@root.org> <20070701.215557.1373430453.imp@bsdimp.com> <4688791D.6050007@root.org>
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In message: <4688791D.6050007@root.org>
Nate Lawson <nate@root.org> writes:
: M. Warner Losh wrote:
: > In message: <46880F1C.3020602@root.org>
: > Nate Lawson <nate@root.org> writes:
: > : Yes, you're exactly right. However, shouldn't a read from a device
: > : trigger a re-taste if the media is removable?
: >
: > I don't think it does. The driver is expected to poll, however...
: >
: > : So the fdisk of da2
: > : should have caused it to re-read the MBR and create /dev/da2s1. I think
: > : maybe there should be a flag set for devices with removable media that
: > : causes the device to be re-tasted on every mount request.
: >
: > Is there even a removable flag to disks?
:
: In SCSI there is, removable flag combined with medium not present:
:
: da2 at umass-sim1 bus 1 target 0 lun 2
: da2: <Generic STORAGE DEVICE 0001> Removable Direct Access SCSI-0 device
: ^^^^^^^^^
: da2: 40.000MB/s transfers
: da2: Attempt to query device size failed: NOT READY, Medium not present
I think you've misunderstood my point. I know that SCSI has this
flag, but I can't find anything in GEOM that it would map to. It
seems a common enough situation that having such a flag in GEOM would
be beneficial and easy to implement.
: What if we kicked off a thread to run every 3 seconds that did a quick
: poll of such devices and sent a devd notify if they arrived (i.e. medium
: present)? It wouldn't work for floppy drives, but we could make this
: part of the da driver or something in usermode like devd itself calling
: camcontrol?
In the past, people have said that polling messes up multimedia
access, so it hasn't happened.
But wouldn't a simple daemon in userland do the same thing? Or
parsing the output of camcontrol inquiry? Camcontrol rescan is a nop
for these devices.
Warner
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