[alsa-devel] [PATCH 1/1] ASoC: Fix compilation error with davinci-sffsdr module

[Hugo Villeneuve]

On Thu, 15 Jan 2009 11:18:07 +0000
Mark Brown <broonie at sirena.org.uk> wrote:

> ")
> Fcc: +sent-mail
> 
> On Wed, Jan 14, 2009 at 03:54:06PM -0500, Hugo Villeneuve wrote:
> > Mark Brown <broonie at sirena.org.uk> wrote:
> 
> > > Speaking as the person who I expect most frequently tries that I 
> > > wouldn't worry about it - it's easy enough to see what's happened
> > > and there will still be errors at link time even with the extern.
> 
> > No, there won?t be errors when compiling as a module. Only when
> > actually loading the module.
> 
> Check again - the kernel will detect those errors at build time.  The
> module itself will compile but once all the modules are built Kbuild
> verifies that all the symbols they use can be found.

Hi Mark,
I just checked again and at first I tought you were wrong :)

Just to be sure, I cloned a fresh copy of linux-davinci-git kernel.
This tree doesn´t have the SFFSDR FPGA module with the
sffsdr_fpga_set_codec_fs() function.

If I compile this tree as is for the SFFSDR board, I sure have the
error for the missing header file <asm/plat-sffsdr/sffsdr-fpga.h>,
containing the declaration for the function sffsdr_fpga_set_codec_fs.
But if I remove the #include for that header file and add the following
extern declaration:

  extern int sffsdr_fpga_set_codec_fs(int fs);

I can successfully compile the whole kernel and all the selected
modules without any errors.

But in fact you were right, because I just found out that someone has
added the following check to sffsdr_init() in davinci-sffsdr.c:

        if (!machine_is_sffsdr())
                return -EINVAL;

For a reason that I don´t yet understand, that function doesn´t seem to
be defined (always return 0) and so gcc has correctly optimised my
module by removing the sffsdr_hw_params function, and thus also
removing the call to my sffsdr_fpga_set_codec_fs function, and this is
why Kbuild never complained!

> > > That's good news - previously it would fail to build at all.  What
> > > sort of breakage are you seeing (and what was the version you used
> > > when you developed the driver)?
> 
> > I developped the driver with version
> > 2.6.27-rc6-davinci1-05187-g91c2c53.
> 
> > The breakage I see when I run the aplay utility is this:
> 
> >   aplay: pcm_write:1394: write error: Input/output error
> 
> > davinci-git version is the latest as of january 14
> > (2.6.28-davinci1-06546-gcfb152b)
> 
> Hrm, OK.  That's not terribly informative - does the error get
> reported after about 10 seconds by any chance?  I suspect that DMA
> just isn't happening.

Sorry about the non-verbosity :)
Yes it happens almost exactly after 10 seconds. I´m not an expert with
audio nor DMA, but can you indicate me where I should be looking for
signs of trouble (which source files for example)?

Thank-you, Hugo.

---------------
Hugo Villeneuve
www.hugovil.com
---------------