[alsa-devel] [PATCH] ASoC: wm8962: Convert to devm_input_allocate_device()

[Dmitry Torokhov]

On Mon, Apr 29, 2013 at 11:07:28AM -0700, Dmitry Torokhov wrote:
> On Mon, Apr 29, 2013 at 08:47:37PM +0300, Leon Romanovsky wrote:
> > On Mon, Apr 29, 2013 at 1:19 PM, Mark Brown <broonie at kernel.org> wrote:
> > > On Sun, Apr 28, 2013 at 09:32:18PM +0300, Leon Romanovsky wrote:
> > >
> > >> I think the reason of our misunderstanding is due to the name of
> > >> input_free_device call. From the code, it is device destroy function,
> > >> and the freeing itself done as an error handling of
> > >> input_register_device
> > >> (http://lxr.free-electrons.com/source/drivers/input/input.c#L2114).
> > >
> > >> How do you think we need to proceed? Do I need to send patches with
> > >> explicit call to input_free_device function?
> > >
> > > I really think the input API needs to be looked at here, this is all way
> > > too error prone.  Calling input_free_device() on something allocated
> > > using devm_ looks like an error itself...
> > In general, I agree with you, but I think we both agree that the
> > current patch is not working as expected.
> > The problem is that you allocated device with devm_ and later at the
> > code you tried to register it, but failed. In this case no one will
> > call to devres_destroy, because it is done at unregister stage only.
> > 
> > I see two possible solutions:
> > 1. short one - fix your patches
> > 2. long one - add input_free_device code into input_register_device
> > call (http://lxr.free-electrons.com/source/drivers/input/input.c#L2114).
> > 
> 
> The rules are pretty straightforward:
> 
> 1. If you are using devm_input_allocate_device() you do not need to call
> input_free_device() nor input_unregister_device()  - the core will
> create a devres structure for freeing the device and if
> input_register_device() succeeds it will also add a 2nd devres for
> unregistering. This way the "normal" unwind is a 2-step process with
> device is "half alive" and being able to survive input_event() calls
> from IRQ handlers if they are still alive.
> 
> IOW  it should all "just work".
> 
> 2. If you are using input_allocate_device() then you need to call
> input_free_device() until you called input_register_device(), afterward
> input_unregister_device() should be called.
> 

BTW, looking at Marks patch it looks good to me.

-- 
Dmitry