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

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

[MyungJoo Ham]

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Anton Vorontsov wrote:
> 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.
> 
> 


The "RFC" patch for this feature is now shown at:
http://git.kernel.org/?p=linux/kernel/git/mzx/extcon.git;a=commit;h=5655aeef83addaec77a3b9387a3dd18b6c146dd5
(Note that "for-add-feature" branch is sort of "RFC" branch)

I'm now considering relaying notifications of data updates possible via
the notifier block of register-interest. Any inputs are welcomed.


Anyway, for the USB issue of "suspend/resume at host-side and current-limit at
device-side", we will need to
1. update regulator subsystem to have notification for current change
(it does for enable/disable/voltage-changes)
2. let the charger use current-regulator
3. let the one who detects (usb driver?) changes at host-side change the
current limit of that current-regulator
4. let the event from current-regulator relayed via extcon.
We may use power-supply class as well for this issue. (may need to update
if power-supply class does not have notifications and suspend/resume states)


Cheers,
MyungJoo

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

[Tc, Jenny]

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> The "RFC" patch for this feature is now shown at:
> http://git.kernel.org/?p=linux/kernel/git/mzx/extcon.git;a=commit;h=5655a
> eef83addaec77a3b9387a3dd18b6c146dd5
> (Note that "for-add-feature" branch is sort of "RFC" branch)
> 
> I'm now considering relaying notifications of data updates possible via the
> notifier block of register-interest. Any inputs are welcomed.
> 
> 
> Anyway, for the USB issue of "suspend/resume at host-side and current-limit
> at device-side", we will need to 1. update regulator subsystem to have
> notification for current change (it does for enable/disable/voltage-changes)
> 2. let the charger use current-regulator 3. let the one who detects (usb
> driver?) changes at host-side change the current limit of that current-
> regulator 4. let the event from current-regulator relayed via extcon.
> We may use power-supply class as well for this issue. (may need to update if
> power-supply class does not have notifications and suspend/resume states)
> 

For this solution to work, the cable provider itself
need to register with any of these subsystems - power_supply/regulator/charger manager
IMHO a cable provider shouldn't register itself with any of the subsystem.

 For example it cannot register with power_supply subsystem
since it's not a power_supply. It's just source for a power_supply.
We register either charger/battery with power supply. I couldn't find a way
to register the cable with power supply subsystem. 

Anton,
Do you have any suggestion here?

I think the same case with regulator framework also. A cable doesn¡¯t belong
to a regulator framework. A cable doesn¡¯t expose any control attribute (current control/voltage
control). It just have  properties (eg current) controlled by external agents (Host machine/wall charger)

And charger manager is a consumer and not a provider. It cannot decide the charger cable capabilities.

I  have a modified version of the above patch which uses properties directly. 
https://gitorious.org/linux-charging-framework/linux-charging-framework/commit/ff358373dcb32027ebe1a267fc8b8999a3bd37e4

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

[Anton Vorontsov]

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On Thu, Nov 22, 2012 at 01:00:52PM +0000, Tc, Jenny wrote:
[...]
> For this solution to work, the cable provider itself
> need to register with any of these subsystems - power_supply/regulator/charger manager
> IMHO a cable provider shouldn't register itself with any of the subsystem.
> 
>  For example it cannot register with power_supply subsystem
> since it's not a power_supply. It's just source for a power_supply.
> We register either charger/battery with power supply. I couldn't find a way
> to register the cable with power supply subsystem.

Yes, I guess that doesn't make much sense.

> Anton,
> Do you have any suggestion here?
> 
> I think the same case with regulator framework also. A cable doesn¡¯t belong
> to a regulator framework. A cable doesn¡¯t expose any control attribute (current control/voltage
> control). It just have  properties (eg current) controlled by external agents (Host machine/wall charger)
> 
> And charger manager is a consumer and not a provider. It cannot decide the charger cable capabilities.
> 
> I  have a modified version of the above patch which uses properties directly. 
> https://gitorious.org/linux-charging-framework/linux-charging-framework/commit/ff358373dcb32027ebe1a267fc8b8999a3bd37e4

(Please, always inline the patches.)

I spent some time trying to understand what exactly you're trying to
accomplish and I failed, and that's why:

1. I see only some small snippets of the code, sometimes by means of URLs
   and references to another patches, which is hard to follow when you
   have like tens of emails in the thread;
2. I believe I still didn't see a user of this callback.

So, basically you're trying to force me to read your mind and guess your
ideas, but as it appears, I'm not good at it. :)

So, please do the following:

- Prepare a complete, but minimal workable solution, a patchset that shows
  how exactly you use the new features that you introduce;

- The series must be an all-in-1 patchset, so people won't need to go back
  and forth trying to understand how things depend on each other;

- Briefly describe how things work, a typical use-case and how drivers
  interact with each other. E.g. which driver registers extcon_device,
  which driver reads mA field, which driver sets mA field (and based on
  what information), which driver listens for the extcon events, which
  driver produces the extcon events, etc. No need for lengthy explanations
  about why you made the decisions, just a brief explanation of how things
  currently work and interact.

Thanks,
Anton.

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

[MyungJoo Ham]

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> > >>>>>> I think that the role of extcon subsystem notify changed
> > >>>>>> state(attached/detached) of cable to notifiee, but if you want to
> > >>>>>> add property feature of cable, you should solve ambiguous issues.
> > >>>>>>
> > >>>>>> First,
> > >>>>>> This patch only support the properties of charger cable but,
> > >>>>>> never support property of other cable. The following structure
> > >>>>>> depend on only charger cable. We can check it the following
> > structure:
> > >>>>>>   struct extcon_chrg_cbl_props {
> > >>>>>>           enum extcon_chrgr_cbl_stat cable_state;
> > >>>>>>           unsigned long mA;
> > >>>>>>   };
> > >>>>>>
> > >>>>>> I think that the patch have to support all of cables for property
> > >> feature.
> > >>>>>
> > >>>>> My suggestion is to have a structure like this
> > >>>>>
> > >>>>> struct  extcon_cablel_props {
> > >>>>>     unsigned int cable_state;
> > >>>>>             unsigned int data;
> > >>>> Why can't it be float/long/double??
> > >>>>> }
> > >>>>> Not all cables will have more than two states. If any cable has
> > >>>>> more than two states, the above structure makes it flexible to
> > >>>>> represent additional state and the data associated
> > >>>>>
> > >>>>>>
> > >>>>>> Second,
> > >>>>>> Certainly, you should define common properties of all cables and
> > >>>>>> specific properties of each cable. The properties of charger
> > >>>>>> cable should never be defined only.
> > >>>> IMHO the extcon doesn't know anything about the cable except the
> > >>>> state which is currently it is in and which also is set by the
> > >>>> provider.I am unable to understand why should extcon provide more
> > >>>> than what it knows?It should just limit itself to broadcasting the
> > >>>> cable state and exploiting it for any other information would only
> > >>>> lead to
> > >> more un-necessary code.
> > >>>> It should be same as IIO subsystem where the consumer and provider
> > >>>> knows before hand what information they are going to share and with
> > >>>> what precision and IIO core is just a way to do that.It doesn't
> > >>>> know anything beyond what is given by the provider.
> > >>>> Same is the case with driver core where individual driver sets it's
> > >>>> own private data and the driver core just gives that private data
> > >>>> back to the driver as and when it needs but parsing the private
> > >>>> data in the right way is up to the individual driver.
> > >>>>
> > >>>> I fail to understand why is not the case here.
> > >>>
> > >>> The requirement is different from the IIO case. I am trying to
> > >>> extend the Power Supply class to support charging in a generic way
> > >> (https://lkml.org/lkml/2012/10/18/219).
> > >>> The extcon consumer in this case is not a device driver. It's part
> > >>> of power
> > >> supply class driver itself.
> > >>> I am open to any solution to get the cable properties dynamically.
> > >>> Do you find a better but generic mechanism for this?
> > >>>
> > >>> I am trying to extend  extcon just because I couldn¡¯t find any other
> > >>> subsystem which gives cable notifications. IMHO, it's good if we can
> > >>> avoid consumer and provider driver level dependencies just by
> > >>> extending extcon. This will ensure that the same driver will work on
> > >>> any
> > >> platform as long as it's having the dependency only on extcon.
> > >>> We shouldn't put any driver level dependency between extcon
> > consumer
> > >> and provider.
> > >>> When we do like that, the extcon consumer is expecting the similar
> > >>> implementation for the provider on all platforms. This may not be
> > >>> possible
> > >> Is there anything wrong in assuming similar implementation for all
> > >> the providers?I think the providers know what it can provide and this
> > >> may vary quite a lot.Or can we make a generic provider driver which
> > >> will encompass all the randomness in the various provider
> > >> drivers?This generic driver will get all the properties and since it
> > >> will be generice anyone can use it to know what properties to expect.This
> > will keep the extcon design intact.
> > >
> > > Maintainer??
> > 
> > I agreed about opinion of anish singh. The extcon provider driver provide
> > generic
> > 
> > ----
> > struct  extcon_cablel_props {
> >      unsigned int cable_state;
> >      unsigned int data;
> > }
> > ----
> > You suggested upper structure and said it is only flexible to represent
> > additional state, But, it is non-standard. What store real data on "unsigned int
> > data"? It isn't determined and flexible. That is extcon consumer driver should
> > already know type of real data or value of real data. The extcon consumer
> > driver has strong dependency on extcon provider driver. In this case, if
> > extcon provider driver can change data value of "unsigned int data", extcon
> > consumer provider have to be modified according to extcon provider driver.
> > I think it isn't correct apporach. So, I proposed that we should define
> > properties for all cables.
> 
> I couldn¡¯t find properties common for all type of cables. Alternate method I can think of is
> a new driver "extcon-charger.c".  This driver will register with extcon subsystem.
> 
> The consumer and provider can use the APIs and properties exposed by this driver.  This
> way we can ensure that extcon design is intact and the additional charger cable state and
> properties can be handled by this driver. Does that make sense?

Adding another API at a device driver is something to be avoided unless it's
inevitable.

The state/status information required by a charger should be embedded in the
data structure of the charger (e.g., regulator, power-supply-class, or
charger-manager). However, we may consider bridging them via extcon anyway.

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;

Is there any problems with this approach?


If you need to embeded "current-limit" information, the regulator should be
able to provide it (current-limit regulator).
If you need to embed "suspend/resume" status information in general for a
specific cable type, you need to define corresponding data structure related
to the cable type (class) and make it connected via extcon.


> 
> > 
> > >>
> > >>> and does not seems to  be a scalable solution. IMHO, the extcon
> > >>> should provide a mechanism to retrieve the cable properties.
> > >>> Consumer drivers can use this API to get the cable properties
> > >>> without knowing the provider driver implementation. This will  make
> > >>> the extcon drivers more
> > >> scalable and reusable across multiple platforms.
> > >>>
> > >>>>>
> > >>>>> Hope above structure would be enough to represent the common
> > cable
> > >>>>> state and it's data. If a cable has more than two states, then
> > >>>>> extcon_update_state can be used to notify the consumer 1)Provider
> > >>>>> can just toggle the "state" argument to notify the consumer that
> > >>>>> cable state is changed OR
> > >>>>> 2) Add one more argument  like  extcon_update_state(struct
> > >>>>> extcon_dev *edev, u32 mask, u32 state1, u32 sate2)
> > >>>> This will cause other drivers to change such as arizona.
> > >>>>> If the state2 is set, then consumers can use
> > >>>>> get_cable_properties() to query the cable properties. State2 need
> > >>>>> to be used only if the cable need to represent more than two state
> > >>>>>
> > >>>>>>
> > >>>>>> Third,
> > >>>>>> If we finish to decide the properties for all cables, I'd like to
> > >>>>>> see a example
> > >>>> Why do we think that state and property is the only thing which the
> > >>>> consumer want to know?I am sure there would be some more
> > properties
> > >>>> which would be of some interest to consumers and there is quite a
> > >>>> possibility that in future we might get a patch for that also.So
> > >>>> instead of that limiting it to just state is a good idea.
> > >>>>>> code.
> > >>>>>
> > >>>>> Agreed. If we  agree on the above structure, I can modify the
> > >>>>> charging subsystem patch to use the same structure.
> > >>>>> (https://lkml.org/lkml/2012/10/18/219). This would give a
> > >>>>> reference for the
> > >>>> new feature.
> > >>>>>
> > >>>>>>
> > >>>>>> You explained following changed state of USB according to Host
> > >>>>>> state on other patch.
> > >>>>>> ---------------------------
> > >>>>>> For USB2.0
> > >>>>>> 1) CONNECT (100mA)->UPDATE(500mA)->DISCONNECT(0mA)
> > >>>>>> 2) CONNECT (100mA)->UPDATE(500mA)->HOST
> > >>>> SUSPEND(2.5mA/500mA)-
> > >>>>>>> DISCONNECT(0mA)
> > >>>>>> 3) CONNECT (100mA)->UPDATE(500mA)->HOST
> > >>>> SUSPEND(2.5mA/500mA)-
> > >>>>>>> HOST RESUME(500mA)->DISCONNECT(0mA)
> > >>>>>>
> > >>>>>> For USB 3.0
> > >>>>>> 4) CONNECT (150mA)->UPDATE(900mA)->DISCONNECT(0mA)
> > >>>>>> 5) CONNECT (150mA)->UPDATE(900mA)-> HOST
> > >>>> SUSPEND(2.5mA/900mA)-
> > >>>>>>> DISCONNECT(0mA)
> > >>>>>> 6) CONNECT (100mA)->UPDATE(900mA)->HOST
> > >>>> SUSPEND(2.5mA/900mA)-
> > >>>>>>> HOST RESUME(900mA)->DISCONNECT(0mA)
> > >>>>>> ---------------------------
> > >>>>>>
> > >>>>>> I have a question. Can the provider device driver(e.g.,
> > >>>>>> extcon-max77693.c/
> > >>>>>> extcon-max8997.c) detect the changed state of host? I'd like to
> > >>>>>> see the example device driver that the provider device driver
> > >>>>>> detect changed state of host.
> > >>>>>> Could you provide example device driver?
> > >>>>>
> > >>>>> Good question. The OTG drivers are capable of identifying the
> > >>>>> SUSPEND
> > >>>> event.
> > >>>>> System cannot setup SDP (USB host) charging with maximum charging
> > >>>>> current - 500mA (USB2.0/ 900mA(USB 3)) without enumerating the
> > USB.
> > >>>>> The USB enumeration can be done only with a USB/OTG driver. IMHO
> > >>>>> the above extcon drivers (extcon-max77693.c/ extcon-max8997.c) are
> > >>>>> not capable of doing the USB enumeration and identifying the
> > >>>>> charge current. They can just identify the charger type -
> > >> SDP/DCP/CDP/ACA/AC.
> > >>>>> The intelligence for USB enumeration should be inside USB/OTG
> > driver.
> > 
> 
> 
> 
> 
>        
>   
>          
> 
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RE: RE: [PATCH] extcon : callback function to read cable property

[Tc, Jenny]

Myunjoo,

Ping. Could you please have a look at my response below?

-jtc

> -----Original Message-----
> From: Tc, Jenny
> Sent: Thursday, October 25, 2012 2:55 PM
> To: myungjoo.ham@samsung.com; ???
> Cc: linux-kernel@vger.kernel.org; anish kumar
> Subject: RE: RE: [PATCH] extcon : callback function to read cable property
> 
> > Subject: Re: RE: [PATCH] extcon : callback function to read cable
> > property
> > > For charger cable the current each cable can provide will be common.
> > > But may not be relevant for other cables.
> > >
> > > I understand your point on extcon role. But my concern is, when the
> > > consumer driver gets a notification on cable state change, how does
> > > the consumer query the cable properties in a generic way. Do you
> > > have any
> > suggestions for this?
> > >
> > > A use case can be as below
> > >
> > > When a USB host cable (SDP) connected to the platform, without USB
> > > enumeration it can support only up to 100mA(USB2.)/150mA(USB 3.0)
> > > (As
> > per USB charging spec).
> > > Once the enumeration is done this can be 500mA/950mA. If the
> > > consumer charger driver need to configure the charger chip, it need
> > > to know the
> > charger cable capabilities.
> > > For example a platform PLAT1 may have charger driver CHRGR1 and OTG
> > driver OTG1.
> > > But platform PLAT2 may have CHGR1 but different OTG driver OTG2. How
> > > CHGR1 driver can detect  the cable properties without having any
> > > platform layer hooks? The platform layer hooks (using platform
> > > data)will work only if the consumer is a platform driver. What if
> > > it's a
> > framework which will have the same flow in all platforms?
> >
> > In general,
> > an extcon user (extcon notifee) knows who's the extcon notifier; the
> > user is supposed to know the name of the notifier.
> >
> > Thus, the extcon user should be able to get the appropriate object;
> > i.e., a regulator struct in this case. Then, according to the USB
> > state, the current limit of the USB can be changed by the notifier;
> > which may notify (regulator subsystem has one) the extcon user to
> > react (change current limit of
> > charger?)
> 
> The flow we have is "notifier (OTG driver/cable notifier driver) -> extcon->
> charging framework->charger driver"
> 
> When the framework gets notification from the extcon, it just know cable is
> connected/disconnected
> 
> For a USB charging the state machine can be
> 
> For USB2.0
> 1) CONNECT (100mA)->UPDATE(500mA)->DISCONNECT(0mA)
> 2)CONNECT (100mA)->UPDATE(500mA)->HOST SUSPEND(2.5mA/500mA)-
> >DISCONNECT(0mA)
> 3) CONNECT (100mA)->UPDATE(500mA)->HOST SUSPEND(2.5mA/500mA)-
> >HOST RESUME(500mA)->DISCONNECT(0mA)
> 
> For USB 3.0
> 4) CONNECT (150mA)->UPDATE(900mA)->DISCONNECT(0mA)
> 5) CONNECT (150mA)->UPDATE(900mA)-> HOST SUSPEND(2.5mA/900mA)-
> >DISCONNECT(0mA)
> 6) CONNECT (100mA)->UPDATE(900mA)->HOST SUSPEND(2.5mA/900mA)-
> >HOST RESUME(900mA)->DISCONNECT(0mA)
> 
> >
> > Anyway, in your case of PLAT2, doesn't CHGR1 has (or is) a regulator
> > controlling the charger current and if the OTG2 regulator affects the
> > behavior of CHGR1, (the current of OTG2-reg goes to CHGR1-reg) the
> > consumer- supplier chain should be setup (if the BSP is ideal).
> >
> > OR
> >
> > If it is impossible to have any objects of OTG2 (looks strange,
> > but..), you may have two cables, USB (data) and Fast-charger.04 (add
> > +400mA to USB), where Fast-charger.04 is enabled when USB2
> enumeration
> > is done with 5
> 
> I got your point. It's not just 2 cables we may need 4 cables to support USB2.0
> and USB3.0 since the charge current can be 100/500 for USB2.0 and 150/900
> for USB 3.0. But what about the states?
> 
> .
> >
> >
> >
> > However, the following callback might be considered if there are cases
> > where an extcon user has information of extcon_name and cable_name
> > while the user CANNOT get any information on which device or object is
> > related with the specific cable; in struct extcon, with optional user
> > initializing data section:
> >
> > +	struct device **cable_device;
> > OR
> > +	char **cable_device_name;
> >
> > With any relevant changes in the status with cable_device, we may
> > notify any notifier-block that are interested in the specific cable.
> > Then, the notifier- block (for register_interest) is going to handle
> > extcon-state changes and cable_device notifications.
> >
> > Currently, the user's nb is for cable attach/detach events with
> > true/false value in the place of 32bit value (val). However, if we add
> > the third possible value for that parameter
> > (0: cable detached, 1: cable attached, 2: cable status changed; go
> > find out what's going on), it is still compatible.
> >
> > I considered using a void pointer instead of cable_device, too.
> > However, that would spoil the subsystem too much; we'll be creating a
> > total
> > chaos: "USB-A driver uses struct regulator", "USB-B driver uses struct
> > device", "USB-C driver uses true/false", and so on.
> 
> But just by getting the device instance how do we extract the cable
> properties like cable state and the charge current in a generic way?
> 

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

[Tc, Jenny]

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> Subject: Re: RE: [PATCH] extcon : callback function to read cable property
> > For charger cable the current each cable can provide will be common.
> > But may not be relevant for other cables.
> >
> > I understand your point on extcon role. But my concern is, when the
> > consumer driver gets a notification on cable state change, how does
> > the consumer query the cable properties in a generic way. Do you have any
> suggestions for this?
> >
> > A use case can be as below
> >
> > When a USB host cable (SDP) connected to the platform, without USB
> > enumeration it can support only up to 100mA(USB2.)/150mA(USB 3.0) (As
> per USB charging spec).
> > Once the enumeration is done this can be 500mA/950mA. If the consumer
> > charger driver need to configure the charger chip, it need to know the
> charger cable capabilities.
> > For example a platform PLAT1 may have charger driver CHRGR1 and OTG
> driver OTG1.
> > But platform PLAT2 may have CHGR1 but different OTG driver OTG2. How
> > CHGR1 driver can detect  the cable properties without having any
> > platform layer hooks? The platform layer hooks (using platform
> > data)will work only if the consumer is a platform driver. What if it's a
> framework which will have the same flow in all platforms?
> 
> In general,
> an extcon user (extcon notifee) knows who's the extcon notifier; the user is
> supposed to know the name of the notifier.
> 
> Thus, the extcon user should be able to get the appropriate object; i.e., a
> regulator struct in this case. Then, according to the USB state, the current
> limit of the USB can be changed by the notifier; which may notify (regulator
> subsystem has one) the extcon user to react (change current limit of
> charger?)

The flow we have is "notifier (OTG driver/cable notifier driver) -> extcon->
charging framework->charger driver"

When the framework gets notification from the extcon, it just know cable is connected/disconnected

For a USB charging the state machine can be 

For USB2.0
1) CONNECT (100mA)->UPDATE(500mA)->DISCONNECT(0mA)
2)CONNECT (100mA)->UPDATE(500mA)->HOST SUSPEND(2.5mA/500mA)->DISCONNECT(0mA)
3) CONNECT (100mA)->UPDATE(500mA)->HOST SUSPEND(2.5mA/500mA)->HOST RESUME(500mA)->DISCONNECT(0mA)

For USB 3.0
4) CONNECT (150mA)->UPDATE(900mA)->DISCONNECT(0mA)
5) CONNECT (150mA)->UPDATE(900mA)-> HOST SUSPEND(2.5mA/900mA)->DISCONNECT(0mA)
6) CONNECT (100mA)->UPDATE(900mA)->HOST SUSPEND(2.5mA/900mA)->HOST RESUME(900mA)->DISCONNECT(0mA)

> 
> Anyway, in your case of PLAT2, doesn't CHGR1 has (or is) a regulator
> controlling the charger current and if the OTG2 regulator affects the behavior
> of CHGR1, (the current of OTG2-reg goes to CHGR1-reg) the consumer-
> supplier chain should be setup (if the BSP is ideal).
> 
> OR
> 
> If it is impossible to have any objects of OTG2 (looks strange, but..), you may
> have two cables, USB (data) and Fast-charger.04 (add +400mA to USB),
> where Fast-charger.04 is enabled when USB2 enumeration is done with 5

I got your point. It's not just 2 cables we may need 4 cables to support USB2.0 and USB3.0 since
the charge current can be 100/500 for USB2.0 and 150/900 for USB 3.0. But what about the states?

.
> 
> 
> 
> However, the following callback might be considered if there are cases
> where an extcon user has information of extcon_name and cable_name
> while the user CANNOT get any information on which device or object is
> related with the specific cable; in struct extcon, with optional user initializing
> data section:
> 
> +	struct device **cable_device;
> OR
> +	char **cable_device_name;
> 
> With any relevant changes in the status with cable_device, we may notify
> any notifier-block that are interested in the specific cable. Then, the notifier-
> block (for register_interest) is going to handle extcon-state changes and
> cable_device notifications.
> 
> Currently, the user's nb is for cable attach/detach events with true/false
> value in the place of 32bit value (val). However, if we add the third possible
> value for that parameter
> (0: cable detached, 1: cable attached, 2: cable status changed; go find out
> what's going on), it is still compatible.
> 
> I considered using a void pointer instead of cable_device, too.
> However, that would spoil the subsystem too much; we'll be creating a total
> chaos: "USB-A driver uses struct regulator", "USB-B driver uses struct
> device", "USB-C driver uses true/false", and so on.

But just by getting the device instance how do we extract the cable properties like
cable state and the charge current in a generic way?


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

[MyungJoo Ham]

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> 
> > Subject: Re: [PATCH] extcon : callback function to read cable property
> > 
> > On 10/19/2012 12:13 PM, Tc, Jenny wrote:
> > The rold of extcon inform only attached/detached state of extcon consumer
> > driver from extcon provider driver. After extcon consumer driver detect the
> > state of cable through extcon, extcon consumer driver or framework should
> > get the additional information of cable from other device driver except of
> > extcon.
> > 
> > Also, extcon manage various cables (e.g., USB, TA, MHL, JIG-USB-ON, JIG-
> > USB-OFF, Dock) What are common properties among many cables expect
> > attached or detached state?
> > 
> 
> For charger cable the current each cable can provide will be common.
> But may not be relevant for other cables. 
> 
> I understand your point on extcon role. But my concern is, when the consumer
> driver gets a notification on cable state change, how does the consumer query the
> cable properties in a generic way. Do you have any suggestions for this?
> 
> A use case can be as below
> 
> When a USB host cable (SDP) connected to the platform, without USB enumeration
> it can support only up to 100mA(USB2.)/150mA(USB 3.0) (As per USB charging spec).
> Once the enumeration is done this can be 500mA/950mA. If the consumer charger driver
> need to configure the charger chip, it need to know the charger cable capabilities.
> For example a platform PLAT1 may have charger driver CHRGR1 and OTG driver OTG1.
> But platform PLAT2 may have CHGR1 but different OTG driver OTG2. How 
> CHGR1 driver can detect  the cable properties without having any platform layer
> hooks? The platform layer hooks (using platform data)will work only if the consumer is
> a platform driver. What if it's a framework which will have the same flow in all platforms?

In general,
an extcon user (extcon notifee) knows who's the extcon notifier; the user
is supposed to know the name of the notifier.

Thus, the extcon user should be able to get the appropriate object; i.e.,
a regulator struct in this case. Then, according to the USB state,
the current limit of the USB can be changed by the notifier; which
may notify (regulator subsystem has one) the extcon user to react
(change current limit of charger?)

Anyway, in your case of PLAT2, doesn't CHGR1 has (or is) a regulator
controlling the charger current and if the OTG2 regulator affects
the behavior of CHGR1, (the current of OTG2-reg goes to CHGR1-reg)
the consumer-supplier chain should be setup (if the BSP is ideal).

OR

If it is impossible to have any objects of OTG2 (looks strange, but..),
you may have two cables, USB (data) and Fast-charger.04 (add +400mA to USB),
where Fast-charger.04 is enabled when USB2 enumeration is done with 5.



However, the following callback might be considered if there are cases where
an extcon user has information of extcon_name and cable_name while the user
CANNOT get any information on which device or object is related with the
specific cable; in struct extcon, with optional user initializing data section:

+	struct device **cable_device;
OR
+	char **cable_device_name;

With any relevant changes in the status with cable_device,
we may notify any notifier-block that are interested in the specific
cable. Then, the notifier-block (for register_interest) is going to
handle extcon-state changes and cable_device notifications.
Currently, the user's nb is for cable attach/detach events with
true/false value in the place of 32bit value (val). However,
if we add the third possible value for that parameter
(0: cable detached, 1: cable attached, 2: cable status changed;
go find out what's going on), it is still compatible.

I considered using a void pointer instead of cable_device, too.
However, that would spoil the subsystem too much; we'll be creating
a total chaos: "USB-A driver uses struct regulator", "USB-B driver
uses struct device", "USB-C driver uses true/false", and so on.


Cheers,
MyungJoo


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

[Tc, Jenny]

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> > > > > Subject: Re: [PATCH] extcon : callback function to read cable
> > > > > property
> > > > >
> > > > > I think the reason why we have extcon is in first place is to
> > > > > only notify the clients of cable connection and disconnection
> > > > > and it is up to the client to decide what else to do with the
> > > > > cable such as finding which state it is in and other details.
> > > > > So I feel this should not be handled in the extcon.
> > > > >
> > > > > However it is up to the maintainer to decide.
> > > >
> > > > Once the consumer gets the notification, it needs to take some action.
> > > > One of the action is to read the cable properties. This can be
> > > > done by proprietary calls which is known both to the consumer and the
> provider.
> > > > My intention is to avoid this proprietary calls. Since both the
> > > > provider and consumer are communicating with the extcon subsystem
> > > > , I feel having a callback function of this kind would help to
> > > > avoid the use of proprietary calls. Also I agree that extcon
> > > > notifier chains are used to notify the cable state
> > > > (attach/detach). But if a cable has more than two states (like the
> > > > charger cable) how do we support it without
> > > having a callback function like this?
> > > > Let the maintainer take the final decision.
> > > Well this use case will keep on growing if we start factor in this
> > > kind of changes and that is why I am opposed to adding any other state.
> > > Maintainer?
> > > >
> > > >
> > >
> 
> Hello,
> 
> 
> I don't think it's appropriate to declare the charger specific properties in
> extcon.h. The status of a charger should be and can be represented by an
> instance of regulator, power-supply-class, or charger-manager.
> 
Agreed. We can move this to power supply subsystem.

> Thus, we may (I'm still not sure) need to let extcon to relay the instance
> (struct device? or char *devname?) with some callback similar with
> get_cable_device().  However, allowing (and encouraging) to pass void
> pointer of cable_props to extcon users from extcon device appears not
> adequete. If the both parties can use their own "private"
> data structure, why they cannot simply pass their own data witht the
> "private" data channel?
> 
> 
> Recap:
> - The later part of patch: NACK
> - The first part of patch (callback): need to reconsider the data type.
> We may get device pointer or device name that is correspondant to the
> cable, which in turn, guides us to the corresponding data structure (charger-
> manager, regulator, or something) However, I'm still not sure which should
> be appropriate for this.
> 

The requirement for this feature came from the implementation of the
power supply charging framework (http://www.spinics.net/lists/kernel/msg1420500.html 
refer charger_cable_event_worker function). The charging framework is not a driver. It can
be compiled with the power supply class driver to support charging. Also the
private data structure may not provide a generic method for this implementation
since the extcon provider drivers will be different in different platforms. So it's not
necessary that the framework knows the private data structure of the provider.
Basically the requirement is to have a generic method to retrieve the cable properties without
knowing the extcon provider driver internal implementation. Can you suggest a generic approach
for this problem?

Also the cable states we support in extcon (attach/detach) is not sufficient
to support the cable states of a charger cable which can have more than 2 states. The charger cable 
states can be (1)attach/(2)detach, (3)suspend - host suspend (different from detach since it's possible to charge
in this state but with a different charge current than the attached state),(4)resume - resume after the suspend,
(5)update - update the cable properties after USB enumeration (USB cable supports 100(USB2.0)/150(USB3.0)
in an un configured state. But after enumeration it can support up to 500mA(USB 2.0)/900(USB 3.0))

Since extcon is basically intended to support the cable states, how do we support cables with
more than two states?
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Re: RE: [PATCH] extcon : callback function to read cable property

[MyungJoo Ham]

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> Myunjoo/Chanwoo
> 
> Ping...
> Could you please review this patch?
> 
> -jtc
> 
> > > > Subject: Re: [PATCH] extcon : callback function to read cable
> > > > property
> > > >
> > > > I think the reason why we have extcon is in first place is to only
> > > > notify the clients of cable connection and disconnection and it is
> > > > up to the client to decide what else to do with the cable such as
> > > > finding which state it is in and other details.
> > > > So I feel this should not be handled in the extcon.
> > > >
> > > > However it is up to the maintainer to decide.
> > >
> > > Once the consumer gets the notification, it needs to take some action.
> > > One of the action is to read the cable properties. This can be done by
> > > proprietary calls which is known both to the consumer and the provider.
> > > My intention is to avoid this proprietary calls. Since both the
> > > provider and consumer are communicating with the extcon subsystem , I
> > > feel having a callback function of this kind would help to avoid the
> > > use of proprietary calls. Also I agree that extcon notifier chains are
> > > used to notify the cable state (attach/detach). But if a cable has
> > > more than two states (like the charger cable) how do we support it without
> > having a callback function like this?
> > > Let the maintainer take the final decision.
> > Well this use case will keep on growing if we start factor in this kind of
> > changes and that is why I am opposed to adding any other state.
> > Maintainer?
> > >
> > >
> > 

Hello,


I don't think it's appropriate to declare the charger specific
properties in extcon.h. The status of a charger should be and can be
represented by an instance of regulator, power-supply-class,
or charger-manager.

Thus, we may (I'm still not sure) need to let extcon to relay
the instance (struct device? or char *devname?) with some callback
similar with get_cable_device().  However, allowing (and encouraging)
to pass void pointer of cable_props to extcon users from extcon device
appears not adequete. If the both parties can use their own "private"
data structure, why they cannot simply pass their own data witht the
"private" data channel?
 

Recap:
- The later part of patch: NACK
- The first part of patch (callback): need to reconsider the data type.
We may get device pointer or device name that is correspondant to the
cable, which in turn, guides us to the corresponding data structure
(charger-manager, regulator, or something) However, I'm still not sure
which should be appropriate for this.


Cheers!
MyungJoo
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