linux-kernel - RE: [PATCH v7 10/14] usb: otg: add hcd companion support

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 for Android: free password hash cracker in your pocket

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

Date:	Thu, 12 May 2016 14:16:38 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
cc:	Roger Quadros <rogerq@...com>, Rob Herring <robh@...nel.org>,
	"peter.chen@...escale.com" <peter.chen@...escale.com>,
	"balbi@...nel.org" <balbi@...nel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"jun.li@...escale.com" <jun.li@...escale.com>,
	"mathias.nyman@...ux.intel.com" <mathias.nyman@...ux.intel.com>,
	"tony@...mide.com" <tony@...mide.com>,
	"Joao.Pinto@...opsys.com" <Joao.Pinto@...opsys.com>,
	"abrestic@...omium.org" <abrestic@...omium.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: RE: [PATCH v7 10/14] usb: otg: add hcd companion support

On Thu, 12 May 2016, Yoshihiro Shimoda wrote:

> > > Alan, does USB core even know which EHCI and OHCI are linked to the same port
> > > or the handoff is software transparent?
> > 
> > The core knows.  It doesn't use the information for a whole lot of
> > things, but it does use it in a couple of places.  Search for
> > "companion" in core/hcd-pci.c and you'll see.
> 
> Thank you for the information. I didn't know this code.
> If my understanding is correct, the core/hcd-pci.c code will not be used by non-PCI devices.
> In other words, nobody sets "hcd->self.hs_companion" if we use such a device.

That's right.

> So, I will try to add such a code if needed.

The main thing to watch out for is during system resume.  The EHCI
controller must not be resumed until all of its companion controllers
have been resumed.

Alan Stern