linux-kernel - [PATCH] of/platform: depopulate devices in the reverse order of creation

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Date:   Mon, 12 Dec 2016 11:39:05 -0700
From:   Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:     Rob Herring <robh@...nel.org>,
        Frank Rowand <frowand.list@...il.com>
Cc:     Pawel Moll <pawel.moll@....com>,
        Grant Likely <grant.likely@...retlab.ca>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] of/platform: depopulate devices in the reverse order of
 creation

If the DT has inter-dependencies, then the devices need to be removed
in the right order to avoid removal problems.

Assuming the DT is constructed so that EPROBE_DEFER doesn't happen
during creating then a good way to avoid removal problems is reversing
the order during depopulation.

Signed-off-by: Jason Gunthorpe <jgunthorpe@...idianresearch.com>
---
 drivers/of/platform.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

In my specific case I have a gpio driver, followed by a i2c bitbang
using that driver. So gpiolib prints an error if it the gpio driver is
removed before the gpio client..

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index cd72c0156db2ba..5720fe44f991e9 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -568,7 +568,8 @@ static int of_platform_device_destroy(struct device *dev, void *data)
 void of_platform_depopulate(struct device *parent)
 {
 	if (parent->of_node && of_node_check_flag(parent->of_node, OF_POPULATED_BUS)) {
-		device_for_each_child(parent, NULL, of_platform_device_destroy);
+		device_for_each_child_reverse(parent, NULL,
+					      of_platform_device_destroy);
 		of_node_clear_flag(parent->of_node, OF_POPULATED_BUS);
 	}
 }
-- 
2.7.4