linux-kernel - [PATCH 2/2] i2c: core: support no-detect property

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Message-ID: <20220405121627.1560949-3-vincent.whitchurch@axis.com>
Date:   Tue, 5 Apr 2022 14:16:27 +0200
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     <wsa@...nel.org>
CC:     <kernel@...s.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        <linux-i2c@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <krzk+dt@...nel.org>, <robh+dt@...nel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/2] i2c: core: support no-detect property

If the devicetree specifies the no-detect property, we can avoid calling
drivers' detect callback and wasting time probing for devices which do
not exist.

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
---
 drivers/i2c/i2c-core-base.c | 8 +++++++-
 include/linux/i2c.h         | 1 +
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index d43db2c3876e..d43025b84546 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -1341,7 +1341,8 @@ static int i2c_do_add_adapter(struct i2c_driver *driver,
 			      struct i2c_adapter *adap)
 {
 	/* Detect supported devices on that bus, and instantiate them */
-	i2c_detect(adap, driver);
+	if (adap->detect)
+		i2c_detect(adap, driver);
 
 	return 0;
 }
@@ -1432,6 +1433,7 @@ EXPORT_SYMBOL_GPL(i2c_handle_smbus_host_notify);
 
 static int i2c_register_adapter(struct i2c_adapter *adap)
 {
+	struct device_node *np = adap->dev.of_node;
 	int res = -EINVAL;
 
 	/* Can't register until after driver model init */
@@ -1502,6 +1504,10 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
 			 "Failed to create compatibility class link\n");
 #endif
 
+	adap->detect = true;
+	if (np && of_property_read_bool(np, "no-detect"))
+		adap->detect = false;
+
 	/* create pre-declared device nodes */
 	of_i2c_register_devices(adap);
 	i2c_acpi_install_space_handler(adap);
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index fbda5ada2afc..8fad5fe85685 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -728,6 +728,7 @@ struct i2c_adapter {
 	struct rt_mutex bus_lock;
 	struct rt_mutex mux_lock;
 
+	bool detect;
 	int timeout;			/* in jiffies */
 	int retries;
 	struct device dev;		/* the adapter device */
-- 
2.34.1