linux-kernel - Re: [patch 2.6.20-rc1 4/6] PXA GPIO wrappers

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Message-ID: <458AEF79.5030600@billgatliff.com>
Date:	Thu, 21 Dec 2006 14:32:57 -0600
From:	Bill Gatliff <bgat@...lgatliff.com>
To:	Nicolas Pitre <nico@....org>
CC:	pHilipp Zabel <philipp.zabel@...il.com>,
	David Brownell <david-b@...bell.net>,
	Andrew Morton <akpm@...l.org>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Andrew Victor <andrew@...people.com>,
	Haavard Skinnemoen <hskinnemoen@...el.com>,
	Kevin Hilman <khilman@...sta.com>,
	Russell King <rmk@....linux.org.uk>,
	Tony Lindgren <tony@...mide.com>
Subject: Re: [patch 2.6.20-rc1 4/6] PXA GPIO wrappers

Guys:

>>Probably? What I am wondering is this: can the compiler
>>optimize away the range check that is duplicated in GPSR/GPCR
>>and  GPIO_bit for __gpio_set/get_value? Or could we optimize
>>this case by expanding the macros in place (which would mean
>>duplicating code from pxa-regs.h)...
>>    
>>

Who cares?  :)

I don't think there's much point in optimizing here, since these 
functions won't be hot paths anyway.  Yes, they'll be called in 
interrupt handlers and so we don't want them to be _too_ heavy, but 
compared to the overhead of an interrupt handler, a few extra 
instructions in the GPIO access will get lost in the noise.

Inlines generally seem to be more maintainable, give you a symbol that 
you can disassemble and breakpoint, etc.  I'll take them over the macro 
implementations any day, in this case even if there's a cost of a few 
instructions.

All IMHO, of course.

b.g.

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

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