linux-kernel - Re: [PATCH v2 04/23] counter: Provide a wrapper to access device private data

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Date:   Mon, 27 Dec 2021 12:02:14 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Cc:     William Breathitt Gray <vilhelm.gray@...il.com>,
        Lars-Peter Clausen <lars@...afoo.de>, kernel@...gutronix.de,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 04/23] counter: Provide a wrapper to access device
 private data

On Mon, Dec 27, 2021 at 10:45:07AM +0100, Uwe Kleine-König wrote:
> For now this just wraps accessing struct counter_device::priv. However
> this is about to change and converting drivers to this helper
> individually makes fixing device lifetime issues result in easier to
> review patches.
> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
> ---
>  drivers/counter/counter-core.c | 12 ++++++++++++
>  include/linux/counter.h        |  2 ++
>  2 files changed, 14 insertions(+)
> 
> diff --git a/drivers/counter/counter-core.c b/drivers/counter/counter-core.c
> index f053a43c6c04..00c41f28c101 100644
> --- a/drivers/counter/counter-core.c
> +++ b/drivers/counter/counter-core.c
> @@ -45,6 +45,18 @@ static struct bus_type counter_bus_type = {
>  
>  static dev_t counter_devt;
>  
> +/**
> + * counter_priv - access counter device private data
> + * @counter: counter device
> + *
> + * Get the counter device private data
> + */
> +void *counter_priv(const struct counter_device *const counter)
> +{
> +	return counter->priv;
> +}
> +EXPORT_SYMBOL_GPL(counter_priv);

Shouldn't this be usin gdev_get_drvdata() and using the private data
pointer that is already on the struct device structure itself?  The void
*priv; should be dropped from struct counter_device entirely.

Oh ick, I just now looked at 'struct counter_device', there are other
reference counting issues in there (hint, struct cdev has a reference
count...)  But that's independent of this patch series...

thanks,

greg k-h