linux-kernel - Re: [PATCH] power_supply: change the way how wm97xx-bat driver is registered

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Date:	Mon, 3 Nov 2008 18:11:51 +0300
From:	Anton Vorontsov <avorontsov@...mvista.com>
To:	Dmitry Baryshkov <dbaryshkov@...il.com>
Cc:	linux-kernel@...r.kernel.org, cbou@...l.ru,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Vasut <marek.vasut@...il.com>,
	Jonathan Cameron <Jonathan.Cameron@...il.com>
Subject: Re: [PATCH] power_supply: change the way how wm97xx-bat driver is
	registered

On Wed, Oct 29, 2008 at 12:04:10PM +0300, Dmitry Baryshkov wrote:
> Do register the driver from wm97xx_bat_set_pdata instead of module init.
> This has several positive outcome points:
> 1) This driver for wm97xx-battery is now registered on demand, thus allowing
>   other driver (e.g. tosa-battery) to claim the battery.
> 2) After dropping __init from wm97xx_bat_set_pdata(), the wm97xx_bat driver
>   can be correctly built as a module. Then one can request it and set the
>   battery data.
> 
> Signed-off-by: Dmitry Baryshkov <dbaryshkov@...il.com>
> Cc: Marek Vasut <marek.vasut@...il.com>
> ---
>  drivers/power/Kconfig          |    4 ++--
>  drivers/power/wm97xx_battery.c |   12 +++++-------
>  include/linux/wm97xx_batt.h    |    7 +++++--
>  3 files changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/power/Kconfig b/drivers/power/Kconfig
> index 8e0c2b4..053f20b 100644
> --- a/drivers/power/Kconfig
> +++ b/drivers/power/Kconfig
> @@ -57,8 +57,8 @@ config BATTERY_TOSA
>  	  SL-6000 (tosa) models.
>  
>  config BATTERY_WM97XX
> -	bool "WM97xx generic battery driver"
> -	depends on TOUCHSCREEN_WM97XX=y
> +	tristate "WM97xx generic battery driver"
> +	depends on TOUCHSCREEN_WM97XX
>  	help
>  	  Say Y to enable support for battery measured by WM97xx aux port.
>  
> diff --git a/drivers/power/wm97xx_battery.c b/drivers/power/wm97xx_battery.c
> index 8bde921..94727dc 100644
> --- a/drivers/power/wm97xx_battery.c
> +++ b/drivers/power/wm97xx_battery.c
> @@ -248,23 +248,21 @@ static struct platform_driver wm97xx_bat_driver = {
>  	.resume		= wm97xx_bat_resume,
>  };
>  
> -static int __init wm97xx_bat_init(void)
> -{
> -	return platform_driver_register(&wm97xx_bat_driver);
> -}
> -
>  static void __exit wm97xx_bat_exit(void)
>  {
>  	platform_driver_unregister(&wm97xx_bat_driver);
>  }
>  
> -void __init wm97xx_bat_set_pdata(struct wm97xx_batt_info *data)
> +int wm97xx_bat_set_pdata(struct wm97xx_batt_info *data)
>  {
> +	if (pdata)
> +		return -EEXIST;
> +
>  	pdata = data;
> +	return platform_driver_register(&wm97xx_bat_driver);
>  }
>  EXPORT_SYMBOL_GPL(wm97xx_bat_set_pdata);
>  
> -module_init(wm97xx_bat_init);
>  module_exit(wm97xx_bat_exit);
>  
>  MODULE_LICENSE("GPL");
> diff --git a/include/linux/wm97xx_batt.h b/include/linux/wm97xx_batt.h
> index 9681d1a..3e42526 100644
> --- a/include/linux/wm97xx_batt.h
> +++ b/include/linux/wm97xx_batt.h
> @@ -18,9 +18,12 @@ struct wm97xx_batt_info {
>  };
>  
>  #ifdef CONFIG_BATTERY_WM97XX
> -void __init wm97xx_bat_set_pdata(struct wm97xx_batt_info *data);
> +int wm97xx_bat_set_pdata(struct wm97xx_batt_info *data);
>  #else
> -static inline void wm97xx_bat_set_pdata(struct wm97xx_batt_info *data) {}
> +static inline int wm97xx_bat_set_pdata(struct wm97xx_batt_info *data)
> +{
> +	return -ENODEV;
> +}
>  #endif

How that supposed to work when BATTERY_WM97XX is a module?
#ifdef CONFIG_BATTERY_WM97XX will evaluate to false, and you'll have
dummy wm97xx_bat_set_pdata() that returns -ENODEV...

The whole wm97xx stuff is broken wrt device-driver model... Yeah,
I know why -- we don't have the ADC API/Subsystem. It would be great
if somebody could find time to forward-port the subsystem from the
handhelds.org tree...

I don't know what happened to the industrialio subsystem though
(http://lkml.org/lkml/2008/7/23/163), but it looked needlessly
complicated, and probably Jonathan gave up on it... :-/

-- 
Anton Vorontsov
email: cbouatmailru@...il.com
irc://irc.freenode.net/bd2
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