linux-kernel - Re: [PATCH v3 5/7] iio: adc: exynos: Use input_device

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Date:   Fri, 5 Jun 2020 21:49:48 +0200
From:   Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:     Andrzej Pietrasiewicz <andrzej.p@...labora.com>
Cc:     linux-pm@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-input@...r.kernel.org,
        linux-tegra@...r.kernel.org, patches@...nsource.cirrus.com,
        ibm-acpi-devel@...ts.sourceforge.net,
        platform-driver-x86@...r.kernel.org,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Vladimir Zapolskiy <vz@...ia.com>,
        Sylvain Lemieux <slemieux.tyco@...il.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Barry Song <baohua@...nel.org>,
        Michael Hennerich <michael.hennerich@...log.com>,
        Nick Dyer <nick@...anahar.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Ferruh Yigit <fery@...ress.com>,
        Sangwon Jee <jeesw@...fas.com>,
        Peter Hutterer <peter.hutterer@...hat.com>,
        Henrique de Moraes Holschuh <ibm-acpi@....eng.br>,
        kernel@...labora.com
Subject: Re: [PATCH v3 5/7] iio: adc: exynos: Use input_device_enabled()

On Fri, Jun 05, 2020 at 07:33:33PM +0200, Andrzej Pietrasiewicz wrote:
> A new helper is available, so use it. Inspecting 'users' member of
> input_dev requires taking device's mutex.
> 
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@...labora.com>
> ---
>  drivers/iio/adc/exynos_adc.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/adc/exynos_adc.c b/drivers/iio/adc/exynos_adc.c
> index 22131a677445..294715bafe25 100644
> --- a/drivers/iio/adc/exynos_adc.c
> +++ b/drivers/iio/adc/exynos_adc.c
> @@ -630,10 +630,13 @@ static irqreturn_t exynos_ts_isr(int irq, void *dev_id)
>  	struct exynos_adc *info = dev_id;
>  	struct iio_dev *dev = dev_get_drvdata(info->dev);
>  	u32 x, y;
> -	bool pressed;
> +	bool pressed, cont;
>  	int ret;
>  
> -	while (info->input->users) {
> +	mutex_lock(&info->input->mutex);
> +	cont = input_device_enabled(info->input);
> +	mutex_unlock(&info->input->mutex);
> +	while (cont) {
>  		ret = exynos_read_s3c64xx_ts(dev, &x, &y);
>  		if (ret == -ETIMEDOUT)
>  			break;
> @@ -651,6 +654,10 @@ static irqreturn_t exynos_ts_isr(int irq, void *dev_id)
>  		input_sync(info->input);
>  
>  		usleep_range(1000, 1100);
> +
> +		mutex_lock(&info->input->mutex);
> +		cont = input_device_enabled(info->input);
> +		mutex_unlock(&info->input->mutex);
>  	}

The mutex doesn't really protect anything here, but I would nevertheless
suggest this sequence instead:

lock()
while (test) {
	unlock()
	...
	lock()
}
unlock()

Best Regards,
Michał Mirosław