linux-kernel - Re: Adding USB charge current property in the Linux Battery core

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Message-ID: <20111109121950.GB16315@legolas.emea.dhcp.ti.com>
Date:	Wed, 9 Nov 2011 14:19:52 +0200
From:	Felipe Balbi <balbi@...com>
To:	Ashish Jangam <Ashish.Jangam@...tcummins.com>
Cc:	"balbi@...com" <balbi@...com>,
	"linaro-dev@...ts.linaro.org" <linaro-dev@...ts.linaro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"arnd@...db.de" <arnd@...db.de>,
	"eric.miao@...aro.org" <eric.miao@...aro.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	"david-b@...bell.net" <david-b@...bell.net>
Subject: Re: Adding USB charge current property in the Linux Battery core

On Wed, Nov 09, 2011 at 12:13:14PM +0000, Ashish Jangam wrote:
> 
> > -----Original Message-----
> > From: Felipe Balbi [mailto:balbi@...com]
> > Sent: Wednesday, November 09, 2011 1:50 PM
> > To: Ashish Jangam
> > Cc: linaro-dev@...ts.linaro.org; linux-kernel@...r.kernel.org;
> > arnd@...db.de; eric.miao@...aro.org; Mark Brown
> > Subject: Re: Adding USB charge current property in the Linux Battery core
> > 
> > Hi,
> > 
> > On Wed, Nov 09, 2011 at 01:43:37PM +0530, ashishj3 wrote:
> > > For a better performance in USB charging operation, the DA9052/53
> > charging
> > > current can be configured in accordance with the USB host current
> > > delivering capacity (known through USB drivers negotiation).
> > >
> > > To implement this useful feature, a new writable property "USB charge
> > current"
> > > needs to be added in the Linux battery core.
> > >
> > > Let me know your views on it.
> > 
> > that's the wrong way to do it. What we need is to use the transceiver
> > notifications to notify every time someone calls usb_gadget_vbus_draw()
> > and pass the mA parameter as argument to the event notification.
> > 
> 
> This means that we need to modify the function usb_gadget_vbus_draw()
> to add a call like blocking_notifier_call_chain() but will this be fine with
> the usb gadget driver maintainers?

I am the USB gadget driver maintainer and I have plans to do that
myself. First thing we need to do is convert the final UDC drivers to
the udc Class which I wrote and Sebastian helped brushing it up, then we
uninline the usb_gadget_* wrappers and move them to
drivers/usb/gadget/udc-core.c, then we can move the transceiver notifier
to the UDC as it makes more sense, and convert blocking into atomic
notifier.

After that we can add notifications to all gadget events/API/etc...

-- 
balbi

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