From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: [PATCH net,stable-3.8] net: cdc_ncm, cdc_mbim: allow user to prefer NCM for backwards compatibility Date: Fri, 15 Mar 2013 05:22:25 +0000 Message-ID: <1363324945.3937.144.camel@deadeye.wl.decadent.org.uk> References: <1363259113-6909-1-git-send-email-bjorn@mork.no> Mime-Version: 1.0 Content-Type: multipart/signed; micalg="pgp-sha512"; protocol="application/pgp-signature"; boundary="=-w7sMNTl3HtbzxBRBuu27" Cc: netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Greg Suarez , Alexey Orishko To: =?ISO-8859-1?Q?Bj=F8rn?= Mork Return-path: In-Reply-To: <1363259113-6909-1-git-send-email-bjorn-yOkvZcmFvRU@public.gmane.org> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org --=-w7sMNTl3HtbzxBRBuu27 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2013-03-14 at 12:05 +0100, Bj=C3=B8rn Mork wrote: > 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. >=20 > 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. >=20 > Use a module parameter to set the system policy at runtime, allowing the > user to prefer NCM on systems with the cdc_mbim driver. >=20 > Cc: Greg Suarez > Cc: Alexey Orishko > Reported-by: Geir Haatveit > Reported-by: Tommi Kyntola > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=3D54791 > Signed-off-by: Bj=C3=B8rn Mork > --- >=20 > We now have two users independently reporting this as a 3.8 regression, > so something needs to be done. I am not sure if adding a new module > parameter is acceptable for stable, but this problem is definitely a > regression and no other solutions came up in response to my RFC. >=20 > The only real alternative I see for stable, is disabling MBIM support > on any dual NCM/MBIM function. Which of course will be a regression > for any user wanting MBIM, making it unacceptable. [...] It definitely makes sense for this to be a run-time parameter. And the default seems correct for custom kernels. For a distribution kernel - at least for Debian, where we can't assume kernel and userland are always updated together - I think the compile-time default should be false, and the userland package (presumably ModemManager?) can install a modprobe.conf file to override that once it can handle MBIM. We handled KMS transitions in a similar way. I don't know that it's worth having a Kconfig option for that, though. Ben. --=20 Ben Hutchings Humans are not rational beings; they are rationalising beings. --=-w7sMNTl3HtbzxBRBuu27 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIVAwUAUUKwEee/yOyVhhEJAQr0Jg/+KJYVjRo44djD1Be0hH0rgRQ6rGUZ4DFP CneznTNXOU3tdOQ00wSHsgTkEQFYftuzjnt6FCic/OFLgVUU1syR1DjGrQdiPS81 oc/01FIDj5Vh5lgzHrfVWYT/7b+pAvEGmxGaG+9LvMLm6rtsHRxWs4UEG/uDXr4k 4kcCUZsak5VtbPfhdX4jjttjqMQ45UwfYUHci5jyH1DvfnwCdu2W99nTyNge1bei vgMORYz0JfTXPsthBwb2iCLqfjI91dKDDU1EY3QLZu/EYLl3UIrhUK2NyW51NHUs 22iCEWz/kK1V0WIiT4qYJZ7p3OQyPaDP6ZGSURYu8EtOlq/nzLSR20nrBY7h165l xfczvXsbzjslXNYAbWxN9GYy8xrBkz8Yz1l945ov+4RHDh0RmStlcFKqTpwynw+d hmHaZW9S4H1BZZJDL08nhAH5IpjOUNce9OPCRx7ITzXrSNvFUzL9KT9ps7TvGMhS IukS8mZ5ahKOMcvZiurhHYsJBsoXh1r6J7/FvBp+21OBho0/Tsn36fi2Tq7/riXK t5+V0jgAPIMZUXHJB+Rb4vAQ3TPo51FIpSG7+1RRvasw+gfBaKCcn5vgHx2ZRVof MNBT3lurXj3UejJA4zyhD4rievw8izx32GVVr9A/hr4VFTxg28oznDZOv4dEmZYK +GhO1/vS6yg= =WoOr -----END PGP SIGNATURE----- --=-w7sMNTl3HtbzxBRBuu27-- -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html