Hi Peter,
On Sun, Sep 9, 2012 at 3:08 AM, Peter Hüwe <peterhu...@gmx.de> wrote:
>> > I'm curious if there have ever been any attempts to emulate i2c devices
>> > under uml in order to facilitate driver development by using stub
>> > drivers.
>> I know none.
>
>> If there is a use case, why not. :-)
> Thanks for your encouraging words ;)
>
> I had a look around and found the nice CONFIG_I2C_STUB driver,
> which is described in detail at
> http://www.kernel.org/doc/Documentation/i2c/i2c-stub
>
> """This module is a very simple fake I2C/SMBus driver. It implements five
> types of SMBus commands: write quick, (r/w) byte, (r/w) byte data, (r/w)
> word data, and (r/w) I2C block data."""
> which more or less exactly fits my need.
>
> The only thing that was missing was general support for I2C which is dependent
> on CONFIG_HAS_IOMEM which unfortunately isn't available on UML,
> but I simply added a || UML to the Kconfig and was now able to build the I2C
> Support, the i2c-dev module (for userspace access) and the i2c-stub driver.
Yes, that's what you typically have to do to get such a thing working.
JFYI, on several occasions, I worked on Amiga Zorro bus probing under UML, using
fake Zorro devices and real but stubbed network and frame buffer drivers.
> If I know load the i2c_stub module I have a emulated i2c device ;)
>
> I adapted the stub driver to my needs and was now able to create my own
> emulated i2c device and start with driver and tools development for it ;)
>
>
> I added the patch, in case you're interested.
>
> Unfortunately some I2C drivers fail to build if CONFIG_HAS_IOMEM = n, but
> don't have that dependency in Kconfig - I simply added it to prevent them from
> inclusion.
That's because they rely on the HAS_IOMEM dependency for the whole subsystem.
In fact, I'm surprised you didn't have to add HAS_IOMEM dependencies
to more drivers.
> Do you think I should try to push this mainline via the i2c subsystem?
As long as there are no "real" i2c drivers for UML, but only
dummy/development ones,
that is up to the i2c maintainer (in CC).
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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