From: Arnd Bergmann <arnd@arndb.de>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: Alex Elder <elder@linaro.org>, Dan Williams <dcbw@redhat.com>,
Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>,
abhishek.esse@gmail.com, Ben Chan <benchan@google.com>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
cpratapa@codeaurora.org, David Miller <davem@davemloft.net>,
DTML <devicetree@vger.kernel.org>,
Eric Caruso <ejcaruso@google.com>,
evgreen@chromium.org,
Ilias Apalodimas <ilias.apalodimas@linaro.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
linux-arm-msm@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-soc@vger.kernel.org, Networking <netdev@vger.kernel.org>,
syadagir@codeaurora.org
Subject: Re: [PATCH v2 00/17] net: introduce Qualcomm IPA driver
Date: Tue, 18 Jun 2019 22:33:48 +0200 [thread overview]
Message-ID: <CAK8P3a29+JKbDdS9ikhgaKa-AJ1qd1sDMTAfzivGh5wN4VL88A@mail.gmail.com> (raw)
In-Reply-To: <97cbfb3723607c95d78e25785262ae7b0acdb11c.camel@sipsolutions.net>
On Tue, Jun 18, 2019 at 10:15 PM Johannes Berg
<johannes@sipsolutions.net> wrote:
> On Tue, 2019-06-18 at 22:09 +0200, Arnd Bergmann wrote:
> > > One is the whole multi-function device, where a single WWAN device is
> > > composed of channels offered by actually different drivers, e.g. for a
> > > typical USB device you might have something like cdc_ether and the
> > > usb_wwan TTY driver. In this way, we need to "compose" the WWAN device
> > > similarly, e.g. by using the underlying USB device "struct device"
> > > pointer to tie it together.
> > >
> > > The other is something like IPA or the Intel modem driver, where the
> > > device is actually a single (e.g. PCIe) device and just has a single
> > > driver, but that single driver offers different channels.
> >
> > I would hope we can simplify this to expect only the second model,
> > where you have a 'struct device' corresponding to hardware and the
> > driver for it creates one wwan_device that user space talks to.
>
> I'm not sure.
>
> Fundamentally, we have drivers in Linux for the ethernet part, for the
> TTY part, and for whatever other part might be in a given USB multi-
> function device.
>
> > Clearly the multi-function device hardware has to be handled somehow,
> > but it would seem much cleaner in the long run to do that using
> > a special workaround rather than putting this into the core interface.
>
> I don't think it really makes the core interface much more complex or
> difficult though, and it feels easier than writing a completely
> different USB driver yet again for all these devices?
>
> As far as I understand from Dan, sometimes they really are no different
> from a generic USB TTY and a generic USB ethernet, except you know that
> if those show up together it's a modem.
>
> > E.g. have a driver that lets you create a wwan_device by passing
> > netdev and a tty chardev into a configuration interface, and from that
> > point on use the generic wwan abstraction.
>
> Yeah, but where do you hang that driver? Maybe the TTY function is
> actually a WWAN specific USB driver, but the ethernet is something
> generic that can also work with pure ethernet USB devices, and it's
> difficult to figure out how to tie those together. The modules could
> load in completely different order, or even the ethernet module could
> load but the TTY one doesn't because it's not configured, or vice versa.
That was more or less my point: The current drivers exist, but don't
lean themselves to fitting into a new framework, so maybe the best
answer is not to try fitting them.
To clarify: I'm not suggesting to write new USB drivers for these at all,
but instead keep three parts that are completely unaware of each other
a) a regular netdevice driver
b) a regular tty driver
c) the new wwan subsystem that expects a device to be created
from a hardware driver but knows nothing of a) and b)
To connect these together, we need one glue driver that implements
the wwan_device and talks to a) and b) as the hardware. There are
many ways to do that. One way would be to add a tty ldisc driver.
A small user space helper opens the chardev, sets the ldisc
and then uses an ldisc specific ioctl command to create a wwan
device by passing an identifier of the netdevice and then exits.
From that point on, you have a wwan device like any other.
Arnd
next prev parent reply other threads:[~2019-06-18 20:34 UTC|newest]
Thread overview: 105+ 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
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 [this message]
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
2019-06-24 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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