On 28 July 2015 at 15:39, Rob Herring [off-list ref] wrote:

On Tue, Jul 28, 2015 at 8:19 AM, Tomeu Vizoso
[off-list ref] wrote:

quoted

From an arbitrary node in the tree, find the enclosing node that
corresponds to a platform device, as registered by
of_platform_populate().

This can be used to find out what device needs to be probed so the
dependency described by a given node is made available.

Signed-off-by: Tomeu Vizoso <redacted>
---

Changes in v2:
- Move the logic for finding a platform device from its firmware node to
  of/platform.c as it's not needed for ACPI nodes.

 drivers/of/platform.c       | 60 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/of_platform.h |  1 +
 2 files changed, 61 insertions(+)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index ff27494cda8c..89c5cd513027 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c

@@ -501,6 +501,66 @@ void of_platform_depopulate(struct device *parent)
 }
 EXPORT_SYMBOL_GPL(of_platform_depopulate);

+static bool of_is_platform(struct device_node *np)
+{
+       int count;
+
+       count = of_property_count_strings(np, "compatible");
+
+       /* The node has to have a compatible string */
+       if (!count)
+               return false;
+
+       /* But it cannot be just a simple memory-mapped bus */
+       if (count == 1 && of_match_node(of_default_bus_match_table, np))
+               return false;
+
+       /* But AMBA devices aren't platform devices */
+       if (of_device_is_compatible(np, "arm,primecell"))
+               return false;
+
+       /* Node is immediately below root */
+       if (!np->parent || !np->parent->parent)
+               return true;
+
+       /* If it's a node in a simple memory-mapped bus */
+       if (of_match_node(of_default_bus_match_table, np->parent))
+               return true;

This seems really fragile.

I think this finding logic matches the logic for registering platform
devices in of_platform_populate and also what is documented in
Documentation/devicetree/usage-model.txt.

What about platform devices which are
children of MFDs but are not "simple-mfd"?

This code should deal fine with those (the boards I tested with do
have them). It probes the mfd master, and that in turn will call
mfd_add_devices causing the target device to be probed.

Does of_find_device_by_node not work for you?

Well, the dependencies aren't always platform devices, that's why I
need to go up the tree until I find a node that corresponds to a
platform device that I can query and probe.

If I had a way to get, say, a i2c device from its fwnode then I would
just need to make sure that a device's parent is probed before probing
it and everything would be cleaner in the OF case.

That is probably not the
most efficient search, but we could fix that. We could add struct
device ptr to struct device_node and check without searching for
example.

That would be great, but I thought there was an issue with a OF node
being able to be related to more than one struct device (but I haven't
found this myself yet).

Thanks,

Tomeu

Rob
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