linux-kernel - Re: [PATCH v2] extcon: otg_gpio: add driver for USB OTG port controlled by GPIO(s)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 20 Feb 2015 13:36:06 -0600
From:	Felipe Balbi <balbi@...com>
To:	David Cohen <david.a.cohen@...ux.intel.com>
CC:	Linus Walleij <linus.walleij@...aro.org>,
	Robert Baldyga <r.baldyga@...sung.com>,
	<heikki.krogerus@...ux.intel.com>,
	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	<baolu.lu@...ux.intel.com>, <balbi@...com>
Subject: Re: [PATCH v2] extcon: otg_gpio: add driver for USB OTG port
 controlled by GPIO(s)

On Fri, Feb 20, 2015 at 11:17:00AM -0800, David Cohen wrote:
> Hi Linus and Robert,
> 
> CC'ing Heikki as it involves a RFC from him.
> 
> On Fri, Feb 20, 2015 at 10:53:44AM +0100, Linus Walleij wrote:
> > On Fri, Feb 20, 2015 at 7:41 AM, Robert Baldyga <r.baldyga@...sung.com> wrote:
> > > Hi David,
> > >
> > > On 02/19/2015 08:59 PM, David Cohen wrote:
> > >> Some Intel platforms have an USB OTG port fully (or partially)
> > >> controlled by GPIOs:
> > >>
> > >> (1) USB ID is connected directly to a pulled up GPIO.
> > >>
> > >> Optionally:
> > >> (2) VBUS is enabled/disabled by a GPIO
> > >> (3) Platform has 2 USB controllers connected to same port: one for
> > >>     device and one for host role. D+/- are switched between phys.
> > >>     according to this GPIO level.
> > >>
> > >> This driver configures USB OTG port for device or host role according to
> > >> USB ID value.
> > >>  - If USB ID's GPIO level is low, OTG port is configured for host role
> > >>    by sourcing VBUS and switching D+/- to host phy.
> > >>  - If USB ID's GPIO level is high, by standard, the OTG port is
> > >>    configured for device role by not sourcing VBUS and switching D+/- to
> > >>    device controller.
> > >
> > > IMO it's not very elegant to handle VBUS power on/off in extcon driver.
> > > Creating fixed regulator would allow to make VBUS handling more generic.
> 
> I agree. But please, see below.
> 
> > 
> > IMHO it's just layers of abstraction piled on top of each other here.
> > 
> > I would put this adjacent to the phy driver somewhere in drivers/usb/*
> > and make the actual USB-driver thing handle its GPIOs directly.
> > But I guess David and Felipe have already discussed that as we're
> > seeing this patch?
> 
> Felipe suggested to "divide to conquer" instead of having a single
> extcon driver to handle all these functions:
> 
> - The mux functions would be controlled by a possible new pinctrl-gpio
> driver (Linus, your input here would be nice :)
> - The VBUS would be a fixed regulator
> - The USB ID would make usage of existent extcon-gpio
> 
> But the on fw side, this is a single ACPI device representing a virtual
> device for USB OTG port, which is nothing but a bunch of independent
> GPIOs.
> 
> I could make a mfd driver to register devices for those simpler and more
> generic drivers, but according to [1] community recognized it as a hack
> with ACPI since I'd need to give them the GPIO without requesting on
> mfd.
> 
> I'm open for suggestions :)

use MFD to create children devices and pass the required data to each
one ?

-- 
balbi

Download attachment "signature.asc" of type "application/pgp-signature" (820 bytes)