i2c: add deprecation warning for class based instantiation (0c176170) · Commits · 戴 / test

Class based instantiation can cause noticeable delays when booting. This mechanism is used when it is not possible to describe slaves on I2C busses. As we do have other mechanisms, most embedded I2C will not need classes and for embedded it is explicitly not recommended to use them. Add a deprecation warning for drivers which want to disable class based instantiation in the near future to gain boot-up time, so users relying on this technique can switch to something better. They really should. Signed-off-by:

Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/i2c-core.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -1941,6 +1941,13 @@ static int i2c_detect_address(struct i2c_client *temp_client,
		struct i2c_client *client;

		/* Detection succeeded, instantiate the device */
		if (adapter->class & I2C_CLASS_DEPRECATED)
		dev_warn(&adapter->dev,
		"This adapter will soon drop class based instantiation of devices. "
		"Please make sure client 0x%02x gets instantiated by other means. "
		"Check 'Documentation/i2c/instantiating-devices' for details.\n",
		info.addr);

		dev_dbg(&adapter->dev, "Creating %s at 0x%02x\n",
		info.type, info.addr);
		client = i2c_new_device(adapter, &info);

include/linux/i2c.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -487,6 +487,7 @@ void i2c_unlock_adapter(struct i2c_adapter *);
		#define I2C_CLASS_HWMON (1<<0) /* lm_sensors, ... */
		#define I2C_CLASS_DDC (1<<3) /* DDC bus on graphics adapters */
		#define I2C_CLASS_SPD (1<<7) /* Memory modules */
		#define I2C_CLASS_DEPRECATED (1<<8) /* Warn users that adapter will stop using classes */

		/* Internal numbers to terminate lists */
		#define I2C_CLIENT_END 0xfffeU

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