linux-kernel - Re: [RFC][PATCH 0/3] add EXTCON_CHG_USB

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Date:   Wed, 17 May 2017 09:12:42 -0400
From:   Damien Riegel <damien.riegel@...oirfairelinux.com>
To:     linux-usb@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        kernel@...oirfairelinux.com
Subject: Re: [RFC][PATCH 0/3] add EXTCON_CHG_USB_* cables to MSM USB phy

Hi,

On Fri, Apr 14, 2017 at 02:43:27PM -0400, Damien Riegel wrote:
> This patchset adds a way for the MSM USB phy to notify a power supply
> when the charging state changes. It achieves that using the extcon
> subsystem.
> 
> The first patch makes sure msm_otg_notify_charger is called after the
> charger attributes have been set.
> The second one makes sure that function is called when unplugging a
> "in-the-wall" charger.
> The last one adds EXTCON_CHG_USB_* cables to the phy.
> 
> 
> I send this patchset as RFC because it seems a bit peculiar to have
> different drivers that generate the EXTCON_USB_* and EXTCON_CHG_USB_*
> events, so I want to make sure to get things right.
> 
> As far as I can tell, all the drivers in the kernel that have USB
> charger events also have the EXTCON_USB one. In this case, this patchset
> would make things a bit different for the MSM phy:
> 
>        +----------+      +--------------+
>        |   gpio   |      |     PMIC     |<-+
>        +----------+      +--------------+  |
>            |                    |          |
>            `--------------------+          |  EXTCON_CHG_USB_*
>                                 |          |       events
>                     EXTCON_USB  |          |
>                       events    |          |
>                                \|/         |
>                          +--------------+  |
>                          |   USB PHY    |--+
>                          +--------------+
>        
> Text version: EXTCON_USB comes from a GPIO or a PMIC, that triggers a
> notifier in the USB phy. That notifier will determine the new
> EXTCON_CHG_USB_XXX state and the PMIC will be notified about it and
> determine how much current it can use to charge a battery.
> 
> Please let me know if this is the correct way to go.

I wanted to know if someone has any comment to make on this patchset?
I'm currently working on the PMIC driver and it uses the EXTCON
notifications, so I just want to make sure it makes sense to do that.

Thanks,
-- 
Damien