[alsa-devel] [PATCH v2 2/2] ASoC: wm8985: add device-tree support

[Petr Kulhavy]

On 23 May 2016 at 10:31, Charles Keepax
<ckeepax at opensource.wolfsonmicro.com> wrote:
> On Mon, May 23, 2016 at 09:23:05AM +0200, Petr Kulhavy wrote:
>> On 20 May 2016 at 18:21, Charles Keepax
>> <ckeepax at opensource.wolfsonmicro.com> wrote:
>> > On Tue, May 17, 2016 at 02:49:49PM +0200, Petr Kulhavy wrote:
>> >> +static enum wm8985_type wm8985_data = WM8985;
>> >> +static enum wm8985_type wm8758_data = WM8758;
>> >> +
>> >> +static const struct of_device_id wm8985_of_match[] = {
>> >> +     { .compatible = "wlf,wm8985", .data = &wm8985_data},
>> >> +     { .compatible = "wlf,wm8758", .data = &wm8758_data},
>> >
>> > You can probably just use (void *)WM8985 instead here.
>>
>> I know this pretty safe with integers but can you do this with enums?
>> Doesn't it lead to undefined behaviour?
>
> Hmm... its not uncommon that it is done in the kernel, but
> that is rarely an indicator of if something is actually
> technically valid or not. Casting from an integer to a pointer
> is technically implementation defined, but we clearly rely on
> gcc's implementation in the kernel. However, without actually
> reading the spec in more detail I am unclear on if an enum counts
> as an integer here, my suspicion is that it would since it
> generally always implicitly casts to an int.
>
> I guess the correct fix is that .data should probably be a
> kernel_ulong_t in of_device_id. But if no one else objects I am
> happy for you to leave your current code as is.

If I understand this Stack Overflow answer right:
http://stackoverflow.com/a/2331327
The enum should be casted to an integer of size <= size of a pointer
for the architecture.
So this should be more or less ok?
.data = (void*)(int)WM8985

Thanks
Petr