From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [PATCH RFC 3/9] console: add EHCI debug port based serial console Date: Tue, 31 Jul 2012 13:21:14 -0400 Message-ID: <20120731172114.GB29533@phenom.dumpdata.com> References: <4FBE4DA50200007800085E16@nat28.tlf.novell.com> <20120730205133.GN4547@phenom.dumpdata.com> <5017A101020000780009174E@nat28.tlf.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <5017A101020000780009174E@nat28.tlf.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: xen-devel List-Id: xen-devel@lists.xenproject.org On Tue, Jul 31, 2012 at 08:10:25AM +0100, Jan Beulich wrote: > >>> On 30.07.12 at 22:51, Konrad Rzeszutek Wilk wrote: > >> + set_fixmap_nocache(FIX_EHCI_DBGP, dbgp->bar_val); > > > > Should this have dbgp->bar_val & PAGE_MASK ? > > No, the set_fixmap_nocache() implementation shifts out the low > bits. > > >> + case PHYSDEVOP_DBGP_RESET_PREPARE: > > > > Oh, you have a handoff protocol! > > > > So how does this work without using this? Meaning if one uses Xen hypervisor > > EHCI with a pvops kernel that does not implement this? > > The hypervisor will lose access to its console (and the next console > access will cause a brief hang that does no other harm). That's the > same behavior as for native Linux if you ripped out the handoff > protocol (and the effect is even specified that way by the > specification). Plus - no-one is required to use the new functionality > when (s)he's aware that Dom0 doesn't cope. Sure. > > >> + return ehci_dbgp_external_startup(&ehci_dbgp) ?: 1; > > > > Oh, this is new. With the ?: it just passes on the return value from > > ehci_dbgp_external_startup? > > Yes, but it's not new. Just grep for the construct in Xen or Linux - > it's being used in a number of places, and has been supported by > gcc virtually forever. Ok, never hit upon it until now. Either way, you can tag on Reviewed-by: Konrad Rzeszutek Wilk if you would like. Thanks! > > Jan