[alsa-devel] module dependency between i915 and snd-hda-intel

Wang, Xingchao xingchao.wang at intel.com
Fri May 17 12:14:19 CEST 2013

> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai at suse.de]
> Sent: Friday, May 17, 2013 6:03 PM
> To: Wang, Xingchao
> Cc: Lin, Mengdong; david.henningsson at canonical.com; Li, Jocelyn; Girdwood,
> Liam R; alsa-devel at alsa-project.org
> Subject: Re: module dependency between i915 and snd-hda-intel
> At Fri, 17 May 2013 09:55:13 +0000,
> Wang, Xingchao wrote:
> >
> > Hi Takashi,
> >
> > Seems kernel building will determine the module loading sequence, this would
> fix the dependency for i915 and snd-hda-intel.
> > If we call the i915 module API directly in snd-hda-intel side, kernel building will
> change the module.dep accordingly like:
> > "
> > kernel/sound/pci/hda/snd-hda-intel.ko: kernel/drivers/gpu/drm/i915/i915.ko
> kernel/drivers/gpu/dr     m/drm_kms_helper.ko
> kernel/drivers/gpu/drm/drm.ko kernel/drivers/i2c/algos/i2c-algo-bit.ko kerne
> l/drivers/acpi/video.ko kernel/sound/pci/hda/snd-hda-codec.ko
> kernel/sound/core/snd-hwdep.ko ker     nel/sound/core/snd-pcm.ko
> kernel/sound/core/snd-timer.ko kernel/sound/core/snd.ko kernel/sound/s
> oundcore.ko kernel/sound/core/snd-page-alloc.ko
> > "
> > So snd-hda-intel will wait for i915 loading. Even I added i915 into blacklist.conf,
> it will force load i915.ko.
> >
> > So I think the only bad case is no i915 module built-in, that would cause
> haswell hda initialize fail, and the patch would output error message.
> Is it the result with your patch?  If so, something must be wrong.

No. i'm testing the case to call the API directly.
The issue is with current patch to load i915.ko by request_module(), It would take ~50s
and symbol_get() would fail, but I can see i915 module already there by "lsmod".

So is there any difference between request_module() and auto-loading i915 module?

> We don't want to call i915 functions directly from snd-hda-intel.
> That's the exact reason symbol_get() is used.  Otherwise i915 module is
> always referred, thus always load when HD-audio is used, no matter which
> hardware is.

Okay, I see.

> Takashi

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