linux-kernel - Re: [PATCH 00/19] irqchip: atmel-aic: make unified AIC driver

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Date:	Wed, 6 Jan 2016 14:49:47 +0000
From:	Jason Cooper <jason@...edaemon.net>
To:	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	Milo Kim <milo.kim@...com>, tglx@...utronix.de,
	marc.zyngier@....com, alexandre.belloni@...e-electrons.com,
	ludovic.desroches@...el.com, nicolas.ferre@...el.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/19] irqchip: atmel-aic: make unified AIC driver

Hey Milo,

On Wed, Jan 06, 2016 at 10:07:55AM +0100, Boris Brezillon wrote:
> On Wed, 6 Jan 2016 16:48:23 +0900 Milo Kim <milo.kim@...com> wrote:
> > On 01/04/2016 06:02 PM, Boris Brezillon wrote:
> > > On Mon, 4 Jan 2016 13:28:24 +0900 Milo Kim <milo.kim@...com> wrote:
> > >
> > >> This patch-set provides unified Atmel AIC (Advanced Interrupt Controller)
> > >> driver. Currently, there are two AIC drivers, AIC and AIC5.
> > >> Each driver consists of chip specific part (irq-atmel-aic.o or
> > >> irq-atmel-aic5.o) and shared code (irq-atmel-aic-common.o).
> > >> But consolidated AIC driver is just one file driver which supports both
> > >> IRQ chip systems.
> > >
> > > Sorry, but what's the real motivation behind this rework?
> > 
> > During my driver development on Atmel boards, I just found major 
> > difference between two IRQ chips is how to select HW IRQ number. Other 
> > parts could be merged into single driver like OMAP.
> 
> Except that this major difference is a central aspect, and if you look
> at your changes, you'll see that you're introducing
> 'if (aic_is_ssr_used())' statements in pretty much all irqchip
> callbacks.
> 
> As I said, I'm not against code factorization, but it's not really
> one to me, because you're adding extra conditional path all over the
> code to differentiate the two chips, which means those are not so
> similar
...
> > > Before reviewing the remaining patches, I'd like to know more about your
> > > real motivations for pushing those changes?
> > 
> > Yeap, thanks for your time. My idea is simple.
> > 
> > "Different IRQ chip operation can be consolidated if simple data 
> > structure is used."
> 
> As pointed, I don't think that's a good idea, but let's see what others
> say.
> Thomas, Jason, any comments?

I'm with Nicolas on this one.  I appreciate the effort, but it's best to
discuss the proposal with at91/irqchip maintainers prior to investing so
much effort.

sorry,

Jason.
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