linux-kernel - [RFC PATCH 2/5] drivers/base: add a function to test peer to peer capability

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Date:   Tue, 29 Jan 2019 12:47:25 -0500
From:   jglisse@...hat.com
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org,
        Jérôme Glisse <jglisse@...hat.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Christian Koenig <christian.koenig@....com>,
        Felix Kuehling <Felix.Kuehling@....com>,
        Jason Gunthorpe <jgg@...lanox.com>, linux-pci@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <jroedel@...e.de>,
        iommu@...ts.linux-foundation.org
Subject: [RFC PATCH 2/5] drivers/base: add a function to test peer to peer capability

From: Jérôme Glisse <jglisse@...hat.com>

device_test_p2p() return true if two devices can peer to peer to
each other. We add a generic function as different inter-connect
can support peer to peer and we want to genericaly test this no
matter what the inter-connect might be. However this version only
support PCIE for now.

Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
Cc: Logan Gunthorpe <logang@...tatee.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Rafael J. Wysocki <rafael@...nel.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Christian Koenig <christian.koenig@....com>
Cc: Felix Kuehling <Felix.Kuehling@....com>
Cc: Jason Gunthorpe <jgg@...lanox.com>
Cc: linux-kernel@...r.kernel.org
Cc: linux-pci@...r.kernel.org
Cc: dri-devel@...ts.freedesktop.org
Cc: Christoph Hellwig <hch@....de>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Robin Murphy <robin.murphy@....com>
Cc: Joerg Roedel <jroedel@...e.de>
Cc: iommu@...ts.linux-foundation.org
---
 drivers/base/core.c    | 20 ++++++++++++++++++++
 include/linux/device.h |  1 +
 2 files changed, 21 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 0073b09bb99f..56023b00e108 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -26,6 +26,7 @@
 #include <linux/netdevice.h>
 #include <linux/sched/signal.h>
 #include <linux/sysfs.h>
+#include <linux/pci-p2pdma.h>
 
 #include "base.h"
 #include "power/power.h"
@@ -3167,3 +3168,22 @@ void device_set_of_node_from_dev(struct device *dev, const struct device *dev2)
 	dev->of_node_reused = true;
 }
 EXPORT_SYMBOL_GPL(device_set_of_node_from_dev);
+
+/**
+ * device_test_p2p - test if two device can peer to peer to each other
+ * @devA: device A
+ * @devB: device B
+ * Returns: true if device can peer to peer to each other, false otherwise
+ */
+bool device_test_p2p(struct device *devA, struct device *devB)
+{
+	/*
+	 * For now we only support PCIE peer to peer but other inter-connect
+	 * can be added.
+	 */
+	if (pci_test_p2p(devA, devB))
+		return true;
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(device_test_p2p);
diff --git a/include/linux/device.h b/include/linux/device.h
index 6cb4640b6160..0d532d7f0779 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1250,6 +1250,7 @@ extern int device_online(struct device *dev);
 extern void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode);
 extern void set_secondary_fwnode(struct device *dev, struct fwnode_handle *fwnode);
 void device_set_of_node_from_dev(struct device *dev, const struct device *dev2);
+bool device_test_p2p(struct device *devA, struct device *devB);
 
 static inline int dev_num_vf(struct device *dev)
 {
-- 
2.17.2