linux-kernel - Re: [PATCH v2 4/4] usb: Add APIs to access host registers from Tegra PHY

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]

Message-ID: <20130117153229.GA21904@arwen.pp.htv.fi>
Date:	Thu, 17 Jan 2013 17:32:29 +0200
From:	Felipe Balbi <balbi@...com>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Felipe Balbi <balbi@...com>,
	Venu Byravarasu <vbyravarasu@...dia.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v2 4/4] usb: Add APIs to access host registers from Tegra
 PHY

On Thu, Jan 17, 2013 at 10:21:53AM -0500, Alan Stern wrote:
> On Thu, 17 Jan 2013, Felipe Balbi wrote:
> 
> > > Bits 31 & 30 from PORTSC register were allocated by our SOC designers
> > > to inform the host controller about the PHY type to be used. 
> > 
> > Wow, that's something you should never do. PORTSC register belongs to
> > the EHCI controller and those bits are reserved for future use and they
> > *MUST* return zero. I wouldn't be surprised if current EHCI driver
> > assumes those bits will be zero and/or makes sure they're set to zero
> > when writing to PORTSC register.
> 
> In fact, those bits _have_ been assigned an official purpose in the 
> EHCI-1.1 addendum.  Presumably the Tegra hardware only supports 
> EHCI-1.0.

I see, they're used for device addresses now.

How can we make sure on Tegra systems we won't use those top two bits ?

-- 
balbi

Download attachment "signature.asc" of type "application/pgp-signature" (837 bytes)