Re: [PATCH v2 00/17] net: introduce Qualcomm IPA driver

From: Dan Williams <dcbw@redhat.com>
To: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Cc: Alex Elder <elder@linaro.org>, Arnd Bergmann <arnd@arndb.de>,
	David Miller <davem@davemloft.net>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Ilias Apalodimas <ilias.apalodimas@linaro.org>,
	evgreen@chromium.org, Ben Chan <benchan@google.com>,
	Eric Caruso <ejcaruso@google.com>,
	cpratapa@codeaurora.org, syadagir@codeaurora.org,
	abhishek.esse@gmail.com, Networking <netdev@vger.kernel.org>,
	DTML <devicetree@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-soc@vger.kernel.org,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH v2 00/17] net: introduce Qualcomm IPA driver
Date: Tue, 04 Jun 2019 10:21:41 -0500	[thread overview]
Message-ID: <feb3d23718ea462d304369d718c6ed37da8a8f15.camel@redhat.com> (raw)
In-Reply-To: <c200581b8fc167f3a0c09ef6233b8d81@codeaurora.org>

On Mon, 2019-06-03 at 13:04 -0600, Subash Abhinov Kasiviswanathan
wrote:
> > > I can't (or won't) comment right now on whether IPA needs its own
> > > netdev for rmnet to use.  The IPA endpoints used for the modem
> > > network interfaces are enabled when the netdev is opened and
> > > disabled when closed.  Outside of that, TX and RX are pretty
> > > much immediately passed through to the layer below or above.
> > > IPA currently has no other net device operations.
> > 
> > I don't really have issues with the patchset underneath the netdev
> > layer. I'm interested in how the various bits present themselves to
> > userspace, which is why I am trying to tie this in with Johannes'
> > conversation about WWAN devices, netdevs, channels, and how the
> > various
> > drivers present API for creating data channels that map to
> > different
> > modem contexts.
> > 
> > So let me rephrase. If the control plane has set up the default
> > context
> > and sent a QMI Start Network message (or the network attached the
> > default one) and the resulting IP details are applied to the IPA
> > netdev
> > can things just start sending data? Or do we need to create an
> > rmnet on
> > top to get that working?
> > 
> > Dan
> 
> Hi Dan
> 
> All data from the hardware will have the MAP headers.
> We still need to create rmnet devs over the IPA netdev and use it
> for 
> the
> data path.
> The IPA netdev will pass on the packets which it receives from the 
> hardware
> and queue it to network stack where it will be intercepted by the
> rmnet rx handler.

Ok, so IPA only needs a netdev so that rmnet has something to
send/receive packets to/from? This gets even closer to the discussion
in "cellular modem driver APIs - take 2" from last week.

Dan