On Fri, 25 Apr 2008, Takashi Iwai wrote:

Hm, indeed it's more than a single value...

For multiple anonymous data, we can use a data with a key like below:

	struct device_hint {
		char *key;
		void *data;
		struct list_head list;
	};

and the controller driver assigns the data like

	controller_init()
	{
		...
		controller.hint.key = "ucb1000-irq";
		controller.hint.data = whatever;
		list_add(&controller.hint. &ac97->device_hint_list);
		...
	}

and the device driver retrieves the data like

	device_init()
	{
		struct device_hint *hint;
		hint = device_hint_get(&ac97->device_hint_list, "ucb1000-irq");
		if (hint) {
			whatever = hint->data;
			...
		}
	}

where device_hint_get() is defined like

	struct device_hint *device_hint_get(struct device_hint *head,
			const char *key)
	{
		struct device_hint *hint;
		list_for_each_entry(hint, head, list)
			if (!strcmp(hint, key))
				return hint;
		return NULL;
	}

Of course, we can cast via container_of() to a container type instead
of using a void pointer there.

This is obviously an overweight for a single use-case, but if we have
more and more complex ones, maybe worth to consider.

Sure. I applied the simple 'void *device_private_data' patch, because 
current usage request is really trivial. We can implement complex code to 
handle data for multiple "extra" devices on AC97 bus later.

						Jaroslav

-----
Jaroslav Kysela [off-list ref]
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.