linux-kernel - Re: [PATCH] cs5535_gpio: gpio_chip.get should return the input value

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Message-ID: <808c8e9d1002241952s63633da3m471b6fb170558789@mail.gmail.com>
Date:	Wed, 24 Feb 2010 21:52:07 -0600
From:	Ben Gardner <gardner.ben@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andres Salomon <dilinger@...labora.co.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cs5535_gpio: gpio_chip.get should return the input value

>> --- linux-2.6.33-rc8.orig/drivers/gpio/cs5535-gpio.c
>> +++ linux-2.6.33-rc8/drivers/gpio/cs5535-gpio.c
>> @@ -154,7 +154,7 @@
>>
>>  static int chip_gpio_get(struct gpio_chip *chip, unsigned offset)
>>  {
>> -     return cs5535_gpio_isset(offset, GPIO_OUTPUT_VAL);
>> +     return cs5535_gpio_isset(offset, GPIO_READ_BACK);
>>  }
>>
>>  static void chip_gpio_set(struct gpio_chip *chip, unsigned offset, int val)
>
> <presses F10>
>
> What were the user-visible effects of this bug?

The user-visible effects were that the input didn't work.
I use the CS5535 chip in a custom board that uses GPIO 25 and 26 as
voltage monitoring inputs (external voltage comparators).
Since the char-based cs5535-gpio is now deprecated, I'm trying out the
gpio driver.
I export the GPIO pins via sysfs to access them from user-space.
Reading the 'value' member didn't reflect the input.

Personally, I would prefer a separate sysfs entry for the output and
the input, since the GPIO pins can be both outputs and inputs, but
that would require a gpiolib change.
Since there doesn't appear to be a gpio maintainer, any change to that
might be tricky.

Ben
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