linux-kernel - Re: [PATCH v4 08/12] gpio: add ti-ssp gpio driver

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Date:	Tue, 9 Nov 2010 23:23:10 -0700
From:	Grant Likely <grant.likely@...retlab.ca>
To:	David Brownell <david-b@...bell.net>
Cc:	davinci-linux-open-source@...ux.davincidsp.com,
	broonie@...nsource.wolfsonmicro.com, linux-kernel@...r.kernel.org,
	rpurdie@...ys.net, Cyril Chemparathy <cyril@...com>,
	spi-devel-general@...ts.sourceforge.net,
	linux-arm-kernel@...ts.infradead.org, lrg@...mlogic.co.uk
Subject: Re: [PATCH v4 08/12] gpio: add ti-ssp gpio driver

On Tue, Nov 09, 2010 at 10:16:22PM -0800, David Brownell wrote:
> 
> > I thought the point of this device was that a single [SSP] device
> > hosted a
> > pair of multi-function serial interfaces, with each
> > implementing a
> > separate function.
> 
> function chosen based on what the board needs.
> Codec interface, SPI, GPIO, etc.
> 
>   If so, then it makes sense for the
> > base driver to
> > register child devices of the appropriate kinds.
> 
> I'd normally say board setup registers them; a
> "core"driver can't know what children would be needed.
> 
> But the point I was making was about code factoring
> not driver setup.  When  the functions don't have
> much commonality, they might as well just write to
> the relevant registers instead of expecting to have
> a non-register programming interface (of dubious
> generality of a "core" driver, but much complexity).
> 
> Easier just to have children use registers directly,
> in several similar cases.  Less overhead, too.

I guess it depends on how much overlap/interlock there is between the
multiple channels.  If there is shared context, then that is a
stronger argument for a shared api.  Cyril, what say you?

g.

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