linux-kernel - Re: [PATCH v1 2/9] pwm: lpss: Move exported symbols to PWM

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Message-ID: <20220907091144.picr3byckxco7w6m@pengutronix.de>
Date:   Wed, 7 Sep 2022 11:11:44 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org,
        Thierry Reding <thierry.reding@...il.com>
Subject: Re: [PATCH v1 2/9] pwm: lpss: Move exported symbols to PWM_LPSS
 namespace

Hello Andy,

On Tue, Sep 06, 2022 at 10:57:28PM +0300, Andy Shevchenko wrote:
> Avoid unnecessary pollution of the global symbol namespace by
> moving library functions in to a specific namespace and import
> that into the drivers that make use of the functions.
> 
> For more info: https://lwn.net/Articles/760045/
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  drivers/pwm/pwm-lpss-pci.c      | 1 +
>  drivers/pwm/pwm-lpss-platform.c | 1 +
>  drivers/pwm/pwm-lpss.c          | 2 +-
>  3 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pwm/pwm-lpss-pci.c b/drivers/pwm/pwm-lpss-pci.c
> index 75b778e839b3..9f2c666b95ec 100644
> --- a/drivers/pwm/pwm-lpss-pci.c
> +++ b/drivers/pwm/pwm-lpss-pci.c
> @@ -92,3 +92,4 @@ module_pci_driver(pwm_lpss_driver_pci);
>  
>  MODULE_DESCRIPTION("PWM PCI driver for Intel LPSS");
>  MODULE_LICENSE("GPL v2");
> +MODULE_IMPORT_NS(PWM_LPSS);
> diff --git a/drivers/pwm/pwm-lpss-platform.c b/drivers/pwm/pwm-lpss-platform.c
> index fcd80cca2f6d..96fde1b2b967 100644
> --- a/drivers/pwm/pwm-lpss-platform.c
> +++ b/drivers/pwm/pwm-lpss-platform.c
> @@ -87,4 +87,5 @@ module_platform_driver(pwm_lpss_driver_platform);
>  
>  MODULE_DESCRIPTION("PWM platform driver for Intel LPSS");
>  MODULE_LICENSE("GPL v2");
> +MODULE_IMPORT_NS(PWM_LPSS);
>  MODULE_ALIAS("platform:pwm-lpss");

While it's not wrong to add the IMPORT_NS statement to each file, I'd
had added it to pwm-lpss.h. IMHO that makes sense as every includer of
that header needs that IMPORT_NS to actually use the symbols declared
there.

> diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
> index 36d4e83e6b79..a82a57eb2482 100644
> --- a/drivers/pwm/pwm-lpss.c
> +++ b/drivers/pwm/pwm-lpss.c
> @@ -250,7 +250,7 @@ struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r,
>  
>  	return lpwm;
>  }
> -EXPORT_SYMBOL_GPL(pwm_lpss_probe);
> +EXPORT_SYMBOL_NS_GPL(pwm_lpss_probe, PWM_LPSS);

There is something possible with more magic:

	#define DEFAULT_SYMBOL_NAMESPACE PWM_LPSS

which you only need once in pwm-lpss.c and then all exports use that
namespace. (And if you pick up my suggestion for patch 1 you also
benefit from that.)

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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