linux-kernel - Re: [PATCH v3 02/13] iio: adc: ad7091r: Populate device driver data field

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Date:   Thu, 7 Dec 2023 17:18:09 -0600
From:   David Lechner <dlechner@...libre.com>
To:     Marcelo Schmitt <marcelo.schmitt@...log.com>
Cc:     apw@...onical.com, joe@...ches.com, dwaipayanray1@...il.com,
        lukas.bulwahn@...il.com, paul.cercueil@...log.com,
        Michael.Hennerich@...log.com, lars@...afoo.de, jic23@...nel.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, dan.carpenter@...aro.org,
        marcelo.schmitt1@...il.com, linux-iio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 02/13] iio: adc: ad7091r: Populate device driver data field

On Thu, Dec 7, 2023 at 12:38 PM Marcelo Schmitt
<marcelo.schmitt@...log.com> wrote:
>
> Set device driver data so it can be retrieved when handling alert
> events, avoiding null pointer dereference.
>
> Fixes: ca69300173b6 ("iio: adc: Add support for AD7091R5 ADC")
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
> ---
>  drivers/iio/adc/ad7091r-base.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/iio/adc/ad7091r-base.c b/drivers/iio/adc/ad7091r-base.c
> index 8e252cde735b..0f192fbecbd4 100644
> --- a/drivers/iio/adc/ad7091r-base.c
> +++ b/drivers/iio/adc/ad7091r-base.c
> @@ -232,6 +232,7 @@ int ad7091r_probe(struct device *dev, const char *name,
>         iio_dev->channels = chip_info->channels;
>
>         if (irq) {
> +               dev_set_drvdata(st->dev, iio_dev);
>                 ret = devm_request_threaded_irq(dev, irq, NULL,
>                                 ad7091r_event_handler,
>                                 IRQF_TRIGGER_FALLING | IRQF_ONESHOT, name, st);
> --
> 2.42.0
>
>

Instead of introducing a new relationship between iio_dev and st, why
not pass iio_dev to devm_request_threaded_irq() instead of st and then
use iio_priv() to get st in ad7091r_event_handler?

diff --git a/drivers/iio/adc/ad7091r-base.c b/drivers/iio/adc/ad7091r-base.c
index 8e252cde735b..0e5d3d2e9c98 100644
--- a/drivers/iio/adc/ad7091r-base.c
+++ b/drivers/iio/adc/ad7091r-base.c
@@ -174,8 +174,8 @@ static const struct iio_info ad7091r_info = {

 static irqreturn_t ad7091r_event_handler(int irq, void *private)
 {
-    struct ad7091r_state *st = (struct ad7091r_state *) private;
-    struct iio_dev *iio_dev = dev_get_drvdata(st->dev);
+    struct iio_dev *iio_dev = private;
+    struct ad7091r_state *st = iio_priv(iio_dev);
     unsigned int i, read_val;
     int ret;
     s64 timestamp = iio_get_time_ns(iio_dev);
@@ -234,7 +234,7 @@ int ad7091r_probe(struct device *dev, const char *name,
     if (irq) {
         ret = devm_request_threaded_irq(dev, irq, NULL,
                 ad7091r_event_handler,
-                IRQF_TRIGGER_FALLING | IRQF_ONESHOT, name, st);
+                IRQF_TRIGGER_FALLING | IRQF_ONESHOT, name, iio_dev);
         if (ret)
             return ret;
     }