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

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Date:	Mon, 19 Mar 2012 23:26:21 +0100
From:	Roland Stigge <stigge@...com.de>
To:	Arnd Bergmann <arnd@...db.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

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?

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 ?)

Thanks in advance,

Roland
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