linux-kernel - Re: [patch/rfc 2.6.19-rc5] arch-neutral GPIO calls

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Message-ID: <4558D4E6.4020601@billgatliff.com>
Date:	Mon, 13 Nov 2006 14:26:14 -0600
From:	Bill Gatliff <bgat@...lgatliff.com>
To:	David Brownell <david-b@...bell.net>
CC:	Paul Mundt <lethal@...ux-sh.org>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>,
	Andrew Victor <andrew@...people.com>,
	Haavard Skinnemoen <hskinnemoen@...el.com>, jamey.hicks@...com,
	Kevin Hilman <khilman@...sta.com>,
	Nicolas Pitre <nico@....org>,
	Russell King <rmk@....linux.org.uk>,
	Tony Lindgren <tony@...mide.com>
Subject: Re: [patch/rfc 2.6.19-rc5] arch-neutral GPIO calls

David Brownell wrote:

>On Monday 13 November 2006 11:43 am, Bill Gatliff wrote:
>  
>
>>Maybe we should codify an approach for that now, i.e. add to the 
>>reference implementation some code that hands off out-of-range GPIO 
>>lines to a function in the machine descriptor:
>>
>>
>>+static inline int gpio_direction_input(unsigned gpio)
>>+	{ if (gpio < OMAP_MAX_ARCH_GPIO) return __gpio_set_direction(gpio, 1);
>>+	  else if(mdesc->platform_gpio_set_direction) platform_gpio_set_direction(gpio, 1); }
>>
>>
>>... conveniently neglecting the way you find mdesc.  :)
>>    
>>
>
>Nah; look at arch/arm/plat-omap/gpio.c and ignore the mess, but observe
>that what you see there is essentially a bunch of "gpio controller"
>classes using the ugly "switch(type)" dispatch scheme instead of the
>prettier "type->op()" dispatch scheme.  All that stuff needs to be
>cleaner, but for now it'd suffice to add a new FPGA typecode.
>  
>

Agreed.  But if we add to the machine descriptor, then not only do you 
not need to touch arch-omap/gpio.c, but you can take that switch 
statement out, too.  Just one less chunk of code to tweak when a new 
platform is supported.


b.g.

-- 
Bill Gatliff
bgat@...lgatliff.com

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