linux-kernel - Re: [PATCHv3 0/7] gpio: extend basic_mmio

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Date:	Wed, 4 May 2011 15:57:25 +0100
From:	Jamie Iles <jamie@...ieiles.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Jamie Iles <jamie@...ieiles.com>,
	Anton Vorontsov <cbouatmailru@...il.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	linux-kernel@...r.kernel.org, linux@....linux.org.uk,
	tglx@...utronix.de, arnd@...db.de, nico@...xnic.net
Subject: Re: [PATCHv3 0/7] gpio: extend basic_mmio_gpio for different
 controllers

Hi Alan,

On Wed, May 04, 2011 at 03:44:40PM +0100, Alan Cox wrote:
> > OK, so here's what I've got so far (patches attached).  I've updated the 
> > basic_mmio_gpio library with your initial lkml patch and updated it to 
> > allow bgpio_chip to be embedded in another structure.  I've also 
> > attempted to convert over the bt8xx and langwell drivers but they're a 
> > little rough around the edges in places (and untested as I don't have 
> > the hardware).
> 
> Looking at the Langwell driver you replace 130 lines of code that do the
> job, with 126 lines of code that do setup for a whole extra module which
> makes it bigger and slower as well as much harder to maintain.
> 
> That sounds to me like for Langwell at least it is not worth doing
> because all you've done is added complexity, indirection and overhead. So
> NAK the Langwell one.

I picked that one because I thought it might convert nicely, but it 
didn't!  I posted it anyway in case I'm missing a better way to do it 
and to give a fair representation.

With regards to the ARM drivers, lots of these aren't currently devices 
(in the driver model) so converting many of these would be net code 
increase but I suspect that it's probably worth it in these cases 
(providing that's the only complexity).

> The bt8xx looks a nice example of one of the cases where it will help
> however.

Yes, and I suspect there are a few others too.

Jamie
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