linux-kernel - Re: [linux-usb-devel] [PATCH] : Allow embedded developers USB options normally reserved for OTG

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Date:	Thu, 3 Jan 2008 11:47:19 +0800
From:	"Bryan Wu" <cooloney.lkml@...il.com>
To:	"David Brownell" <david-b@...bell.net>
Cc:	linux-usb-devel@...ts.sourceforge.net,
	"Robin Getz" <rgetz@...ckfin.uclinux.org>, gregkh@...e.de,
	linux-kernel@...r.kernel.org
Subject: Re: [linux-usb-devel] [PATCH] : Allow embedded developers USB options normally reserved for OTG

On Jan 3, 2008 2:47 AM, David Brownell <david-b@...bell.net> wrote:
> On Wednesday 02 January 2008, Robin Getz wrote:
> > From: Robin Getz <rgetz@...ckfin.uclinux.org>
> >
> > Allow embedded developers to turn support for USB Hubs off even if they have a
> > full root hub. This saves the overhead (RAM and Flash size).
>
> ISTR that it won't save very much code though ... the Linux USB
> stack structures all its enumeration logic around hubs.
>
>
> > Allow embedded developers the capabilities of the "otg_whitelist.h" - a
> > product whitelist, so USB peripherals not listed there will be rejected
> > during enumeration. This is the desired operation for many embedded products.
> >
> > Signed-off-by: Robin Getz <rgetz@...ckfin.uclinux.org>
>
> This is probably the right thing to do.  Correct me if I'm wrong,
> but USB-IF recently put out some specs about "embedded hosts" which
> basically boil down to saying you can adopt the same functionality
> restrictions that used to be OTG-only.  Which is why now there are
> embedded developers who'd like this option.  :)
>
> - Dave
>
>

Yes, "embedded hosts" which currently not support whole USB 2.0 spec
is what Robin's patch serving for.

Although in MUSB of Blackfin can support USB_OTG and we can enable
this, some real embedded application just use the MUSB_HOST mode. So
just enable MUSB_HOST  can save some embedded space because it does
not including MUSB_PERIPHERAL code.

I believe some embedded SoC including embedded USB host controller
also need this option open for them.

Thanks
-Bryan Wu
>
>
> >
> > ---
> >
> >  drivers/usb/core/Kconfig |    7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> >
> > Index: linux-2.6.x/drivers/usb/core/Kconfig
> > ===================================================================
> > --- linux-2.6.x/drivers/usb/core/Kconfig      (revision 4074)
> > +++ linux-2.6.x/drivers/usb/core/Kconfig      (working copy)
> > @@ -95,8 +95,9 @@
> >
> >  config USB_OTG_WHITELIST
> >       bool "Rely on OTG Targeted Peripherals List"
> > -     depends on USB_OTG
> > -     default y
> > +     depends on USB_OTG || EMBEDDED
> > +     default y if USB_OTG
> > +     default n if EMBEDDED
> >       help
> >         If you say Y here, the "otg_whitelist.h" file will be used as a
> >         product whitelist, so USB peripherals not listed there will be
> > @@ -111,7 +112,7 @@
> >
> >  config USB_OTG_BLACKLIST_HUB
> >       bool "Disable external hubs"
> > -     depends on USB_OTG
> > +     depends on USB_OTG || EMBEDDED
> >       help
> >         If you say Y here, then Linux will refuse to enumerate
> >         external hubs.  OTG hosts are allowed to reduce hardware
> >
> --
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