From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH v6 1/8] iommu: provide early initialisation hook for IOMMU drivers Date: Wed, 03 Dec 2014 20:57:50 +0100 Message-ID: <2579924.PPXuLn3o19@wuerfel> References: <1417453034-21379-1-git-send-email-will.deacon@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: 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: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org Cc: jroedel-l3A5Bk7waGM@public.gmane.org, Will Deacon , Pantelis Antoniou , Linux IOMMU , Thierry Reding , Rob Herring , Laurent Pinchart , Grant Likely , Varun Sethi , David Woodhouse List-Id: iommu@lists.linux-foundation.org On Tuesday 02 December 2014 14:16:57 Grant Likely wrote: > On Mon, Dec 1, 2014 at 11:54 PM, Rob Herring wrote: > > On Mon, Dec 1, 2014 at 10:57 AM, Will Deacon wrote: > >> > >> +static inline void of_iommu_set_ops(struct device_node *np, > >> + const struct iommu_ops *ops) > >> +{ > >> + np->data = (struct iommu_ops *)ops; > >> +} > >> + > >> +static inline struct iommu_ops *of_iommu_get_ops(struct device_node *np) > >> +{ > >> + return np->data; > >> +} > > > > This may collide with other users. While use of it is rare, PPC uses > > it in its PCI code. The OF_DYNAMIC code frees it but never actually > > sets it. There may be some coming usage with the DT overlay code or > > that's just a bug. Pantelis or Grant can comment. If not, I think we > > really should try to get rid of this pointer rather than expand it's > > usage. > > > > I didn't see a user of this. I'm guessing that is coming in a SMMU patch? > > Good catch. This is not good. The data pointer should be avoided since > there are no controls over its use. Until a better solution can be > implemented, probably the safest thing to do is add a struct iommu_ops > pointer to struct device_node. However, assuming that only a small > portion of nodes will actually have iommu_ops set, I'd rather see a > separate registry that matches device_nodes to iommu_ops. Fair enough. Will, can you take a copy of drivers/dma/of-dma.c and adapt it as needed? It should be exactly what we need to start out and can be extended and generalized later. ARnd From mboxrd@z Thu Jan 1 00:00:00 1970 From: arnd@arndb.de (Arnd Bergmann) Date: Wed, 03 Dec 2014 20:57:50 +0100 Subject: [PATCH v6 1/8] iommu: provide early initialisation hook for IOMMU drivers In-Reply-To: References: <1417453034-21379-1-git-send-email-will.deacon@arm.com> Message-ID: <2579924.PPXuLn3o19@wuerfel> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tuesday 02 December 2014 14:16:57 Grant Likely wrote: > On Mon, Dec 1, 2014 at 11:54 PM, Rob Herring wrote: > > On Mon, Dec 1, 2014 at 10:57 AM, Will Deacon wrote: > >> > >> +static inline void of_iommu_set_ops(struct device_node *np, > >> + const struct iommu_ops *ops) > >> +{ > >> + np->data = (struct iommu_ops *)ops; > >> +} > >> + > >> +static inline struct iommu_ops *of_iommu_get_ops(struct device_node *np) > >> +{ > >> + return np->data; > >> +} > > > > This may collide with other users. While use of it is rare, PPC uses > > it in its PCI code. The OF_DYNAMIC code frees it but never actually > > sets it. There may be some coming usage with the DT overlay code or > > that's just a bug. Pantelis or Grant can comment. If not, I think we > > really should try to get rid of this pointer rather than expand it's > > usage. > > > > I didn't see a user of this. I'm guessing that is coming in a SMMU patch? > > Good catch. This is not good. The data pointer should be avoided since > there are no controls over its use. Until a better solution can be > implemented, probably the safest thing to do is add a struct iommu_ops > pointer to struct device_node. However, assuming that only a small > portion of nodes will actually have iommu_ops set, I'd rather see a > separate registry that matches device_nodes to iommu_ops. Fair enough. Will, can you take a copy of drivers/dma/of-dma.c and adapt it as needed? It should be exactly what we need to start out and can be extended and generalized later. ARnd