linux-kernel - Re: [PATCH 3/6 v9] gpio: Add userland device interface to block GPIO

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Date:	Wed, 05 Dec 2012 23:20:57 +0100
From:	Roland Stigge <stigge@...com.de>
To:	Wolfgang Grandegger <wg@...ndegger.com>
CC:	gregkh@...uxfoundation.org, grant.likely@...retlab.ca,
	linus.walleij@...aro.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, w.sang@...gutronix.de,
	jbe@...gutronix.de, plagnioj@...osoft.com, highguy@...il.com,
	broonie@...nsource.wolfsonmicro.com, daniel-gl@....net,
	rmallon@...il.com, tru@...k-microwave.de, sr@...x.de
Subject: Re: [PATCH 3/6 v9] gpio: Add userland device interface to block GPIO

Hi Wolfgang,

On 05/12/12 20:01, Wolfgang Grandegger wrote:
>> +	for (i = 0; i < block->ngpio; i++) {
>> +		status = gpio_request(block->gpio[i], "gpioblock dev");
> 
> You could use the name of the GPIO block.

OK.

>> +		if (status)
>> +			goto err1;
>> +
>> +		irq = gpio_to_irq(block->gpio[i]);
>> +		if (irq >= 0 &&
>> +		    !test_bit(FLAG_IS_OUT, &gpio_desc[block->gpio[i]].flags) &&
>> +		    !gpio_block_is_irq_duplicate(block, i)) {
>> +			status = request_irq(irq, gpio_block_irq_handler,
>> +					     IRQF_TRIGGER_FALLING,
>> +					     block->name, block);
>> +			if (status)
>> +				goto err2;
>> +
>> +			block->irq_controlled = true;
>> +		}
>> +	}
> 
> There is no need to request IRQs if "O_NONBLOCK" is specified.

Sure? Regarding this, I found: "The poll() function shall not be
affected by the O_NONBLOCK flag." [1]

> I observed that the read returns once immediately (without blocking)
> after reboot. I did not look into that yet.

Didn't happen to me. Can you tell how this can be reproduced?

Thanks,

Roland


[1] http://pubs.opengroup.org/onlinepubs/009695399/functions/poll.html
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