Re: [RFC] power trees

[Pavel Machek <pavel@ucw.cz>]

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Hi!

> My implementation has two primary goals:
> 
> 1.) To help device drivers track and control their device's power state
> 
> 2.) To bubble power state dependency changes from a leaf node to the
> last affected parent node in the chain.
> 
> The basic unit of the tree is referred to as a "pm_node".  Each
> "pm_node" has a list of states it supports, a current state, and a
> driver to handle state transitions.  Any "pm_node" can have children and
> therefore act as a power container.
> 
> struct pm_state {
> 	char			*name;
> 	unsigned long		index;
> 	unsigned long		link_req;
> 	void			*link_data;
> };
> 
> "index" is a driver specific value that indicates the state.  "link_req"
> is a set of flags that indicate requirements from the parent "pm_node".
> "link_data" provides additional requirement information.
> 
> struct pm_node {
> 	struct semaphore	sem;
> 	struct list_head	children;
> 	struct list_head	child_list;
> 	struct pm_node		*parent;
> 	struct pm_node		*tmp_path;
> 	struct device		*dev;
> 
> 	struct pm_node_driver	*drv;
> 	unsigned int		current_state;
> 	unsigned int		target_state;

Would not it be cleaner to have struct pm_state *current_state, target state?

> "states" is a list of power states sorted from most functional to least
> functional.  "current_state" and "target_state" are index values for
> that list.
> 
> struct pm_node_driver {
> 	int (*set_state) 	(struct pm_node *node);
> 	int (*raise_event)	(struct pm_node *domain,
> 				 struct pm_node *child,
> 				 unsigned long *new_state);

struct pm_state here, too?

> 	void (*lower_event)	(struct pm_node *domain);
> };
> 
> "raise_event" notifies the power domain when a child has increased its

"Increase" == went more power hungry?

> I apologize for the unpolished/untested state of the code as it's
> primarily intended to illustrate a concept.  I'll need to look over the
> problem more carefully if we decide this is the right direction.  Power

Seems ok to me.

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