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SubjectRe: [PATCH 1/2] input: adp5588-keys - get value from data out when dir out
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On Apr 21, 2012, at 2:47, Dmitry Torokhov wrote:

> Hi Jean-François,
>
> On Fri, Apr 20, 2012 at 11:32:00AM -0400, Jean-François Dagenais wrote:
>> As discussed here: http://ez.analog.com/message/35852,
>> the 5587 revC and 5588 revB spec sheets contain a mistake
>> in the GPIO_DAT_STATx register description.
>>
>> According to R.Shnell at ADI, as well as my own
>> observations, it should read:
>> "GPIO data status (shows GPIO state when read for inputs)".
>>
>> This commit changes the get value function accordingly.
>>
>> A similar patch for gpio-adp5588 follows.
>>
>> Signed-off-by: Jean-François Dagenais <jeff.dagenais@gmail.com>
>> Acked-by: Michael Hennerich <michael.hennerich@analog.com>
>> ---
>> drivers/input/keyboard/adp5588-keys.c | 7 +++++++
>> 1 files changed, 7 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/input/keyboard/adp5588-keys.c b/drivers/input/keyboard/adp5588-keys.c
>> index 6412ced..b7a0f1a 100644
>> --- a/drivers/input/keyboard/adp5588-keys.c
>> +++ b/drivers/input/keyboard/adp5588-keys.c
>> @@ -78,6 +78,13 @@ static int adp5588_gpio_get_value(struct gpio_chip *chip, unsigned off)
>> unsigned int bank = ADP5588_BANK(kpad->gpiomap[off]);
>> unsigned int bit = ADP5588_BIT(kpad->gpiomap[off]);
>>
>> + mutex_lock(&kpad->gpio_lock);
>> + if (kpad->dir[bank] & bit) {
>> + int result = !!(kpad->dat_out[bank] & bit);
>> + mutex_unlock(&kpad->gpio_lock);
>> + return result;
>> + }
>> + mutex_unlock(&kpad->gpio_lock);
>> return !!(adp5588_read(kpad->client, GPIO_DAT_STAT1 + bank) & bit);
>
> This locking looks wrong as it is possible for adp5588_gpio_get_value()
> to get scheduled out after checking kpad->dir[bank] and releasing
> kpad->gpio_lock while another thread executes
> adp5588_gpio_direction_output() and modifies kpad->dir[bank].
>
> You should keep mutex for the entire duration; something like this:
>
> mutex_lock(&kpad->gpio_lock);
> if (kpad->dir[bank] & bit)
> val = kpad->dat_out[bank];
> else
> val = adp5588_read(kpad->client, GPIO_DAT_STAT1 + bank);
> mutex_unlock(&kpad->gpio_lock);
>
> return !!(val & bit);
>
Agreed, I think I wanted to minimize refactoring a bit too much and got distracted. I will send V2 shortly for both drivers.
> Thanks.
Thank you!
>
> --
> Dmitry

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