* Re: net: cdc_ncm, cdc_mbim: allow user to prefer NCM for backwards compatibility
@ 2013-05-16 18:25 Dave Jones
2013-05-16 19:08 ` Bjørn Mork
0 siblings, 1 reply; 5+ messages in thread
From: Dave Jones @ 2013-05-16 18:25 UTC (permalink / raw)
To: Linux Kernel Mailing List; +Cc: Bjørn Mork, netdev, Fedora Kernel Team
Hi Bjørn,
> Gitweb: http://git.kernel.org/linus/;a=commit;h=1e8bbe6cd02fc300c88bd48244ce61ad9c7d1776
> Commit: 1e8bbe6cd02fc300c88bd48244ce61ad9c7d1776
> Parent: a5b8db91442fce9c9713fcd656c3698f1adde1d6
> Author: Bjørn Mork <bjorn@mork.no>
> AuthorDate: Thu Mar 14 01:05:13 2013 +0000
> Committer: David S. Miller <davem@davemloft.net>
> 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
Dave
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: net: cdc_ncm, cdc_mbim: allow user to prefer NCM for backwards compatibility
2013-05-16 18:25 net: cdc_ncm, cdc_mbim: allow user to prefer NCM for backwards compatibility Dave Jones
@ 2013-05-16 19:08 ` Bjørn Mork
2013-05-16 19:17 ` Dave Jones
0 siblings, 1 reply; 5+ messages in thread
From: Bjørn Mork @ 2013-05-16 19:08 UTC (permalink / raw)
To: Dave Jones; +Cc: Linux Kernel Mailing List, netdev, Fedora Kernel Team
Dave Jones <davej@redhat.com> writes:
> Hi Bjørn,
>
> > Gitweb: http://git.kernel.org/linus/;a=commit;h=1e8bbe6cd02fc300c88bd48244ce61ad9c7d1776
> > Commit: 1e8bbe6cd02fc300c88bd48244ce61ad9c7d1776
> > Parent: a5b8db91442fce9c9713fcd656c3698f1adde1d6
> > Author: Bjørn Mork <bjorn@mork.no>
> > AuthorDate: Thu Mar 14 01:05:13 2013 +0000
> > Committer: David S. Miller <davem@davemloft.net>
> > 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
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: net: cdc_ncm, cdc_mbim: allow user to prefer NCM for backwards compatibility
2013-05-16 19:08 ` Bjørn Mork
@ 2013-05-16 19:17 ` Dave Jones
2013-05-16 19:23 ` Bjørn Mork
0 siblings, 1 reply; 5+ messages in thread
From: Dave Jones @ 2013-05-16 19:17 UTC (permalink / raw)
To: Bjørn Mork
Cc: Linux Kernel Mailing List, netdev, Fedora Kernel Team,
Ben Hutchings
On Thu, May 16, 2013 at 09:08:23PM +0200, Bjørn Mork wrote:
> 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
Thanks for the pointer. We'll pick that up for the Fedora 3.9 kernels.
Ben, does debian have a commits mailing list for kernel changes ?
> 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.
good news indeed!
thanks.
Dave
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: net: cdc_ncm, cdc_mbim: allow user to prefer NCM for backwards compatibility
2013-05-16 19:17 ` Dave Jones
@ 2013-05-16 19:23 ` Bjørn Mork
2013-05-16 19:35 ` Dave Jones
0 siblings, 1 reply; 5+ messages in thread
From: Bjørn Mork @ 2013-05-16 19:23 UTC (permalink / raw)
To: Dave Jones
Cc: Linux Kernel Mailing List, netdev, Fedora Kernel Team,
Ben Hutchings
Dave Jones <davej@redhat.com> writes:
> Ben, does debian have a commits mailing list for kernel changes ?
I'm not Ben, but I believe this is what you're looking for:
http://lists.alioth.debian.org/mailman/listinfo/kernel-svn-changes
Bjørn
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: net: cdc_ncm, cdc_mbim: allow user to prefer NCM for backwards compatibility
2013-05-16 19:23 ` Bjørn Mork
@ 2013-05-16 19:35 ` Dave Jones
0 siblings, 0 replies; 5+ messages in thread
From: Dave Jones @ 2013-05-16 19:35 UTC (permalink / raw)
To: Bjørn Mork
Cc: Linux Kernel Mailing List, netdev, Fedora Kernel Team,
Ben Hutchings
On Thu, May 16, 2013 at 09:23:08PM +0200, Bjørn Mork wrote:
> Dave Jones <davej@redhat.com> writes:
>
> > Ben, does debian have a commits mailing list for kernel changes ?
>
> I'm not Ben, but I believe this is what you're looking for:
> http://lists.alioth.debian.org/mailman/listinfo/kernel-svn-changes
perfect. thanks!
Dave
^ permalink raw reply [flat|nested] 5+ messages in thread
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2013-05-16 18:25 net: cdc_ncm, cdc_mbim: allow user to prefer NCM for backwards compatibility Dave Jones
2013-05-16 19:08 ` Bjørn Mork
2013-05-16 19:17 ` Dave Jones
2013-05-16 19:23 ` Bjørn Mork
2013-05-16 19:35 ` Dave Jones
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