Re: [PATCH 2/5] i2c: sh_mobile: add DMA support

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On Thursday 11 December 2014 22:47:32 Wolfram Sang wrote:
> > > Note that the I2C drives uses subsys_initcall() for historic reasons,
> > > while the DMA driver uses module_init(). This is hard to revert without
> > > introducing potential regressions on older boards. So, the I2C DMA
> > > support needs to handle deferred probe definately. I am with Laurent, I
> > > don't see any other way, but I'd be glad to be enlightened...
> > 
> > While I believe that requesting the channel at transfer time is the good
> > solution, I think we should still try to move to module initcalls where
> > possible. The risk of regressions is real so proper testing is needed. My
> > question is, have you tried it ?
> 
> I would need to test all boards using this driver to not fail booting.
> Usually I2C drivers are moved to subsys_initcall because they need
> access to something critical (PMIC, GPIOs...) early. I don't see a sane
> way to do that testing.

Still, I would like to get a better view on the problems we should expect, by 
testing this on the latest boards for instance.

> Other than that, even if we move to module_init, we reduce the chance of
> getting a deferred probe, but we do not eliminate it...

Sure, but reducing the chance of deferred probe is a good idea in my opinion 
:-)

-- 
Regards,

Laurent Pinchart

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