linux-kernel - Re: [PATCH v2 2/9] pwm: lpss: Move exported symbols to PWM

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Date:   Mon, 26 Sep 2022 11:55:47 +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 v2 2/9] pwm: lpss: Move exported symbols to PWM_LPSS
 namespace

On Mon, Sep 26, 2022 at 12:43:47PM +0300, Andy Shevchenko wrote:
> On Sat, Sep 24, 2022 at 11:59:45AM +0200, Uwe Kleine-König wrote:
> > Hello,
> > 
> > On Thu, Sep 08, 2022 at 04:56:51PM +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/
> > > 
> > > Suggested-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> > > 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, 4 insertions(+)
> > > 
> > > 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);
> > 
> > Each user of the lpss.h header needs that, right? Then the
> > MODULE_IMPORT_NS statement can go into the header, too.
> 
> With the same answer as for v1: any user that might include the header for
> the sake of data types will get the NS inclusion even if they don't need
> that (yes, I don't think it's practical, but slightly better to make sure

I'm not sure I understand you correctly here. For some headers you
cannot assume that a file including the header also needs the namespace
macro, but for pwm-lpss.h that should be a safe assumption.

> that if one uses an API, one adds necessary NS inclusions; also note that
> in case of stale header inclusion this again might bring unnecessary NS,
> while the header should be removed -- with that being said, I think we
> might need some kind of extended includecheck to see if the APIs and data
> structures are actually used when a certain header is included).

+1 for a check about unused headers.

Best regards
Uwe

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

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