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SubjectRe: [PATCH v2 1/3] software node: implement reference properties
On Sat, Sep 07, 2019 at 07:08:19PM +0300, Andy Shevchenko wrote:
> On Fri, Sep 06, 2019 at 03:26:09PM -0700, Dmitry Torokhov wrote:
> > It is possible to store references to software nodes in the same fashion as
> > other static properties, so that users do not need to define separate
> > structures:
> >
> > static const struct software_node gpio_bank_b_node = {
> > .name = "B",
> > };
> >
> > static const struct property_entry simone_key_enter_props[] = {
> > PROPERTY_ENTRY_U32("linux,code", KEY_ENTER),
> > PROPERTY_ENTRY_STRING("label", "enter"),
> > PROPERTY_ENTRY_REF("gpios", &gpio_bank_b_node, 123, GPIO_ACTIVE_LOW),
> > { }
> > };
> >
>
> Thanks for an update, my comments below.
>
> > + } else if (src->type == DEV_PROP_REF) {
> > + /* All reference properties must be arrays */
> > + return -EINVAL;
>
> Hmm... What about to duplicate pointer under value union and use is_array to
> distinguish which one to use? Because...

Then we have to special-case copying this entry, similar to the pains we
are going with the strings.

>
>
> > @@ -240,6 +254,7 @@ struct property_entry {
> > const u32 *u32_data;
> > const u64 *u64_data;
> > const char * const *str;
> > + const struct software_node_ref_args *ref;
> > } pointer;
>
> > +#define PROPERTY_ENTRY_REF(_name_, _ref_, ...) \
> > +(struct property_entry) { \
> > + .name = _name_, \
>
> > + .length = sizeof(struct software_node_ref_args), \
>
> Is it correct?

Yes, we length is element size * number of elements.

>
> > + .type = DEV_PROP_REF, \
>
> > + .is_array = true, \
>
> I really don't like this "cheating".

This is not cheating. Any single value can be represented as an array of
one element. Actually, the only reason we have this "is_array" business
is because for scalar values and short strings it is much cheaper to
store single value in-line instead of out of line + pointer, especially
on 64 bit arches.

If you want we can change is_array into is_inline.

Thanks.

--
Dmitry

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