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Wysocki" , Greg Kroah-Hartman Subject: [PATCH v9 1/5] driver core: Find an existing link between two devices Date: Tue, 13 Mar 2018 14:25:30 +0530 Message-Id: <20180313085534.11650-2-vivek.gautam@codeaurora.org> X-Mailer: git-send-email 2.16.1.72.g5be1f00a9a70 In-Reply-To: <20180313085534.11650-1-vivek.gautam@codeaurora.org> References: <20180313085534.11650-1-vivek.gautam@codeaurora.org> X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1594812129788829883?= X-GMAIL-MSGID: =?utf-8?q?1594812129788829883?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 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 Cc: Rafael J. Wysocki Cc: Greg Kroah-Hartman --- * 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