linux-kernel - [PATCH 2/2] device core: Add flag to autoremove device link on supplier unbind

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Date:   Wed, 27 Jun 2018 18:20:56 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     rjw@...ysocki.net, linux-kernel@...r.kernel.org
Cc:     Vivek Gautam <vivek.gautam@...eaurora.org>,
        Jonathan Corbet <corbet@....net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Robin Murphy <robin.murphy@....com>, linux-doc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: [PATCH 2/2] device core: Add flag to autoremove device link on supplier unbind

Add a flag to autoremove the device links on supplier driver
unbind. This obviates the need to explicitly delete the link
in the remove path.
We remove these links only when the supplier's link to its
consumers has gone to DL_STATE_SUPPLIER_UNBIND state.

Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
Suggested-by: Lukas Wunner <lukas@...ner.de>
Cc: Jonathan Corbet <corbet@....net>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Robin Murphy <robin.murphy@....com>
Cc: linux-doc@...r.kernel.org
Cc: linux-arm-kernel@...ts.infradead.org
Cc: linux-pm@...r.kernel.org
Cc: linux-arm-msm@...r.kernel.org
---
 Documentation/driver-api/device_link.rst |  4 ++++
 drivers/base/core.c                      | 10 ++++++++++
 include/linux/device.h                   |  2 ++
 3 files changed, 16 insertions(+)

diff --git a/Documentation/driver-api/device_link.rst b/Documentation/driver-api/device_link.rst
index a005b904a264..d6763272e747 100644
--- a/Documentation/driver-api/device_link.rst
+++ b/Documentation/driver-api/device_link.rst
@@ -86,6 +86,10 @@ automatically purged when the consumer fails to probe or later unbinds.
 This obviates the need to explicitly delete the link in the ``->remove``
 callback or in the error path of the ``->probe`` callback.
 
+Similarly, when the device link is added from supplier's ``->probe`` callback,
+``DL_FLAG_AUTOREMOVE_SUPPLIER`` causes the device link to be automatically
+purged when the supplier fails to probe or later unbinds.
+
 Limitations
 ===========
 
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 14c1e3151e08..e721218bf352 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -518,6 +518,16 @@ void device_links_driver_cleanup(struct device *dev)
 
 		WARN_ON(link->flags & DL_FLAG_AUTOREMOVE_CONSUMER);
 		WARN_ON(link->status != DL_STATE_SUPPLIER_UNBIND);
+
+		/*
+		 * autoremove the links between this @dev and its consumer
+		 * devices that are not active, i.e. where the link state
+		 * has moved to DL_STATE_SUPPLIER_UNBIND.
+		 */
+		if (link->status == DL_STATE_SUPPLIER_UNBIND &&
+		    link->flags & DL_FLAG_AUTOREMOVE_SUPPLIER)
+			kref_put(&link->kref, __device_link_del);
+
 		WRITE_ONCE(link->status, DL_STATE_DORMANT);
 	}
 
diff --git a/include/linux/device.h b/include/linux/device.h
index 3929805cdd59..e80920452b49 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -787,11 +787,13 @@ enum device_link_state {
  * AUTOREMOVE_CONSUMER: Remove the link automatically on consumer driver unbind.
  * PM_RUNTIME: If set, the runtime PM framework will use this link.
  * RPM_ACTIVE: Run pm_runtime_get_sync() on the supplier during link creation.
+ * AUTOREMOVE_SUPPLIER: Remove the link automatically on supplier driver unbind.
  */
 #define DL_FLAG_STATELESS		BIT(0)
 #define DL_FLAG_AUTOREMOVE_CONSUMER	BIT(1)
 #define DL_FLAG_PM_RUNTIME		BIT(2)
 #define DL_FLAG_RPM_ACTIVE		BIT(3)
+#define DL_FLAG_AUTOREMOVE_SUPPLIER	BIT(4)
 
 /**
  * struct device_link - Device link representation.
-- 
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