From: Greg KH <greg@kroah.com>
To: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
andy.green@linaro.org, Linux USB list <linux-usb@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>
Subject: Re: RFC: Platform data for onboard USB assets
Date: Fri, 11 Mar 2011 08:56:42 -0800 [thread overview]
Message-ID: <20110311165642.GA9996@kroah.com> (raw)
In-Reply-To: <20110311164850.GT1760@opensource.wolfsonmicro.com>
On Fri, Mar 11, 2011 at 04:48:50PM +0000, Mark Brown wrote:
> On Fri, Mar 11, 2011 at 08:35:22AM -0800, Greg KH wrote:
> > On Fri, Mar 11, 2011 at 04:27:59PM +0000, Mark Brown wrote:
>
> > > I'm actually not that fussed about the MAC address use case itself and
> > > do tend to agree with you that that's handlable in userspace but for the
> > > other things that might need to be configured there's a lot of things
> > > that for non-discoverable buses we're currently passing through platform
> > > data so switching to bouncing things through userspace would itself be a
> > > substantial change from other systems.
>
> > But USB _is_ discoverable, that's my point.
>
> USB itself is discoverable but the when the USB bus you're looking at is
> one that's soldered down onto a board in a specific design all bets are
> off regarding how complete the information you get will be. On a basic
> level the designers may have done things like omit the configuration
> EEPROMs that would set the device IDs that the driver should be relying
> on to identify the hardware configuration. There may be other, nastier,
> things going on.
Then you use the existing platform data for your USB host controller
driver. Doesn't that work today just fine?
> > > You can't in general rely on the system being neatly abstracted and
> > > while discoverable buses do avoid many problems in this sort of area
> > > there are still things which can only be discovered through reference to
> > > the schematics or similar, especially if you care about the microamps.
>
> > Again, that's not USB, so it isn't relevant here.
>
> You really can't make this assumption about discoverable buses on
> embedded devices. The discoverability will get you most of the way
> there but not always all of the way there.
Then the bus is not really USB, sorry. USB is discoverable, _and_ can
support enumeration in non-deterministic ways. If people are using it
in other ways then it is not USB and is something else.
thanks,
greg k-h
next prev parent reply other threads:[~2011-03-11 16:57 UTC|newest]
Thread overview: 156+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-11 9:50 RFC: Platform data for onboard USB assets Andy Green
2011-03-11 12:31 ` Arnd Bergmann
2011-03-11 12:44 ` Andy Green
2011-03-11 14:42 ` Roger Quadros
2011-03-11 15:12 ` Roger Quadros
2011-03-11 15:22 ` Arnd Bergmann
2011-03-11 15:50 ` Roger Quadros
2011-03-11 15:55 ` Arnd Bergmann
2011-03-11 15:29 ` Mark Brown
2011-03-11 15:54 ` Arnd Bergmann
2011-03-11 16:03 ` Mark Brown
2011-03-11 16:14 ` Greg KH
2011-03-11 16:27 ` Mark Brown
2011-03-11 16:35 ` Greg KH
2011-03-11 16:48 ` Mark Brown
2011-03-11 16:56 ` Greg KH [this message]
2011-03-11 17:08 ` Mark Brown
2011-03-11 17:23 ` Greg KH
2011-03-11 17:41 ` Mark Brown
2011-03-17 2:14 ` Nicolas Pitre
2011-03-17 20:13 ` Greg KH
2011-03-17 20:18 ` Mark Brown
2011-03-17 20:26 ` Greg KH
2011-03-17 21:24 ` Mark Brown
2011-03-17 21:31 ` Greg KH
2011-03-17 21:40 ` Mark Brown
2011-03-17 21:47 ` Greg KH
2011-03-17 22:33 ` Arnd Bergmann
2011-03-17 22:53 ` Greg KH
2011-03-17 23:18 ` Andy Green
2011-03-17 23:25 ` Greg KH
2011-03-18 7:42 ` Andy Green
2011-03-18 22:54 ` Benjamin Herrenschmidt
2011-03-18 22:57 ` Andy Green
2011-03-18 4:54 ` Grant Likely
2011-03-18 8:19 ` Arnd Bergmann
2011-03-17 23:22 ` Andy Green
2011-03-18 15:00 ` Arnd Bergmann
2011-03-18 15:15 ` Mark Brown
2011-03-18 17:52 ` Andy Green
2011-03-18 18:20 ` David Anders
2011-03-18 18:25 ` Mark Brown
2011-03-18 20:02 ` Andy Green
2011-03-18 21:11 ` Arnd Bergmann
2011-03-18 21:17 ` Andy Green
2011-03-18 20:06 ` Arnd Bergmann
2011-03-18 21:33 ` Andy Green
2011-03-18 23:25 ` Mark Brown
2011-03-18 23:33 ` Andy Green
2011-03-18 21:36 ` Grant Likely
2011-03-18 22:47 ` Benjamin Herrenschmidt
2011-03-18 21:28 ` Grant Likely
2011-03-18 23:04 ` Andy Green
2011-03-18 22:37 ` Benjamin Herrenschmidt
2011-03-18 22:39 ` Andy Green
2011-03-17 23:27 ` Grant Likely
2011-03-18 7:49 ` Andy Green
2011-03-18 8:25 ` Arnd Bergmann
2011-03-18 8:38 ` Andy Green
2011-03-17 22:11 ` Arnd Bergmann
2011-03-17 22:20 ` Greg KH
2011-03-18 8:42 ` Roger Quadros
2011-03-18 9:01 ` Arnd Bergmann
2011-03-18 9:55 ` Roger Quadros
2011-03-18 10:09 ` Andy Green
2011-03-17 21:03 ` Nicolas Pitre
2011-03-17 21:32 ` Greg KH
2011-03-11 16:26 ` Andy Green
2011-03-11 16:45 ` Alan Stern
2011-03-11 16:51 ` Andy Green
2011-03-11 17:08 ` Greg KH
2011-03-11 18:09 ` Andy Green
2011-03-11 19:12 ` Alan Stern
2011-03-11 20:05 ` Andy Green
2011-03-11 20:21 ` Greg KH
2011-03-11 21:07 ` Andy Green
2011-03-11 21:44 ` Greg KH
2011-03-11 22:24 ` Andy Green
2011-03-12 16:00 ` Alan Stern
2011-03-12 23:02 ` Andy Green
2011-03-11 19:37 ` Greg KH
2011-03-11 16:53 ` Mark Brown
2011-03-11 16:08 ` Greg KH
2011-03-11 16:20 ` Andy Green
2011-03-11 16:36 ` Greg KH
2011-03-11 16:41 ` Andy Green
2011-03-11 22:07 ` Benjamin Herrenschmidt
2011-03-11 21:52 ` Benjamin Herrenschmidt
2011-03-11 22:45 ` Grant Likely
2011-03-11 22:47 ` Andy Green
2011-03-11 23:39 ` Grant Likely
2011-03-14 14:54 ` Arnd Bergmann
2011-03-22 15:05 ` Jaswinder Singh
2011-03-22 16:04 ` Andy Green
2011-03-22 18:19 ` Jaswinder Singh
2011-03-22 18:37 ` Andy Green
2011-03-22 18:59 ` Jaswinder Singh
2011-03-22 19:35 ` Andy Green
[not found] ` <AANLkTim=ezye=1fQP_1a2SWbPnbENP9B+k27Z3AkS=zf@mail.gmail.com>
2011-03-22 15:12 ` Mark Brown
2011-03-22 15:23 ` Jaswinder Singh
2011-03-24 18:56 ` Grant Likely
2011-03-22 21:08 ` Benjamin Herrenschmidt
2011-03-22 22:37 ` Andy Green
2011-03-23 1:03 ` Benjamin Herrenschmidt
2011-03-23 2:26 ` Nicolas Pitre
2011-03-23 3:23 ` Benjamin Herrenschmidt
2011-03-23 4:21 ` Nicolas Pitre
2011-03-23 4:56 ` Greg KH
2011-03-23 5:44 ` Benjamin Herrenschmidt
2011-03-23 9:38 ` Alan Cox
2011-03-23 10:53 ` Mark Brown
2011-03-23 15:04 ` Greg KH
2011-03-23 15:10 ` Mark Brown
2011-03-23 15:24 ` Andy Green
2011-03-23 15:45 ` Arnd Bergmann
2011-03-23 15:38 ` Nicolas Pitre
2011-03-23 9:31 ` Andy Green
2011-03-23 9:47 ` Alan Cox
2011-03-23 10:06 ` Andy Green
2011-03-23 10:32 ` Arnd Bergmann
2011-03-23 10:39 ` Andy Green
2011-03-23 10:56 ` Alan Cox
2011-03-23 11:13 ` Andy Green
2011-03-23 11:34 ` Alan Cox
2011-03-23 12:02 ` Andy Green
2011-03-23 15:08 ` Greg KH
2011-03-23 16:12 ` Arnd Bergmann
2011-03-23 16:22 ` Greg KH
2011-03-23 16:34 ` Andy Green
2011-03-23 16:56 ` [RFC] usbnet: use eth%d name for known ethernet devices Arnd Bergmann
2011-03-23 17:04 ` Andy Green
2011-03-23 17:11 ` Arnd Bergmann
2011-03-24 10:45 ` Andy Green
2011-03-23 17:13 ` Arnd Bergmann
2011-03-23 17:54 ` David Anders
2011-03-23 18:46 ` Greg KH
2011-03-23 19:35 ` Arnd Bergmann
[not found] ` <AANLkTim7hPfTv3gDYnh+jGxHBg0OvX=r1FKYoHnH7H_o@mail.gmail.com>
2011-03-23 19:57 ` Arnd Bergmann
2011-03-23 19:59 ` Randy Dunlap
2011-03-23 23:17 ` Michal Nazarewicz
2011-03-23 23:19 ` Randy Dunlap
2011-03-23 23:38 ` Steve Calfee
2011-03-24 0:01 ` Ben Hutchings
2011-03-24 13:13 ` Arnd Bergmann
2011-03-24 13:15 ` Arnd Bergmann
2011-03-24 13:44 ` Andy Green
2011-03-24 13:56 ` Alan Stern
2011-03-24 17:20 ` Alexey Orishko
2011-03-25 11:57 ` Arnd Bergmann
2011-03-25 16:26 ` Alexey Orishko
2011-03-25 16:43 ` Arnd Bergmann
2011-03-24 19:17 ` RFC: Platform data for onboard USB assets Grant Likely
2011-03-24 20:10 ` Andy Green
2011-03-23 14:55 ` Nicolas Pitre
2011-03-23 10:22 ` Benjamin Herrenschmidt
2011-03-23 15:11 ` Nicolas Pitre
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