From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH v5 p2 16/19] tools/libxl: arm: Use an higher value for the GIC phandle Date: Thu, 09 Apr 2015 17:33:49 +0100 Message-ID: <5526A9ED.2000803@gmail.com> References: <1428592185-18581-1-git-send-email-julien.grall@citrix.com> <1428592185-18581-17-git-send-email-julien.grall@citrix.com> <21798.42495.633318.607315@mariner.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YgFPI-0004oK-8o for xen-devel@lists.xenproject.org; Thu, 09 Apr 2015 16:34:20 +0000 Received: by wiaa2 with SMTP id a2so105405620wia.0 for ; Thu, 09 Apr 2015 09:34:16 -0700 (PDT) In-Reply-To: <21798.42495.633318.607315@mariner.uk.xensource.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: Ian Jackson , Julien Grall Cc: Wei Liu , ian.campbell@citrix.com, Julien Grall , tim@xen.org, stefano.stabellini@citrix.com, xen-devel@lists.xenproject.org List-Id: xen-devel@lists.xenproject.org Hi Ian, On 09/04/15 17:17, Ian Jackson wrote: > Julien Grall writes ("[PATCH v5 p2 16/19] tools/libxl: arm: Use an higher value for the GIC phandle"): >> The partial device tree may contains phandle. The Device Tree Compiler >> tends to allocate the phandle from 1. > > I have to say I have no idea what a phandle is... A phandle is a way to reference another node in the device tree. Any node that can referenced defines a phandle property with a unique unsigned 32 bit value. >> Reserve the ID 65000 for the GIC phandle. I think we can safely assume >> that the partial device tree will never contain a such ID. > > Do we control the DT compiler ? What if it should change its > phandle allocation algorithm ? We don't control the DT compiler. But the algorithm of the phandle will unlikely change. FWIW, the compiler is very tiny, it's not GCC. I only expect people using the partial device tree in very specific use case. Generic use case is not even possible with the current status of non-PCI (i.e device tree) passthrough. So people control their environment. As I said later in patch, supporting dynamic allocation will require some rework in the device tree creation for the guest. So I was suggesting this solution as temporary in order to not block the DT passthrough. >> +/* >> + * The device tree compiler (DTC) is allocating the phandle from 1 to >> + * onwards. Reserve a high value for the GIC phandle. >> + */ > > FYI this should read "The device tree compiler (DTC) allocates phandle > values frrom 1 onwards". Thanks, I will update the comment. Regards, -- Julien Grall