linux-kernel - Re: [PATCH] ASoC: dwc: disallow building designware

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Date:   Tue, 18 Apr 2017 18:13:30 +0200
From:   Lubomir Rintel <lkundrak@...sk>
To:     Mark Brown <broonie@...nel.org>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] ASoC: dwc: disallow building designware_pcm as a module

On Tue, 2017-04-18 at 16:18 +0100, Mark Brown wrote:
> On Tue, Apr 18, 2017 at 12:59:54PM +0200, Lubomir Rintel wrote:
> > It makes not sense: the whether the PIO PCM extension is used is
> > hardcoded to the designware_i2s driver and designware_pcm doesn't
> > have any module metadata, causing a kernel taint:
> > 
> >   [   44.287000] designware_pcm: module license 'unspecified' taints kernel.
> > 
> > Signed-off-by: Lubomir Rintel <lkundrak@...sk>
> 
> This is not a a good approach, there is no technical reason to force the
> driver to be built in.  If you need a license tag in the module then add
> that.

I don't think designware_pcm is a separate driver. It looks tightly
coupled with designware_i2s: you can either disable designware_pcm
altogether at build time or always load it together with
designware_i2s.

See sound/soc/dwc/local.h:

  #if IS_ENABLED(CONFIG_SND_DESIGNWARE_PCM)
  void dw_pcm_push_tx(struct dw_i2s_dev *dev);
  int dw_pcm_register(struct platform_device *pdev);
  #else
  void dw_pcm_push_tx(struct dw_i2s_dev *dev) { }
  int dw_pcm_register(struct platform_device *pdev)
  {
          return -EINVAL;
  }
  #endif

Lubo