linux-kernel - Re: [RFC] i2c: add deprecation warning for class based instantiation

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Date:	Wed, 19 Jun 2013 21:22:00 +0300
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Wolfram Sang <wsa@...-dreams.de>
CC:	<linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-omap@...r.kernel.org>
Subject: Re: [RFC] i2c: add deprecation warning for class based instantiation

On 06/07/2013 12:09 PM, Wolfram Sang wrote:
> Class based instantiation can cause huge delays when booting. This
> mechanism was used when it was not possible to describe slaves on I2C
> busses. We now have other mechanisms, so most embedded I2C will not need
> classes and it was explicitly not recommended to use them. Add a
> deprecation warning for drivers who want to disable class based 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@...-dreams.de>
> ---
>   drivers/i2c/busses/i2c-omap.c |    2 +-
>   drivers/i2c/i2c-core.c        |    6 ++++++
>   include/linux/i2c.h           |    1 +
>   3 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index e02f9e3..f06109f 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -1231,7 +1231,7 @@ omap_i2c_probe(struct platform_device *pdev)
>   	adap = &dev->adapter;
>   	i2c_set_adapdata(adap, dev);
>   	adap->owner = THIS_MODULE;
> -	adap->class = I2C_CLASS_HWMON;
> +	adap->class = I2C_CLASS_HWMON | I2C_CLASS_DEPRECATED;
>   	strlcpy(adap->name, "OMAP I2C adapter", sizeof(adap->name));
>   	adap->algo = &omap_i2c_algo;
>   	adap->dev.parent = &pdev->dev;
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index 48e31ed..47ea1f0 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -999,6 +999,12 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
>   		return -EINVAL;
>   	}
>   
> +	if (adap->class & I2C_CLASS_DEPRECATED)
> +		dev_warn(&adap->dev, "This adapter will soon drop class based "
> +			"instantiation of slaves\nPlease make sure all its I2C "
> +			"devices are instantiated by other means.\nCheck "
> +			"'Documentation/i2c/instantiating-devices' for details\n");
> +
Seems, this need to be moved down - after     res = 
device_register(&adap->dev);
- or - right before:     bus_for_each_drv(&i2c_bus_type, NULL, adap, 
__process_new_adapter);


>   	rt_mutex_init(&adap->bus_lock);
>   	mutex_init(&adap->userspace_clients_lock);
>   	INIT_LIST_HEAD(&adap->userspace_clients);
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index e988fa9..ffab838 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -473,6 +473,7 @@ 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



- grygorii
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