From: Alan Stern <stern@rowland.harvard.edu>
To: Andrew Bresticker <abrestic@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
"linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>,
<devicetree@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
<linux-usb@vger.kernel.org>, Rob Herring <robh+dt@kernel.org>,
Pawel Moll <pawel.moll@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Ian Campbell <ijc+devicetree@hellion.org.uk>,
Kumar Gala <galak@codeaurora.org>,
Stephen Warren <swarren@wwwdotorg.org>,
Thierry Reding <thierry.reding@gmail.com>,
Russell King <linux@arm.linux.org.uk>,
Peter De Schrijver <pdeschrijver@nvidia.com>,
Prashant Gaikwad <pgaikwad@nvidia.com>,
Mike Turquette <mturquette@linaro.org>,
Kishon Vijay Abraham I <kishon@ti.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Mathias Nyman <mathias.nyman@intel.com>,
Grant Likely <grant.likely@linaro.org>,
Randy Dunlap <rdunlap@infradead.org>
Subject: Re: [RFC PATCH 06/10] usb: xhci: Add Tegra XHCI host-controller driver
Date: Thu, 15 May 2014 17:16:01 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1405151709100.887-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <CAL1qeaHm7U2NVDeVZS-Tiz5ntkk4c13RR_1ws9MTYGGoGCOB5A@mail.gmail.com>
On Thu, 15 May 2014, Andrew Bresticker wrote:
> > This does not feel appropriate at all: Rather than creating a child device,
> > you should have a specific driver that hooks into functions exported
> > by the xhci core. See Documentation/driver-model/design-patterns.txt
>
> This is how DWC3, currently the only in-tree non-PCI XHCI host driver,
> is structured - see drivers/usb/dwc3/host.c. The recently proposed
> Armada XHCI driver [1] just adds clock support and a hook in
> xhci-plat's probe() to do the platform-specific initialization.
> Tegra's XHCI driver initialization is quite a bit more complicated,
> mainly due to the need for external firmware and specific ordering
> (e.g. firmware messages should only be enabled after the HCD is
> created). I could do away with the xhci-plat sub-device and just
> create a Tegra hc_driver, but it seems silly to have three XHCI
> platform drivers structured in three different ways. USB folks, do
> you have an opinion on how this should be done?
Felipe and I have differing opinions. I prefer not to create an extra
device level, and he does (that's why the non-PCI EHCI drivers don't do
it and the dwc3 driver does). I consider Felipe's approach to be an
example of the "Midlayer Mistake" anti-pattern from the LWN
article mentioned earlier in this thread -- I don't know what he thinks
about my approach.
Anyway, unless I'm totally mistaken, you wouldn't end up with three
platform drivers structured in three different ways. Either way, your
new driver would be structured like one of the existing two.
Alan Stern
next prev parent reply other threads:[~2014-05-15 21:16 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-15 0:32 [RFC PATCH 00/10] Tegra XHCI support Andrew Bresticker
2014-05-15 0:32 ` [RFC PATCH 01/10] clk: tegra: Enable hardware control of PLLE Andrew Bresticker
2014-05-15 0:32 ` [RFC PATCH 02/10] clk: tegra: Fix xusb_fs_src mux Andrew Bresticker
2014-05-15 0:32 ` [RFC PATCH 03/10] clk: tegra: Fix xusb_hs_src clock hierarchy Andrew Bresticker
2014-05-15 0:33 ` [RFC PATCH 04/10] clk: tegra: Initialize xusb clocks Andrew Bresticker
2014-05-15 19:22 ` Stephen Warren
2014-05-20 15:41 ` Peter De Schrijver
2014-05-15 0:33 ` [RFC PATCH 05/10] ARM: tegra: Export function to read USB calibration data Andrew Bresticker
2014-05-15 20:39 ` Stephen Warren
2014-05-15 0:33 ` [RFC PATCH 06/10] usb: xhci: Add Tegra XHCI host-controller driver Andrew Bresticker
2014-05-15 8:17 ` Arnd Bergmann
2014-05-15 9:19 ` Thierry Reding
2014-05-15 13:30 ` Arnd Bergmann
2014-05-15 20:18 ` Andrew Bresticker
2014-05-15 21:16 ` Alan Stern [this message]
2014-05-15 21:18 ` Thierry Reding
2014-05-16 16:52 ` Andrew Bresticker
2014-05-15 0:33 ` [RFC PATCH 07/10] phy: Add Tegra XUSB PHY driver Andrew Bresticker
2014-05-15 0:33 ` [RFC PATCH 08/10] ARM: tegra124: Bind CAR to syscon device Andrew Bresticker
2014-05-15 19:25 ` Stephen Warren
2014-05-15 20:22 ` Andrew Bresticker
2014-05-15 0:33 ` [RFC PATCH 09/10] ARM: tegra124: Add XHCI controller and PHY Andrew Bresticker
2014-05-15 0:33 ` [RFC PATCH 10/10] ARM: tegra124: Enable XHCI on Venice2 Andrew Bresticker
2014-05-15 19:33 ` [RFC PATCH 00/10] Tegra XHCI support Stephen Warren
2014-05-15 20:44 ` Andrew Bresticker
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