Re: [PATCH] extcon : callback function to read cable property

[Anton Vorontsov <cbouatmailru@gmail.com>]

On Tue, Nov 20, 2012 at 09:14:41AM +0000, Tc, Jenny wrote:
[...]
> > For example,
> > Firstly, the power_supply charging framework check state of charger cable
> > whether attached or detached cable. Second, when power_supply charging
> > framework receive the changed state of host system from 'Host system
> > notifier', change charging current of charger cable.
> 
> Not just SUSPEND, but we need to handle RESUME , UPDATE etc.  Also this doesn’t help us to
> define a standard interface for the charger cable state/properties. IMHO it's not right
> to provide different interfaces for different cables. This doesn't help us to standardize
> the charger cable interface.
> 
> This thread has been running for a quite long time. Unfortunately we couldn't make an
> agreement on the final solution. I would like to recap the overall requirement and
> would like to propose alternate solutions. The requirements is  to
> "Provide a generic interface for charger cable states and charger cable properties"
> 
> Even though extcon subsystem handles charger cable states, it's not enough to handle
> all kind of charger cable states. It can handle just 2 states CONNECT/DISCONNECT.
> But there are scenarios where we need to handle more than 2 states
> (eg. USB SUSPEND/RESUME/UPDATE etc). Also extcon doesn't have any mechanism to
> read cable properties in a generic way.  Extcon charger-cable consumer driver
> implementations (eg charger-manager), defines charger cable properties statically (current in mA)
> inside the consumer driver. This is not enough, since the charger cable properties may change dynamically
> 
> In existing form extcon cannot support different charger cable states and their 
> properties in a generic way. Also we couldn't find a final solution on how to modify the
> extcon to support these requirements. From the whole discussion what I conclude is
>  * extcon is not designed to support cable properties

The idea of using union seemed good to me, what happened to it?

I mean, MyungJoo Ham wrote:

| We may have:
|        enum extcon_cable_type {
|                EXTCON_CT_REGULATOR,
|                EXTCON_CT_PSY,
|                EXTCON_CT_CHARGER_CB,
|                ...
|        };
| and have the following included at struct extcon_cable:
|        union {
|                struct regulator *reg;
|                struct power_supply *psy;
|                struct charger_cable *charger_cb;
|                ...
|        } cable data;
|        enum extcon_cable_type cable_type;

This sounds good to me...

>  * extcon is not designed to support any cable state other than CONNECT/DISCONNECT

Dunno for this one. Can we get these additional states via "properties" as
described above?

Thanks,
Anton.