FreeBSD 8.2-PRERELASE doesn't see slice on SDHC card in ?cardreader ?-- what should I do?

Oliver Fromme olli at lurza.secnetix.de
Tue Dec 21 11:26:42 UTC 2010


Lev Serebryakov <lev at serebryakov.spb.ru> wrote:
 >   It  works!  But  it  is  not intiutive at all :)

The command opens the device for writing (but it doesn't
actually write anything), and closes it immediately.
This causes the GEOM system to read and "taste" the
device and look for new slices or partitions.

 >   Why all CAM-related commands like "load" and "open" don't work

All of those commands are only related to the hardware,
i.e. SCSI busses and devices.  They are not related to
the _content_ of the device (slices etc.).
In other words, the problem is on a different level.

 >   (I don't mention auto-sensing  ;-))?  Is it problem with my
 >   cardreader or common problem for FreeBSD?

As Andriy wrote, it's kind of both.

The main problem here is that there is no notification
mechanism when you insert an SD card (the same is true
for floppy disks and CD drives, by the way, but it's less
of a problem because they usually don't have slices).
So, FreeBSD does not know when a new card is inserted,
so the GEOM system does not know when to re-read the
slice table from the device.

However, there is a notification for USB devices.  So,
if your card reader is an external USB device, you can
remove it and then plug it back (with the SD card already
inserted!).  The USB notification mechanism will tell
GEOM that there is a new device, and GEOM will read it
and find the slices.  Of course, this is not possible if
the card reader is built-in (e.g. in a notebook), so you
have to use the work-around by opening the device for
writing.

It's not trivial to fix the problem in a clean way.

Best regards
   Oliver

-- 
Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M.
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