iommu: Add sysfs support for IOMMUs

IOMMUs currently have no common representation to userspace, most
seem to have no representation at all aside from a few printks
on bootup.  There are however features of IOMMUs that are useful
to know about.  For instance the IOMMU might support superpages,
making use of processor large/huge pages more important in a device
assignment scenario.  It's also useful to create cross links between
devices and IOMMU hardware units, so that users might be able to
load balance their devices to avoid thrashing a single hardware unit.

This patch adds a device create and destroy interface as well as
device linking, making it very lightweight for an IOMMU driver to add
basic support.  IOMMU drivers can provide additional attributes
automatically by using an attribute_group.

The attributes exposed are expected to be relatively device specific,
the means to retrieve them certainly are, so there are currently no
common attributes for the new class created here.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

1 files changed, 26 insertions, 0 deletions

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index a2e5843b0a22..7fd16e3d1f25 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -187,6 +187,12 @@ extern int iommu_domain_get_attr(struct iommu_domain *domain, enum iommu_attr,
 				 void *data);
 extern int iommu_domain_set_attr(struct iommu_domain *domain, enum iommu_attr,
 				 void *data);
+struct device *iommu_device_create(struct device *parent, void *drvdata,
+				   const struct attribute_group **groups,
+				   const char *fmt, ...);
+void iommu_device_destroy(struct device *dev);
+int iommu_device_link(struct device *dev, struct device *link);
+void iommu_device_unlink(struct device *dev, struct device *link);
 
 /* Window handling function prototypes */
 extern int iommu_domain_window_enable(struct iommu_domain *domain, u32 wnd_nr,
@@ -397,6 +403,26 @@ static inline int iommu_domain_set_attr(struct iommu_domain *domain,
 	return -EINVAL;
 }
 
+struct device *iommu_device_create(struct device *parent, void *drvdata,
+				   const struct attribute_group **groups,
+				   const char *fmt, ...)
+{
+	return ERR_PTR(-ENODEV);
+}
+
+void iommu_device_destroy(struct device *dev)
+{
+}
+
+int iommu_device_link(struct device *dev, struct device *link)
+{
+	return -EINVAL;
+}
+
+void iommu_device_unlink(struct device *dev, struct device *link)
+{
+}
+
 #endif /* CONFIG_IOMMU_API */
 
 #endif /* __LINUX_IOMMU_H */