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Subject[PATCH v9 1/5] driver core: Find an existing link between two devices
Date
The lists managing the device-links can be traversed to
find the link between two devices. The device_link_add() APIs
does traverse these lists to check if there's already a link
setup between the two devices.
So, add a new APIs, device_link_find(), to find an existing
device link between two devices - suppliers and consumers.

Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

* New patch added to this series.

drivers/base/core.c | 30 +++++++++++++++++++++++++++---
include/linux/device.h | 2 ++
2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 5847364f25d9..e8c9774e4ba2 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -144,6 +144,30 @@ static int device_reorder_to_tail(struct device *dev, void *not_used)
return 0;
}

+/**
+ * device_link_find - find any existing link between two devices.
+ * @consumer: Consumer end of the link.
+ * @supplier: Supplier end of the link.
+ *
+ * Returns pointer to the existing link between a supplier and
+ * and consumer devices, or NULL if no link exists.
+ */
+struct device_link *device_link_find(struct device *consumer,
+ struct device *supplier)
+{
+ struct device_link *link = NULL;
+
+ if (!consumer || !supplier)
+ return NULL;
+
+ list_for_each_entry(link, &supplier->links.consumers, s_node)
+ if (link->consumer == consumer)
+ break;
+
+ return link;
+}
+EXPORT_SYMBOL_GPL(device_link_find);
+
/**
* device_link_add - Create a link between two devices.
* @consumer: Consumer end of the link.
@@ -195,9 +219,9 @@ struct device_link *device_link_add(struct device *consumer,
goto out;
}

- list_for_each_entry(link, &supplier->links.consumers, s_node)
- if (link->consumer == consumer)
- goto out;
+ link = device_link_find(consumer, supplier);
+ if (link)
+ goto out;

link = kzalloc(sizeof(*link), GFP_KERNEL);
if (!link)
diff --git a/include/linux/device.h b/include/linux/device.h
index b093405ed525..13bc1884c3eb 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1278,6 +1278,8 @@ extern const char *dev_driver_string(const struct device *dev);
struct device_link *device_link_add(struct device *consumer,
struct device *supplier, u32 flags);
void device_link_del(struct device_link *link);
+struct device_link *device_link_find(struct device *consumer,
+ struct device *supplier);

#ifdef CONFIG_PRINTK

--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation
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