Dave Jones <[email protected]> writes: > Hi Bjørn, > > > Gitweb: > http://git.kernel.org/linus/;a=commit;h=1e8bbe6cd02fc300c88bd48244ce61ad9c7d1776 > > Commit: 1e8bbe6cd02fc300c88bd48244ce61ad9c7d1776 > > Parent: a5b8db91442fce9c9713fcd656c3698f1adde1d6 > > Author: Bjørn Mork <[email protected]> > > AuthorDate: Thu Mar 14 01:05:13 2013 +0000 > > Committer: David S. Miller <[email protected]> > > CommitDate: Sun Mar 17 11:59:03 2013 -0400 > > > > net: cdc_ncm, cdc_mbim: allow user to prefer NCM for backwards > compatibility > > > > commit bd329e1 ("net: cdc_ncm: do not bind to NCM compatible MBIM > devices") > > introduced a new policy, preferring MBIM for dual NCM/MBIM functions if > > the cdc_mbim driver was enabled. This caused a regression for users > > wanting to use NCM. > > > > Devices implementing NCM backwards compatibility according to section > > 3.2 of the MBIM v1.0 specification allow either NCM or MBIM on a single > > USB function, using different altsettings. The cdc_ncm and cdc_mbim > > drivers will both probe such functions, and must agree on a common > > policy for selecting either MBIM or NCM. Until now, this policy has > > been set at build time based on CONFIG_USB_NET_CDC_MBIM. > > > > Use a module parameter to set the system policy at runtime, allowing > the > > user to prefer NCM on systems with the cdc_mbim driver. > > Is there any way we can set this automatically based on the type of device > connected > and have it just work without users needing to edit modprobe.conf ? > > Since this change, we've now getting reports like > https://bugzilla.redhat.com/show_bug.cgi?id=963663
Yes, this is a very unfortunate side effect of the userspace/kernel split of the MBIM driver combined with the NCM/MBIM "backwards compatibility" setting. Which in itself is a bad idea, IMHO. I recommend all distros do the same as Debian: Set NCM as default until a userspace application with MBIM support is ready and packaged in the distro: http://anonscm.debian.org/viewvc/kernel/dists/trunk/linux/debian/patches/debian/cdc_ncm-cdc_mbim-use-ncm-by-default.patch FWIW, I wish we would have thought about this issue before v3.8 was released. Then we could have made that patch the mainline default, without that being a userspace API change. But we didn't. The good news is that Aleksander has done some nice work on the MBIM support in ModemManager, so there is a good chance that the next release will make this problem go away. Bjørn -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
