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From:   Logan Gunthorpe <logang@deltatee.com>
To:     linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
        linux-block@vger.kernel.org, linux-pci@vger.kernel.org,
        linux-mm@kvack.org, iommu@lists.linux-foundation.org
Cc:     Stephen Bates <sbates@raithlin.com>,
        Christoph Hellwig <hch@lst.de>,
        Dan Williams <dan.j.williams@intel.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@amd.com>,
        Ira Weiny <iweiny@intel.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Don Dutile <ddutile@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Logan Gunthorpe <logang@deltatee.com>
Date:   Fri,  6 Nov 2020 10:00:27 -0700
Message-Id: <20201106170036.18713-7-logang@deltatee.com>
In-Reply-To: <20201106170036.18713-1-logang@deltatee.com>
References: <20201106170036.18713-1-logang@deltatee.com>
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Subject: [RFC PATCH 06/15] dma-mapping: Add flags to dma_map_ops to indicate PCI P2PDMA support
Precedence: bulk

Add a flags member to the dma_map_ops structure with one flag to
indicate support for PCI P2PDMA.

Also, add a helper to check if a device supports PCI P2PDMA.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
 include/linux/dma-map-ops.h | 3 +++
 include/linux/dma-mapping.h | 5 +++++
 kernel/dma/mapping.c        | 8 ++++++++
 3 files changed, 16 insertions(+)

diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index a5f89fc4d6df..8c12dfa43ce1 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -12,6 +12,9 @@
 struct cma;
 
 struct dma_map_ops {
+	unsigned int flags;
+#define DMA_F_PCI_P2PDMA_SUPPORTED     (1 << 0)
+
 	void *(*alloc)(struct device *dev, size_t size,
 			dma_addr_t *dma_handle, gfp_t gfp,
 			unsigned long attrs);
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 8d028e15b531..3646c6ba6a00 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -149,6 +149,7 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
 		unsigned long attrs);
 bool dma_can_mmap(struct device *dev);
 int dma_supported(struct device *dev, u64 mask);
+int dma_pci_p2pdma_supported(struct device *dev);
 int dma_set_mask(struct device *dev, u64 mask);
 int dma_set_coherent_mask(struct device *dev, u64 mask);
 u64 dma_get_required_mask(struct device *dev);
@@ -244,6 +245,10 @@ static inline int dma_supported(struct device *dev, u64 mask)
 {
 	return 0;
 }
+static inline int dma_pci_p2pdma_supported(struct device *dev)
+{
+	return 0;
+}
 static inline int dma_set_mask(struct device *dev, u64 mask)
 {
 	return -EIO;
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 51bb8fa8eb89..192418ef43f8 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -567,6 +567,14 @@ int dma_supported(struct device *dev, u64 mask)
 }
 EXPORT_SYMBOL(dma_supported);
 
+int dma_pci_p2pdma_supported(struct device *dev)
+{
+	const struct dma_map_ops *ops = get_dma_ops(dev);
+
+	return !ops || ops->flags & DMA_F_PCI_P2PDMA_SUPPORTED;
+}
+EXPORT_SYMBOL(dma_pci_p2pdma_supported);
+
 #ifdef CONFIG_ARCH_HAS_DMA_SET_MASK
 void arch_dma_set_mask(struct device *dev, u64 mask);
 #else
-- 
2.20.1