From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [RFC PATCH 1/2] dt-bindings: pci: Add drop mask property for MSI and IOMMU Date: Fri, 7 Jul 2017 16:42:48 +0100 Message-ID: References: <1499411399-25103-1-git-send-email-srinath.mannam@broadcom.com> <1499411399-25103-2-git-send-email-srinath.mannam@broadcom.com> <20170707133052.GB3425@leverpostej> <89f871d1-fc28-aa0b-2460-cf834e7e99f6@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Scott Branden , Mark Rutland , Srinath Mannam Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Rob Herring , bcm-kernel-feedback-list-dY08KVG/lbpWk0Htik3J/w@public.gmane.org, Bjorn Helgaas , Frank Rowand List-Id: devicetree@vger.kernel.org On 07/07/17 16:22, Scott Branden wrote: > Hi Robin, > > On 17-07-07 07:55 AM, Robin Murphy wrote: >> On 07/07/17 14:30, Mark Rutland wrote: [...] >>> Your mapping can be expressed today using a number of msi-map entries, >>> which you can easily generate programmatically with a trivial perl >>> script, without requiring a new binding or any new kernel code. >>> >>> Please do that instead. >> Indeed. The systems I'm aware of which need to express non-trivial RID >> to SID mappings tend to have the bootloader probe PCI and dynamically >> generate map entries per discovered RID, but even if you wanted to >> statically generate the whole lot for the worst-case bus range that's >> still only 512 entries, which is not unmanageable. Notably, it's also >> what would have to be done (in equivalent) for IORT, although I assume >> this is an embedded platform for which nobody cares about ACPI. > Actually we will care about ACPI and need to add it (doesn't need to be > in this patchet unless easy to do so...) Ah, OK, that's an even stronger argument for not adding anything new then - DT "iommu-map" is already marginally more expressive than IORT ID mappings can be, so there doesn't seem to be much justification for diverging them further. Robin.