[alsa-devel] [PATCH v3] ASoC CS4270 codec device driver
timur at freescale.com
Tue Jul 31 20:53:16 CEST 2007
Trent Piepho wrote:
> If config FOO is compiled in (i.e. it's "y"), CONFIG_FOO will be defined.
> If it's a module, CONFIG_FOO_MODULE will be defined. It's one or the
> other, not both.
Learn something new every day. I should have known that already, though.
> If you want your code to comple differently if it has i2c available, you should
> do this:
> #if defined(CONFIG_I2C) || (defined(CONFIG_I2C_MODULE) && defined(MODULE))
> /* code that needs i2c goes here, i2c_transfer(), etc. */
> Note that just checking defined(CONFIG_I2C_MODULE) isn't correct. If your
> code is compiled in and i2c is a module, you can't call i2c functions or
> the kernel won't link.
Which is a problem because ASoC currently requires all modules to be linked together. The
machine driver has hard-coded references to structures in the other drivers.
I think Liam was trying to fix that with the PowerPC branch, but it doesn't look like he's
> Of course, if you need i2c to work in any reasonble way, you should just
> have your driver depend on i2c in Kconfig.
Well, that's the odd thing about the CS4270 - it's not required. The CS4270 can work with
or without I2C. I tried writing the driver to be intelligent about that - if I2C is
enabled, but the device can't be found on the I2C bus, it falls back to "stand-alone" mode.
It looks like I'm not really going to be able to support stand-alone mode yet, anyway. So
I'll just try to make it compile when I2C is disabled.
Linux Kernel Developer @ Freescale
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