usb-storage device wrongly seen as "write protect is on"

usb-storage device wrongly seen as "write protect is on"

[DervishD]

    Hi all :)

    I'm having a problem with an usb-storage device (namely a Inovix
IMP65 MP3 player): when I plug it and I try to mount it, the sd_mod
driver sees it write protected, so I cannot mount it read-write.

    If I remount it as read-write (as root, of course), I have
success and I can use the device normally, being able to write to it
without problems. If, instead, I manually unload sd_mod and load it
again, then this time the device is NOT seen as write protected (the
sd_mod driver says that "write protect is off").

    All this happens using kernel 2.4.32. If using Ubuntu kernel
2.6.15, the same problem happens, but Ubuntu probes the device twice
and the second time the "write protect is off" message appears. It
mounts the device "ro", anyway. I've tested with two different USB
ports, an ALi 2.0 (driver EHCI+OHCI) and a builtin VIA686 (driver
UHCI) with the same results.

    If I plug the device with the write protect switch on (that is,
the device IS *really* write protected), the sd_mod driver sees it as
"write protect is off" and I can mount it "rw"... but I cannot write
anything!

    The same device works OK in WinXP without any driver (well, with
the default USB disk driver), so I'm not sure if the problem is on
the device (in fact, it works OK after remounting "rw" by hand or
manually reloading sd_mod) or in the kernel drivers (which I find
very unlikely, since similar Inovix players work as-is).

    If you need more information, feel free to ask, and if this is a
known issue I will very happy if you could point me to the
appropriate place. I've googled a bit with no success...

    Thanks a lot in advance.

    Raúl Núñez de Arenas Coronado

-- 
Linux Registered User 88736 | http://www.dervishd.net
http://www.pleyades.net & http://www.gotesdelluna.net
It's my PC and I'll cry if I want to... RAmen!

[Solved] usb-storage device wrongly seen as "write protect is on"

[DervishD]

    Hi all :)

 * DervishD <privado@dervishd.net> dixit:
>     I'm having a problem with an usb-storage device (namely a Inovix
> IMP65 MP3 player): when I plug it and I try to mount it, the sd_mod
> driver sees it write protected, so I cannot mount it read-write.
> 
>     If I remount it as read-write (as root, of course), I have
> success and I can use the device normally, being able to write to it
> without problems. If, instead, I manually unload sd_mod and load it
> again, then this time the device is NOT seen as write protected (the
> sd_mod driver says that "write protect is off").

    Well, after following Alan Stern's suggestion and making a trace
of what was happening using usbmon, the problem was solved.

    The stupid device is probably sharing firmware with another model
with SD card or whatever, and tells the kernel it has removable media
inside! Of course the kernel believes that. During the first two
polls (sometimes only the first poll, at least in 2.4.x) the device
reports that the media is write protected. Probably it doesn't want
to accept any WRITE commands until the "removable media" is settled,
or whatever...

    After that, it reports a media change and voilá, the "new" media
is no longer write-protected.

    I don't know why it worked in WinXP and MacOS, but now it works
in my 2.4 kernel. I just do the following:

    $ mount /media/mp3; umount /media/mp3; mount /media/mp3

    The second mount will see the media as write-enabled and will
mount it read-write. Cool!

    Thanks a lot to Alan Stern for solving my problem and showing so
much interest in the issue. And thanks to Andrew Morton, too, for
forwarding my message to the USB developers list :)

    Raúl Núñez de Arenas Coronado

-- 
Linux Registered User 88736 | http://www.dervishd.net
http://www.pleyades.net & http://www.gotesdelluna.net
It's my PC and I'll cry if I want to... RAmen!