linux-kernel - Re: [PATCH] power_supply: Add driver for TWL4030/TPS65950 BCI charger

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Date:	Thu, 10 Dec 2009 18:51:06 +0200
From:	Felipe Balbi <felipe.balbi@...ia.com>
To:	ext Anton Vorontsov <avorontsov@...mvista.com>
Cc:	"Balbi Felipe (Nokia-D/Helsinki)" <felipe.balbi@...ia.com>,
	Grazvydas Ignotas <notasas@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Madhusudhan Chikkature <madhu.cr@...com>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>
Subject: Re: [PATCH] power_supply: Add driver for TWL4030/TPS65950 BCI
 charger

Hi,

On Thu, Dec 10, 2009 at 03:44:11PM +0100, ext Anton Vorontsov wrote:
>Yep. The only thing I'm afraid of is that once the driver is in,
>then nobody will bother with improving it to do the right thing.
>But an imperfect driver is better than none.

I'm currently implementing the notifier part in a generic manner that 
would handle all transceivers (well, they would have to provide a some 
implementations for function pointers in struct otg_transceiver).

Then drivers like twl4030-bci and musb_hdrc could register for 
notifications from the transceiver. I was thinking of notifying the 
following events:

enum usb_xceiv_events {
	USB_EVENT_NONE,		/* no events or cable disconnected */
	USB_EVENT_VBUS,		/* vbus valid event */
	USB_EVENT_ID,		/* id was grounded */
	USB_EVENT_CHARGER,	/* usb dedicated charger */
	USB_EVENT_ENUMERATED,	/* gadget driver enumerated */
};

for the USB_EVENT_ENUMERATED we could also pass the bMaxPower (in mA) 
field of the struct usb_configuration, then BCI (or bq24xxx for that 
matter) can configure that as input current for charging.

USB_EVENT_ID is necessary because in most boards (at least the ones I've 
seen) the charging chip (bq24xxx) also plays the role as charge pump, 
sourcing vbus on OTG sessions.

USB_EVENT_VBUS and USB_EVENT_CHARGER aren't necessary on all cases, but 
boards like RX-51 where it has a different transceiver for charger 
detection, it's necessary to have those two separated.

If you guys have any comments already, please comment :-)

I'll try to finish a prototype by tomorrow and try to send it as RFC.
Will be sure to Cc you Anton.

-- 
balbi
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