[alsa-devel] [PATCH 7/9] ASoC: Intel: move PCI probe to a seprate file

[Takashi Iwai]

At Thu, 30 Oct 2014 21:07:19 +0530,
Vinod Koul wrote:
> 
> On Thu, Oct 30, 2014 at 04:27:09PM +0100, Takashi Iwai wrote:
> > > > The standard way is something like
> > > > 
> > > > snd-intel-sst-y := sst.o sst_ipc.o sst_stream.o sst_drv_interface.o sst_loader.o sst_pvt.o
> > > > snd-intel-sst-$(CONFIG_SND_SST_IPC_PCI) += sst_pci.o
> > > > 
> > > > But, when looking at the later patch, you try to build ACPI stuff into
> > > > snd-intel-sst, too, and both are implemented as exclusive.  This
> > > > doesn't work well in general.
> > > The hardware, firmware so the driver is pretty same. So either it gets probed
> > > as PCI device is SFI platforms and as APCI device on ACPI ones.
> > > Since the probe method is the only one differing, the machine will select
> > > either PCI or ACPI. That one would get compiled in.
> > 
> > ... and this exclusion mechanism is missing in your patches.
> > Your current code doesn't allow to mix them.
> > 
> > > Am okay to change if we have better method which works for both
> > 
> > In general, it's better to provide individual modules for different
> > interfaces and a common module that is referred by them.  The
> > selective build makes the build tests more difficult and is rather
> > error-prone.
> Hmmm, that makes me wonder why cant we do (based on your input above)
> 
> snd-intel-sst-y := sst.o sst_ipc.o sst_stream.o sst_drv_interface.o sst_loader.o sst_pvt.o
> 
> then either this:
> snd-intel-sst-$(CONFIG_SND_SST_IPC_PCI) += sst_pci.o
> snd-intel-sst-$(CONFIG_SND_SST_IPC_ACPI) += sst_acpi.o

This may compile both sst_pci.c and sst_acpi.c into snd-intel-sst
module, so it doesn't work unless both Kconfigs are really exclusive.

> Or:
> snd-intel-sst-pci-y += snd-intel-sst.o sst_pci.o
> snd-intel-sst-acpi-y += snd-intel-sst.o sst_acpi.o

This is wrong in two ways.  First off, you can't link a module against
another module.

Second, this causes the problem when user build one driver as a module
and another as built-in.  Then you'll get the doubly symbols.

So, snd-intel-sst.o must be an individual module.


Takashi