linux-kernel - Re: [PATCH] USB: gadget driver for LPC32xx

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Date:	Tue, 20 Mar 2012 13:01:49 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	Roland Stigge <stigge@...com.de>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	w.sang@...gutronix.de, kevin.wells@....com,
	linux-arm-kernel@...ts.infradead.org, arm@...nel.org,
	srinivas.bakki@....com
Subject: Re: [PATCH] USB: gadget driver for LPC32xx

On Monday 19 March 2012, Roland Stigge wrote:
> Hi Arnd,
> 
> On 19/03/12 22:30, Arnd Bergmann wrote:
> > There is already a driver for the isp1301 otg part in the kernel, I don't
> > think we want to add another one.
> > 
> > From what I can tell, this shares a common ancestry with the omap version
> > but has diverged quite a bit. The best solution would really be to
> > bring the two back together and let them share a common base driver,
> > with the lpc32xx and omap specific bits in another file.
> 
> Yes, it's a good idea to share code where possible and consolidate into
> one driver.
> 
> Please consider:
> 
> The LPC32xx driver is actually using only 3 functions via isp1301:
> 
> isp1301_udc_configure()
> isp1301_set_powerstate()
> isp1301_pullup_set()
> 
> The first of those is LPC32xx specific. The power setting function is
> also done differently in isp1301_omap's power_up()/power_down() ("board
> specific"). For the pullups, there is not (yet?) a dedicated API in the
> OMAP driver, but it's really only two small I2C commands.
> 
> Are you still sure it's worth it to use a common driver when there is
> hardly shared code?

No, I guess I should have looked closed. I found a few common functions
and assumed that this would be the same driver.

> Maybe the right thing is a common low-level isp1301 interface defining
> all the registers and providing low-level (I2C) access functions,
> leaving all the "higher level"/"board specific" functions up to the
> existing drivers?
> 
> (I guess you meant drivers/usb/otg/isp1301_omap.c ?)

Yes, that sounds like a very good idea. Can you describe which part of
the function isp1301 does? It's not clear how the layering between
that and the platform driver should end up.

	Arnd
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