Hi Henrique, Sorry for top-posting, I CC Aurélien and Didier as they are dealing with usb-modeswitch which plays the same role as ozerocdoff hence leave your full answer below.
Thanks for your help and explanations. I think we can work with both Aurélien and Didier to fill these bugs. If we can avoid using userspace utilities (be it rezero, oozerocdoff or usb-modeswitch), that would indeed be great, but do you think kernel developers will agree to completely de-activate CD emulation possibilities? Don't you think they **might** have a use for Linux users in the future? Again, many thanks! Julien Le samedi 21 février 2009 à 10:30 -0300, Henrique de Moraes Holschuh a écrit : > On Sat, 21 Feb 2009, Julien Valroff wrote: > > 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. > > Fair enough. > > > > 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. > > [... ozerocdoff readme below ...] > > > The Linux OS does currently not use this ZERO-CD, because the image can > > not hold all the needed binary kernel drivers, which > > And it never will, it is just plain impossible. Source it could hold, but > that's useless from a normal user perspective, so it is a completely useless > feature for Linux, and it can be unconditionally disabled on all WWAN modems > (not just "Option WWAN"), IMO. > > That makes it the kernel's business. I am not against Debian adding these > userspace utilities, mind you (so I am not against your ITP), they will be > needed for at least one year... > > > 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. > > That's the clinch, then. It only becomes usable after the cdrom emulator is > disabled, so the kernel driver is incomplete if it doesn't do it (again, > IMO). > > > 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. > > This is a kernel deficiency, and it can and should be fixed (if it isn't > already by adding quirks to the option module or whatever). > > > 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. > > This should also be fixed in the kernel, and appears to be a consequence of > the stuff above. > > > 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 > > This is ALSO a kernel bug that needs to be fixed, unless "a hard disconnect" > is something that violates some spec, which I very much doubt, since SCSI is > supposed to support target-initiated disconnection. > > [...] > > > 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 > > Again, stuff that needs to be fixed in the kernel properly. > > You can file a bug on bugzilla.kernel.org, mentioning this mailinglist > thread, AND attaching the ozerocdoff README (make it clear that it explains > the hoops that are being done to get that hardware to work). > > You need two bugs: one for the "usb-storage might freeze on a SCSI hard > disconnect from an "Option WWAN Modem with an emulated CDROM mass-storage > device", and the other for the rest of the stuff dealing with the "option" > module not doing the right thing to *select* the proper module to drive the > "Option WWAN modem". > > Or you can file the two bugs against the Debian kernel, tag them upstream, > and ask the Debian kernel maintainers to forward it upstream (write THAT on > the top of the bug reports, or someone might thing by mistake that the > upstream tag means you have already forwarded it upstream, etc). > -- Membre de l'April - « promouvoir et défendre le logiciel libre » - http://www.april.org Rejoignez maintenant plus de 4 000 personnes, associations, entreprises et collectivités qui soutiennent notre action -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
