Bug#516258: ITP: ozerocdoff -- temporarily disables ZeroCD
Hi Henrique,
Le vendredi 20 février 2009 à 21:54 -0300, Henrique de Moraes Holschuh a
écrit :
> On Fri, 20 Feb 2009, Julien Valroff wrote:
> > The new USB Option WWAN modem device support a CDROM device, which holds
> > the needed Windows driver to use the WWAN modem.
> >
> > Therefore the firmware of the WWAN modem announce during the USB enumeration
> > process to work as a virtual CDROM device with its vendor name "ZOPTION".
> >
> > This device is now called ZERO-CD.
> >
> > ozerocdoff is a solution to switch off the ZERO-CD and allow the modem to
> > be a modem.
>
> Why is it needed? Are there devices that malfunction as modems while the
> emulated cdrom is active?
Yes.
> I ask because I have tested a bunch of Huawei E226, which do have this
> stupid cdrom emulation hack from hell to bypass Windows security policies.
> While option does allow it to register the mass storage device with
> usb-storage, it also works as a GSM modem just fine at the same time...
That is not the case of (at least) Option WWAN modems.
> If there is a pressing need to disable that stupid emulated cdrom, maybe a
> bug should be filled to fix it right in the kernel, so that the emulated
> device is never bound to usb-storage to begin with?
I attach the original README file shipped with ozerocdoff, which
explains much better than I could.
I have also been discussing with Aurélien GÉRÔME who has recently
sponsored usb-modeswitch, which is now in NEW -
http://ftp-master.debian.org/new/usb-modeswitch_0.9.6-1.html
It has the same role but for more devices than ozerocdoff - we have
however concluded that it could be great to have both of them in Debian.
As regarding fixing the kernel, I fear I do not have the skills to judge
whether this would be appropriate (or possible) or not. I would be glad
to get some help on this.
Cheers,
Julien
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Switch off ZERO-CD:
The new USB Option WWAN modem device support a CDROM device, which holds the needed Windows driver to use the WWAN modem.
Therefore the firmware of the WWAN modem announce during the USB enumeration process to work as a virtual CDROM device with
its vendor name "ZOPTION". This device is now called ZERO-CD.
The Linux OS does currently not use this ZERO-CD, because the image can not hold all the needed binary kernel drivers, which
may exists in the world. Also it is often strange to identify the exact matching drivers to your system, because the 2.6.xx
kernel has today a lot of Distro specific patches. So we will currently not use this ZERO-CD device for Linux and have to switch
it off. Once you send this switch off command to the WWAN modem, another new USB enumeration will be requested by the WWAN modem
firmware. Afterwards the real WWAN modem interface is available on the USB bus.
Looking on the Linux USB core system, it has another restriction. If there are more than one possible drivers, which can work
successfully with that USB WWAN modem, the USB core system will allow probing the WWAN modem by these drivers in a special order.
First the already loaded driver will be allowed to do the probe. If then this driver do a successful probe, another potential
driver will never become a chance to do also a probing with that hardware. Therefore it is (currently) impossible to use the final
WWAN modem driver to send the ZERO-CD switch off command, because often the USB mass storge driver will be already loaded and
is working in your Linux system.
If the probing of an already loaded module is not successful or no module is loaded, the udev system will trigger a modeprobe
to load the needed driver(s). But the loading order of the drivers is not clear specified, although is may depends on the order
of the appearance in the modules dependency files created by depmod.
But this probe order is also important to know for some old Option WWAN modems, which could be handled by the mainstream 'option'
kernel driver. Unfortunately this is a bug, because the mainstream 'option' driver looks on the wrong USB device ID.
Solution switch off the ZERO-CD:
The ZERO-CD switch off command is simple a SCSI 'rezero' command. The easiest way to send this command to the WWAN modem is by
using the standard Linux USB mass storage driver. Because the WWAN modem will initiate a hard disconnect from the SCSI bus
connection after receiving that rezero command and the USB mass storage driver is not prepared for such a situation, we risk
a possible system freeze.
Therefore we use a short C-program 'ozerocdoff', based on the Linux USB lib together with some special udev rules. These rules
ensure a USB mass storage disconnection in the very early communication state, often in the time frame, when this driver waits
for a bus stabilization. Naturally we test,
- if only a known USB device ID is used, which ensures the driver can support also the plugged-in WWAN modem
- if parts of the USB device address match, which ensures proper ZERO-CD disabling for the correct device
- if the device is really in ZERO-CD mode
The ozerocd can be easy compiled by calling the Makefile. You find also a short man page, which explains the usage of the ozerocdoff
tool. Note that you must call the ozerocdoff as root user.
The trick is now to tell the Linux udev hotplug system to look carefully on a new USB device, which announce to be a CDROM device.
We check here only the USB vendor and device ID and have not to wait for a CDROM vendor option like "ZOPTION" to guarantee starting
the ozerocdoff program as early as possible. Otherwise the USB SCSI mass storage driver would need to do communication to the WWAN-
modem which is here not really needed. If the udev system detects such a device, it has to start simply ozercdoff program, which
do additional test on that found USB device, disconnects the USB SCSI mass storage driver, sends the rezero command and finally checks
if the WWAN-modem has properly switch to its WWAN modem interface.
The automatic triggering will be done by a udev rule. An example can be found here in the file:
hso.udev
This file has to be copied as '049_hso-udev.rules' file into the
/etc/udev/rules.d/
directory. Finally don't forget to tell the udev system to reload its rule files. This can be done by
udevcontrol reload_rules
Solution use the correct HSO Option driver:
Because we have now two drivers for some Option WWAN-modems, we simply blacklist the mainstream 'option' kernel module driver, which
we do not like to use. Note that this 'option' driver does support only Option WWAN modem with Version 3 Interface, which support
only virtual serial modem ports. The new 'hso' driver supports the newer Version 4 Interface. Here also an IP network device is
available, which allow high speed communication also by using the slow USB 1.1 bus system. Note also that this network interface is
not identical to a virtual ethernet, because it "speaks" only IP. So e.g. running a dhcpclient is here not possible, because this would
require the support of the simple ether transport package frames.
The 'option' mainstream driver can be prevent to be automatically loaded be adding a line like:
blacklist option
in the blacklist file found here:
/etc/modprobe.d/blacklist
But note that this will not unload a currently running 'option' driver. This has to be done by the commands:
rmmod option
lsmod | grep option
The 2nd grep to the option kernel module should not find a 'option' driver still loader. Otherwise the driver maybe currently in usage
and the 'option' driver can not be successfully unloaded. Then please unplug your WWAN modem and repeat the procedure.
Auto Linking device node with self-explanatory names:
This 'hso' driver supports 'self-explanatory' device node names. Because of the big number of different virtual serial device
nodes, which will be supported by some WWAN modems and modem firmware, specially optional ports will not always match to the same
numbered device node. E.g. the serial modem port can be /dev/ttyHS3 or for another firmware /dev/ttyHS4.
Some important links to device node names are:
/dev/wmodem0 : the /dev/tty modem interface
/dev/wapp0 : the /dev/tty application port
/dev/wctrl0 : the /dev/tty control port
Note that currently only one plugged-in WWAN modem is supported. In the future also more than one WWAN modem can be supported. The
2nd WWAN modem tty port would than be called '/dev/wmodem1'.
WWAN Net device:
This 'hso' driver supports the WWAN like an Ethernet device. Additionlly this ethernet port is registered in sysfs. Normerlly the
hald distinguish only between 802.03 wired Ethernet and 802.11 Wireless Ethernet. The 10-wwan-quirk.fdi enables now also support of
WWAN devices by the hald. this is especially needed fot the Network Manager. It detects the network category entry and would use
a WWAN modem as wireed device without that fdi quirk.
The 10-wwan-quirk.fdi should be copied into the /usr/share/hal/fdi/information/20thirdparty directory.
Naturally this fdi quirk should be exchanged by a new version of the hald. But the hald new a mechanism, how it can distguish
between wirless 802.11, wired 802.03 and wwan devices. Therefore and currently not enabled dpatch is part of the module package.
It could be enabled, if the following line will be part of the debian/patches/00list.hso_modules
02_hso_modules_sysfs_wwan_dir
Please add this line and rebuild the whole debian package. It will add a subdirectory "wwan" in the /sys/class/net/hso0/ sysfs
directory.
WWAM USB suspend:
The older driver package does not enable automatic entering USB suspend state after a short configurable timeout. But now the hso
driver will be load with the extra option "enable_autopm=1". Although this option could be set after loading the driver, it is very
important to set it just _before_ the device will be probed. So enabling this module parameter by an udev rule would only work as
long as the WWAN device has an enabled ZERO-CD device. Only in that case the udev rule will be used processed twice and just before
the 2nd and final device WWAN modem device probe will be done.
Anyway a udev rule will setup the suspend timeout value found in the configuration file from
/etc/hso-suspend.conf
and copy it into the corresponding USB core sysfs /power/autosuspend property. The osetsuspend script will handle this. The same
script can be used to change manually the time value or disable automatic suspend.
The complete solution:
All that installation and configuration stuff will be done automatically, if you install the Debian hso-udev package in you system.
Because this little helper tool and script does not make you happy without the driver, the hso-udev package requires also to install
a Debian binary HSO kernel module, which is part of the hso-module package.
Note that the HSO kernel binary module has to match exactly you current Distro kernel sub release. Otherwise you system may crash.
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