linux-kernel - Re: [PATCH] i2c: create builtin_i2c_driver to avoid registration boilerplate

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Date:	Tue, 12 Jan 2016 10:45:41 -0500
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	Wolfram Sang <wsa@...-dreams.de>
CC:	<linux-kernel@...r.kernel.org>, Lee Jones <lee.jones@...aro.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>,
	<linux-gpio@...r.kernel.org>, <linux-i2c@...r.kernel.org>
Subject: Re: [PATCH] i2c: create builtin_i2c_driver to avoid registration
 boilerplate

On 2015-12-13 03:33 PM, Paul Gortmaker wrote:
> In commit f309d4443130bf814e991f836e919dca22df37ae ("platform_device:
> better support builtin boilerplate avoidance") we introduced the
> builtin_driver macro.
> 
> Here we use that support and extend it to I2C driver registration,
> so where a driver is clearly non-modular and builtin-only, we can
> register it in a similar fashion.  And existing code that is clearly
> non-modular can be updated with the simple mapping of
> 
>      module_i2c_driver(...)  ---> builtin_i2c_driver(...)
> 
> We've essentially cloned the former to make the latter, and taken
> out the remove/module_exit parts since those never get used in a
> non-modular build of the code.
> 
> A similar thing was done in commit b4eb6cdbbd13698704863f680c643c569909e1c2
> ("PCI: Add builtin_pci_driver() to avoid registration boilerplate").
> 
> Cc: Wolfram Sang <wsa@...-dreams.de>
> Cc: Lee Jones <lee.jones@...aro.org>
> Cc: Linus Walleij <linus.walleij@...aro.org>
> Cc: Alexandre Courbot <gnurou@...il.com>
> Cc: linux-gpio@...r.kernel.org
> Cc: linux-i2c@...r.kernel.org
> Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
> ---
> 
> [I've about 10 drivers/mfd and one drivers/gpio users of this in
>  my personal testing queue, but obviously I can't submit those
>  until builtin_i2c_driver makes it to mainline.  Since there are
>  no drivers/i2c users yet this change is sent to i2c on its own.]

Hi Wolfram,

Was wondering if this is still in consideration for 4.5, so as per
the above info, I can make use of it in MFD in 4.6 without worrying
about cross maintainer dependencies.

Thanks,
Paul.
--
> 
>  include/linux/i2c.h | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index 768063baafbf..d3ca750bfcdf 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -622,7 +622,7 @@ static inline int i2c_adapter_id(struct i2c_adapter *adap)
>  }
>  
>  /**
> - * module_i2c_driver() - Helper macro for registering a I2C driver
> + * module_i2c_driver() - Helper macro for registering a modular I2C driver
>   * @__i2c_driver: i2c_driver struct
>   *
>   * Helper macro for I2C drivers which do not do anything special in module
> @@ -633,6 +633,17 @@ static inline int i2c_adapter_id(struct i2c_adapter *adap)
>  	module_driver(__i2c_driver, i2c_add_driver, \
>  			i2c_del_driver)
>  
> +/**
> + * builtin_i2c_driver() - Helper macro for registering a builtin I2C driver
> + * @__i2c_driver: i2c_driver struct
> + *
> + * Helper macro for I2C drivers which do not do anything special in their
> + * init. This eliminates a lot of boilerplate. Each driver may only
> + * use this macro once, and calling it replaces device_initcall().
> + */
> +#define builtin_i2c_driver(__i2c_driver) \
> +	builtin_driver(__i2c_driver, i2c_add_driver)
> +
>  #endif /* I2C */
>  
>  #if IS_ENABLED(CONFIG_OF)
>