Re: [PATCH] pwm-backlight: add regulator and GPIO support

On Wed, Jul 04, 2012 at 09:26:58PM +0900, Alex Courbot wrote:

On 07/04/2012 07:48 PM, Sascha Hauer wrote:>> +

quoted

This looses several resources allocated earlier, like the enable gpio
and the pwm. This is really bad here since I have no regulator specified
and devm_regulator_get returns with -EPROBE_DEFER. Next time the core
tries to probe the driver the driver bails out because the gpio and the
pwm is already requested.

That's very bad indeed. I assumed that the kernel would free
devm-allocated resources after probe returned -EPROBE_DEFER, so that
probe could reallocate them the next time it is called. Apparently
that was wrong. Do you know what would the right approach be in this
case? Does the kernel preserve the device structure and its
associated data between the two calls to probe? If so, I could just
check whether the private data has already been constructed to know
which state we are in and continue from there.

I'd really expect the devm_ functions to behave as you expect - if they
don't currently we should probably fix them so that they do otherwise
we're going to be in for a lot of surprises and probe deferral becomes a
lot more cumbersome to use.