linux-kernel - Re: [PATCH v3] iio: trigger: warn about non-registered iio trigger getting attempt

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Date:   Thu, 16 Jun 2022 13:59:45 +0000
From:   Dmitry Rokosov <DDRokosov@...rdevices.ru>
To:     "andy.shevchenko@...il.com" <andy.shevchenko@...il.com>
CC:     "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "noname.nuno@...il.com" <noname.nuno@...il.com>,
        kernel <kernel@...rdevices.ru>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rockosov@...il.com" <rockosov@...il.com>
Subject: Re: [PATCH v3] iio: trigger: warn about non-registered iio trigger
 getting attempt

Hello Andy,

Could you please review this patch version if possible?
I've changed WARN() to WARN_ONCE() and fixed commit msg as you suggested
in the v2.

On Tue, Jun 07, 2022 at 06:39:18PM +0000, Dmitry Rokosov wrote:
> As a part of patch series about wrong trigger register() and get()
> calls order in the some IIO drivers trigger initialization path:
> 
> https://lore.kernel.org/all/20220524181150.9240-1-ddrokosov@sberdevices.ru/
> 
> runtime WARN_ONCE() is added to alarm IIO driver authors who make such
> a mistake.
> 
> When an IIO driver allocates a new IIO trigger, it should register it
> before calling the get() operation. In other words, each IIO driver
> must abide by IIO trigger alloc()/register()/get() calls order.
> 
> Signed-off-by: Dmitry Rokosov <ddrokosov@...rdevices.ru>
> ---
> Changes:
> v1 -> v2: totally reworked the patch, used trig->list entry instead of
>           trig->owner as driver registration indicator.
>           It works perfectly for both builtin and built as a module
>           drivers.
> 
> v2 -> v3: changed WARN() call to WARN_ONCE() to avoid warn spamming
>           during deferred probe() as Andy suggested.
> ---
>  drivers/iio/industrialio-trigger.c | 2 ++
>  include/linux/iio/trigger.h        | 5 +++++
>  2 files changed, 7 insertions(+)
> 
> diff --git a/drivers/iio/industrialio-trigger.c b/drivers/iio/industrialio-trigger.c
> index f504ed351b3e..d6277e72d515 100644
> --- a/drivers/iio/industrialio-trigger.c
> +++ b/drivers/iio/industrialio-trigger.c
> @@ -581,6 +581,8 @@ struct iio_trigger *viio_trigger_alloc(struct device *parent,
>  	if (trig->name == NULL)
>  		goto free_descs;
>  
> +	INIT_LIST_HEAD(&trig->list);
> +
>  	trig->subirq_chip.name = trig->name;
>  	trig->subirq_chip.irq_mask = &iio_trig_subirqmask;
>  	trig->subirq_chip.irq_unmask = &iio_trig_subirqunmask;
> diff --git a/include/linux/iio/trigger.h b/include/linux/iio/trigger.h
> index 4c69b144677b..03b1d6863436 100644
> --- a/include/linux/iio/trigger.h
> +++ b/include/linux/iio/trigger.h
> @@ -93,6 +93,11 @@ static inline void iio_trigger_put(struct iio_trigger *trig)
>  static inline struct iio_trigger *iio_trigger_get(struct iio_trigger *trig)
>  {
>  	get_device(&trig->dev);
> +
> +	WARN_ONCE(list_empty(&trig->list),
> +		  "Getting non-registered iio trigger %s is prohibited\n",
> +		  trig->name);
> +
>  	__module_get(trig->owner);
>  
>  	return trig;
> -- 
> 2.36.0

-- 
Thank you,
Dmitry