linux-kernel - Re: [PATCH] gpio: twl4030: Correct status reporting when the GPIO is used as output

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Message-ID: <50C07984.8000003@ti.com>
Date:	Thu, 6 Dec 2012 11:55:00 +0100
From:	Peter Ujfalusi <peter.ujfalusi@...com>
To:	Grant Likely <grant.likely@...retlab.ca>
CC:	Linus Walleij <linus.walleij@...aro.org>,
	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>
Subject: Re: [PATCH] gpio: twl4030: Correct status reporting when the GPIO
 is used as output

On 12/05/2012 11:48 PM, Grant Likely wrote:
>> -	base = REG_GPIODATAIN1 + d_bnk;
>> +	direction = gpio_twl4030_read(REG_GPIODATADIR1 + d_bnk);
>> +	if (direction > 0 && (direction >> d_off) & 0x1)
>> +		base = REG_SETGPIODATAOUT1 + d_bnk;
>> +	else
>> +		base = REG_GPIODATAIN1 + d_bnk;
>> +
> 
> This is probably quite expensive considering that reads need to go out
> the i2c bus. Things like the output state and the pin direction should
> be cached by the driver in its private data structure so that you don't
> add an additional i2c round trip.

True. I have sent the v2, which grown a bit since I did not wanted to add more
global variable to this driver.

-- 
Péter
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