[PATCH v5 01/14] drivers: iommu: add FWNODE_IOMMU fwnode type

On Thursday, September 29, 2016 03:15:20 PM Lorenzo Pieralisi wrote:

Hi Rafael,

On Fri, Sep 09, 2016 at 03:23:30PM +0100, Lorenzo Pieralisi wrote:

quoted

On systems booting with a device tree, every struct device is
associated with a struct device_node, that represents its DT
representation. The device node can be used in generic kernel
contexts (eg IRQ translation, IOMMU streamid mapping), to
retrieve the properties associated with the device and carry
out kernel operation accordingly. Owing to the 1:1 relationship
between the device and its device_node, the device_node can also
be used as a look-up token for the device (eg looking up a device
through its device_node), to retrieve the device in kernel paths
where the device_node is available.

On systems booting with ACPI, the same abstraction provided by
the device_node is required to provide look-up functionality.

Therefore, mirroring the approach implemented in the IRQ domain
kernel layer, this patch adds an additional fwnode type FWNODE_IOMMU.

This patch also implements a glue kernel layer that allows to
allocate/free FWNODE_IOMMU fwnode_handle structures and associate
them with IOMMU devices.

Signed-off-by: Lorenzo Pieralisi <redacted>
Reviewed-by: Hanjun Guo <redacted>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: "Rafael J. Wysocki" <redacted>
---
 include/linux/fwnode.h |  1 +
 include/linux/iommu.h  | 25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h
index 8516717..6e10050 100644
--- a/include/linux/fwnode.h
+++ b/include/linux/fwnode.h

@@ -19,6 +19,7 @@ enum fwnode_type {
 	FWNODE_ACPI_DATA,
 	FWNODE_PDATA,
 	FWNODE_IRQCHIP,
+	FWNODE_IOMMU,

This patch provides groundwork for this series and it is key for
the rest of it, basically the point here is that we need a fwnode
to differentiate platform devices created out of static ACPI tables
entries (ie IORT), that represent IOMMU components.

The corresponding device is not an ACPI device (I could fabricate one as
it is done for other static tables entries eg FADT power button, but I
do not necessarily see the reason for doing that given that all we need
the fwnode for is a token identifier), so FWNODE_ACPI does not apply
here.

Please let me know if it is reasonable how I sorted this out (it
is basically identical to IRQCHIP, just another enum entry), the
remainder of the code depends on this.

I'm not familiar with the use case, so I don't see anything unreasonable
in it.

If you're asking about whether or not I mind adding more fwnode types in
principle, then no, I don't. :-) 

Thanks,
Rafael