From: Dan Williams <dcbw@redhat.com>
To: Arnd Bergmann <arnd@arndb.de>, Johannes Berg <johannes@sipsolutions.net>
Cc: DTML <devicetree@vger.kernel.org>,
syadagir@codeaurora.org, Eric Caruso <ejcaruso@google.com>,
linux-arm-msm@vger.kernel.org, abhishek.esse@gmail.com,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
evgreen@chromium.org,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Ilias Apalodimas <ilias.apalodimas@linaro.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Alex Elder <elder@linaro.org>,
Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>,
Networking <netdev@vger.kernel.org>,
linux-soc@vger.kernel.org, David Miller <davem@davemloft.net>,
cpratapa@codeaurora.org, Ben Chan <benchan@google.com>
Subject: Re: [PATCH v2 00/17] net: introduce Qualcomm IPA driver
Date: Tue, 11 Jun 2019 10:53:57 -0500 [thread overview]
Message-ID: <fc0d08912bc10ad089eb74034726308375279130.camel@redhat.com> (raw)
In-Reply-To: <CAK8P3a0kV-i7BJJ2X6C=5n65rSGfo8fUiC4J_G-+M8EctYKbkg@mail.gmail.com>
On Tue, 2019-06-11 at 13:56 +0200, Arnd Bergmann wrote:
> On Tue, Jun 11, 2019 at 10:12 AM Johannes Berg
> <johannes@sipsolutions.net> wrote:
>
> > > As I've made clear before, my work on this has been focused on
> > > the IPA transport,
> > > and some of this higher-level LTE architecture is new to me. But
> > > it
> > > seems pretty clear that an abstracted WWAN subsystem is a good
> > > plan,
> > > because these devices represent a superset of what a "normal"
> > > netdev
> > > implements.
> >
> > I'm not sure I'd actually call it a superset. By themselves, these
> > netdevs are actually completely useless to the network stack,
> > AFAICT.
> > Therefore, the overlap with netdevs you can really use with the
> > network
> > stack is pretty small?
>
> I think Alex meant the concept of having a type of netdev with a
> generic
> user space interface for wwan and similar to a wlan device, as I
> understood
> you had suggested as well, as opposed to a stacked device as in
> rmnet or those drivers it seems to be modeled after (vlan, ip tunnel,
> ...)/.
>
> > > HOWEVER I disagree with your suggestion that the IPA code should
> > > not be committed until after that is all sorted out. In part
> > > it's
> > > for selfish reasons, but I think there are legitimate reasons to
> > > commit IPA now *knowing* that it will need to be adapted to fit
> > > into the generic model that gets defined and developed. Here
> > > are some reasons why.
> >
> > I can't really argue with those, though I would point out that the
> > converse also holds - if we commit to this now, then we will have
> > to
> > actually keep the API offered by IPA/rmnet today, so we cannot
> > actually
> > remove the netdev again, even if we do migrate it to offer support
> > for a
> > WWAN framework in the future.
>
> Right. The interface to support rmnet might be simple enough to keep
> next to what becomes the generic interface, but it will always
> continue
> to be an annoyance.
>
> > > Second, the IPA code has been out for review recently, and has
> > > been
> > > the subject of some detailed discussion in the past few
> > > weeks. Arnd
> > > especially has invested considerable time in review and
> > > discussion.
> > > Delaying things until after a better generic model is settled on
> > > (which I'm guessing might be on the order of months)
> >
> > I dunno if it really has to be months. I think we can cobble
> > something
> > together relatively quickly that addresses the needs of IPA more
> > specifically, and then extend later?
> >
> > But OTOH it may make sense to take a more paced approach and think
> > about the details more carefully than we have over in the other
> > thread so far.
>
> I would hope that as soon as we can agree on a general approach, it
> would also be possible to merge a minimal implementation into the
> kernel
> along with IPA. Alex already mentioned that IPA in its current state
> does
> not actually support more than one data channel, so the necessary
> setup for it becomes even simpler.
>
> At the moment, the rmnet configuration in
> include/uapi/linux/if_link.h
> is almost trivial, with the three pieces of information needed being
> an IFLA_LINK to point to the real device (not needed if there is only
> one device per channel, instead of two), the IFLA_RMNET_MUX_ID
> setting the ID of the muxing channel (not needed if there is only
> one channel ?), a way to specify software bridging between channels
> (not useful if there is only one channel) and a few flags that I
> assume
> must match the remote end:
>
> #define RMNET_FLAGS_INGRESS_DEAGGREGATION (1U << 0)
> #define RMNET_FLAGS_INGRESS_MAP_COMMANDS (1U << 1)
> #define RMNET_FLAGS_INGRESS_MAP_CKSUMV4 (1U << 2)
> #define RMNET_FLAGS_EGRESS_MAP_CKSUMV4 (1U << 3)
> enum {
> IFLA_RMNET_UNSPEC,
> IFLA_RMNET_MUX_ID,
> IFLA_RMNET_FLAGS,
> __IFLA_RMNET_MAX,
> };
> #define IFLA_RMNET_MAX (__IFLA_RMNET_MAX - 1)
> struct ifla_rmnet_flags {
> __u32 flags;
> __u32 mask;
> };
>
> > > Third, having the code upstream actually means the actual
> > > requirements
> > > for rmnet-over-IPA are clear and explicit. This might not be a
> > > huge
> > > deal, but I think it's better to devise a generic WWAN scheme
> > > that
> > > can refer to actual code than to do so with assumptions about
> > > what
> > > will work with rmnet (and others). As far as I know, the
> > > upstream
> > > rmnet has no other upstream back end; IPA will make it "real."
> >
> > Is that really true? I had previously been told that rmnet actually
> > does
> > have use with a few existing drivers.
> >
> >
> > If true though, then I think this would be the killer argument *in
> > favour* of *not* merging this - because that would mean we *don't*
> > have
> > to actually keep the rmnet API around for all foreseeable future.
>
> I would agree with that. From the code I can see no other driver
> including the rmnet protocol header (see the discussion about moving
> the header to include/linux in order to merge ipa), and I don't see
> any other driver referencing ETH_P_MAP either. My understanding
> is that any driver used by rmnet would require both, but they are
> all out-of-tree at the moment.
The general plan (and I believe Daniele Palmas was working on it) was
to eventually make qmi_wwan use rmnet rather than its internal sysfs-
based implementation. qmi_wwan and ipa are at essentially the same
level and both could utilize rmnet on top.
*That's* what I'd like to see. I don't want to see two different ways
to get QMAP packets to modem firmware from two different drivers that
really could use the same code.
Dan
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next prev parent reply other threads:[~2019-06-11 15:54 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-31 3:53 [PATCH v2 00/17] net: introduce Qualcomm IPA driver Alex Elder
2019-05-31 3:53 ` [PATCH v2 01/17] bitfield.h: add FIELD_MAX() and field_max() Alex Elder
2019-05-31 3:53 ` [PATCH v2 02/17] dt-bindings: soc: qcom: add IPA bindings Alex Elder
2019-06-10 22:08 ` Rob Herring
2019-06-11 2:11 ` Alex Elder
2019-07-03 15:09 ` Alex Elder
2019-05-31 3:53 ` [PATCH v2 03/17] soc: qcom: ipa: main code Alex Elder
2019-05-31 21:50 ` David Miller
2019-05-31 22:25 ` Alex Elder
2019-05-31 3:53 ` [PATCH v2 04/17] soc: qcom: ipa: configuration data Alex Elder
2019-05-31 3:53 ` [PATCH v2 05/17] soc: qcom: ipa: clocking, interrupts, and memory Alex Elder
2019-05-31 3:53 ` [PATCH v2 06/17] soc: qcom: ipa: GSI headers Alex Elder
2019-05-31 3:53 ` [PATCH v2 07/17] soc: qcom: ipa: the generic software interface Alex Elder
2019-05-31 3:53 ` [PATCH v2 08/17] soc: qcom: ipa: GSI transactions Alex Elder
2019-05-31 3:53 ` [PATCH v2 09/17] soc: qcom: ipa: IPA interface to GSI Alex Elder
2019-05-31 3:53 ` [PATCH v2 10/17] soc: qcom: ipa: IPA endpoints Alex Elder
2019-05-31 3:53 ` [PATCH v2 11/17] soc: qcom: ipa: immediate commands Alex Elder
2019-05-31 3:53 ` [PATCH v2 12/17] soc: qcom: ipa: IPA network device and microcontroller Alex Elder
2019-05-31 3:53 ` [PATCH v2 13/17] soc: qcom: ipa: AP/modem communications Alex Elder
2019-05-31 3:53 ` [PATCH v2 14/17] soc: qcom: ipa: support build of IPA code Alex Elder
2019-05-31 3:53 ` [PATCH v2 15/17] MAINTAINERS: add entry for the Qualcomm IPA driver Alex Elder
2019-05-31 3:53 ` [PATCH v2 16/17] arm64: dts: sdm845: add IPA information Alex Elder
2019-05-31 3:53 ` [PATCH v2 17/17] arm64: defconfig: enable build of IPA code Alex Elder
2019-05-31 14:58 ` [PATCH v2 00/17] net: introduce Qualcomm IPA driver Dan Williams
2019-05-31 16:36 ` Alex Elder
2019-05-31 19:19 ` Arnd Bergmann
2019-05-31 20:47 ` Alex Elder
2019-05-31 21:12 ` Arnd Bergmann
2019-05-31 22:08 ` Alex Elder
2019-06-07 17:43 ` Alex Elder
2019-05-31 23:33 ` Bjorn Andersson
2019-05-31 23:59 ` Subash Abhinov Kasiviswanathan
2019-06-03 10:04 ` Arnd Bergmann
2019-06-03 13:32 ` Alex Elder
2019-06-04 8:13 ` Arnd Bergmann
2019-06-04 15:18 ` Dan Williams
2019-06-04 20:04 ` Arnd Bergmann
2019-06-04 21:29 ` Dan Williams
2019-06-06 17:42 ` Alex Elder
2019-06-11 8:12 ` Johannes Berg
2019-06-11 11:56 ` Arnd Bergmann
2019-06-11 15:53 ` Dan Williams [this message]
2019-06-11 16:52 ` Subash Abhinov Kasiviswanathan
2019-06-11 17:22 ` Dan Williams
2019-06-12 8:31 ` Arnd Bergmann
2019-06-12 14:27 ` Dan Williams
2019-06-12 15:06 ` Arnd Bergmann
2019-06-17 11:42 ` Johannes Berg
2019-06-17 12:25 ` Johannes Berg
2019-06-18 15:20 ` Alex Elder
2019-06-18 18:06 ` Dan Williams
2019-06-24 16:21 ` Alex Elder
2019-06-25 14:14 ` Johannes Berg
2019-06-26 13:36 ` Alex Elder
2019-06-26 17:55 ` Johannes Berg
2019-06-18 18:48 ` Johannes Berg
2019-06-24 16:21 ` Alex Elder
2019-06-18 13:45 ` Alex Elder
2019-06-18 19:03 ` Johannes Berg
2019-06-18 20:09 ` Arnd Bergmann
2019-06-18 20:15 ` Johannes Berg
2019-06-18 20:33 ` Arnd Bergmann
2019-06-18 20:39 ` Johannes Berg
2019-06-18 21:06 ` Arnd Bergmann
2019-06-19 20:56 ` Dan Williams
2019-06-24 16:21 ` Alex Elder
2019-06-24 16:40 ` Arnd Bergmann
2019-06-25 14:19 ` Johannes Berg
2019-06-26 13:39 ` Alex Elder
2019-06-26 13:58 ` Arnd Bergmann
2019-06-26 17:48 ` Johannes Berg
2019-06-26 17:45 ` Johannes Berg
2019-06-26 13:51 ` Alex Elder
2019-06-17 11:28 ` Johannes Berg
2019-06-18 13:16 ` Alex Elder
2019-06-18 13:48 ` Arnd Bergmann
2019-06-18 19:14 ` Johannes Berg
2019-06-18 19:59 ` Arnd Bergmann
2019-06-18 20:36 ` Johannes Berg
2019-06-18 20:55 ` Arnd Bergmann
2019-06-18 21:02 ` Johannes Berg
2019-06-18 21:15 ` Subash Abhinov Kasiviswanathan
2019-06-19 12:23 ` Arnd Bergmann
2019-06-19 18:47 ` Subash Abhinov Kasiviswanathan
2019-06-20 1:25 ` Dan Williams
2019-06-24 16:21 ` Alex Elder
2019-06-17 12:14 ` Johannes Berg
2019-06-18 14:00 ` Alex Elder
2019-06-18 19:22 ` Johannes Berg
2019-06-24 16:21 ` Alex Elder
2019-06-03 14:50 ` Dan Williams
2019-06-03 14:54 ` Dan Williams
2019-06-03 15:52 ` Alex Elder
2019-06-03 16:18 ` Dan Williams
2019-06-03 19:04 ` Subash Abhinov Kasiviswanathan
2019-06-04 15:21 ` Dan Williams
2019-05-31 23:27 ` Bjorn Andersson
2019-06-10 2:44 ` Alex Elder
2019-06-20 13:41 ` [PATCH v2 05/17] soc: qcom: ipa: clocking, interrupts, and memory Hillf Danton
2019-06-24 16:30 ` WWAN Controller Framework (was IPA [PATCH v2 00/17]) Alex Elder
2019-06-24 17:06 ` Alex Elder
2019-06-25 14:34 ` Johannes Berg
2019-06-26 13:40 ` Alex Elder
2019-06-26 17:58 ` Johannes Berg
2019-06-24 19:54 ` Dan Williams
2019-06-24 21:16 ` Alex Elder
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