GEOM weirdness with SD flash reader?

[M. Warner Losh]

In message: <4688791D.6050007 at root.org>
            Nate Lawson <nate at root.org> writes:
: M. Warner Losh wrote:
: > In message: <46880F1C.3020602 at root.org>
: >             Nate Lawson <nate at 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