[PATCH V7 03/12] drm/bridge: Add helper functions for drm_bridge

[Ajay kumar]

On Mon, Nov 3, 2014 at 1:31 PM, Thierry Reding <thierry.reding at gmail.com> wrote:
> On Fri, Oct 31, 2014 at 04:51:43PM +0100, Daniel Vetter wrote:
>> On Wed, Oct 29, 2014 at 10:14:37AM +0100, Thierry Reding wrote:
>> > On Wed, Oct 29, 2014 at 09:57:02AM +0100, Daniel Vetter wrote:
>> > > That makes the entire thing a bit non-trivial, which is why I think it
>> > > would be better as some generic helper. Which then gets embedded or
>> > > instantiated for specific cases, like dt&drm_panel or dt&drm_bridge.
>> > > Or maybe even acpi&drm_bridge, who knows ;-)
>> >
>> > I worry a little about type safety. How will this generic helper know
>> > what registry to look in for? Or conversely, if all these resources are
>> > added to a single registry how do you know that they're of the correct
>> > type? Failing to ensure this could cause situations where you're asking
>> > for a panel and get a bridge in return because you've wrongly wired it
>> > up in device tree for example.
>> >
>> > But perhaps if both the registry and the device parts are turned into
>> > helpers we could still have a single core implementation and then
>> > instantiate that for each type, something roughly like this:
>> >
>> >     struct registry {
>> >             struct list_head list;
>> >             struct mutex lock;
>> >     };
>> >
>> >     struct registry_record {
>> >             struct list_head list;
>> >             struct module *owner;
>> >             struct kref *ref;
>> >
>> >             struct device *dev;
>> >     };
>> >
>> >     int registry_add(struct registry *registry, struct registry_record *record)
>> >     {
>> >             ...
>> >             try_module_get(record->owner);
>> >             ...
>> >     }
>> >
>> >     struct registry_record *registry_find_by_of_node(struct registry *registry,
>> >                                                      struct device_node *np)
>> >     {
>> >             ...
>> >             kref_get(...);
>> >             ...
>> >     }
>> >
>> > That way it should be possible to embed these into other structures,
>> > like so:
>> >
>> >     struct drm_panel {
>> >             struct registry_record record;
>> >             ...
>> >     };
>> >
>> >     static struct registry drm_panels;
>> >
>> >     int drm_panel_add(struct drm_panel *panel)
>> >     {
>> >             return registry_add(&drm_panels, &panel->record);
>> >     }
>> >
>> >     struct drm_panel *of_drm_panel_find(struct device_node *np)
>> >     {
>> >             struct registry_record *record;
>> >
>> >             record = registry_find_by_of_node(&drm_panels, np);
>> >
>> >             return container_of(record, struct drm_panel, record);
>> >     }
>> >
>> > Is that what you had in mind?
>>
>> Yeah I've thought that we should instantiate using macros even, so that we
>> have per-type registries. So you'd smash the usual set of
>> DECLARE/DEFINE_AUX_DEV_REGISTRY into headers/source files, and they'd take
>> a (name, key, value) tripled. For the example here(of_drm_panel, struct
>> device_node *, struct drm_panel *) or similar. I might be hand-waving over
>> a few too many details though ;-)
>
> Okay, I'll take a stab at this and see if I can convert DRM panel to it.
It would be great if you can do this soon. I would anyhow need a reference
for converting bridge framework as per Daniel's requirement :)

Ajay