linux-kernel - Re: [PATCH v3] iio: adc: stmpe-adc: Fix wait_for_completion

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Date:   Tue, 12 Apr 2022 08:52:13 +0000
From:   Philippe Schenker <philippe.schenker@...adex.com>
To:     "alexandre.torgue@...s.st.com" <alexandre.torgue@...s.st.com>,
        "linmq006@...il.com" <linmq006@...il.com>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] iio: adc: stmpe-adc: Fix wait_for_completion_timeout
 return value check

On Tue, 2022-04-12 at 06:51 +0000, Miaoqian Lin wrote:
> wait_for_completion_timeout() returns unsigned long not long.
> it returns 0 if timed out, and positive if completed.
> The check for <= 0 is ambiguous and should be == 0 here
> indicating timeout which is the only error case
> 
> Fixes: e813dde6f833 ("iio: stmpe-adc: Use
> wait_for_completion_timeout")
> Signed-off-by: Miaoqian Lin <linmq006@...il.com>

Reviewed-by: Philippe Schenker <philippe.schenker@...adex.com>

> ---
> changes in v2:
> - Fix same issue in stmpe_read_temp.
> ---
> changes in v3:
> - update the patch subject.
> ---
>  drivers/iio/adc/stmpe-adc.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/adc/stmpe-adc.c b/drivers/iio/adc/stmpe-adc.c
> index d2d405388499..83e0ac4467ca 100644
> --- a/drivers/iio/adc/stmpe-adc.c
> +++ b/drivers/iio/adc/stmpe-adc.c
> @@ -61,7 +61,7 @@ struct stmpe_adc {
>  static int stmpe_read_voltage(struct stmpe_adc *info,
>                 struct iio_chan_spec const *chan, int *val)
>  {
> -       long ret;
> +       unsigned long ret;
>  
>         mutex_lock(&info->lock);
>  
> @@ -79,7 +79,7 @@ static int stmpe_read_voltage(struct stmpe_adc
> *info,
>  
>         ret = wait_for_completion_timeout(&info->completion,
> STMPE_ADC_TIMEOUT);
>  
> -       if (ret <= 0) {
> +       if (ret == 0) {
>                 stmpe_reg_write(info->stmpe, STMPE_REG_ADC_INT_STA,
>                                 STMPE_ADC_CH(info->channel));
>                 mutex_unlock(&info->lock);
> @@ -96,7 +96,7 @@ static int stmpe_read_voltage(struct stmpe_adc
> *info,
>  static int stmpe_read_temp(struct stmpe_adc *info,
>                 struct iio_chan_spec const *chan, int *val)
>  {
> -       long ret;
> +       unsigned long ret;
>  
>         mutex_lock(&info->lock);
>  
> @@ -114,7 +114,7 @@ static int stmpe_read_temp(struct stmpe_adc *info,
>  
>         ret = wait_for_completion_timeout(&info->completion,
> STMPE_ADC_TIMEOUT);
>  
> -       if (ret <= 0) {
> +       if (ret == 0) {
>                 mutex_unlock(&info->lock);
>                 return -ETIMEDOUT;
>         }