linux-kernel - Re: [PATCH v1] counter: interrupt-cnt: add counter_push

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Date:   Wed, 24 Nov 2021 15:09:05 +0900
From:   William Breathitt Gray <vilhelm.gray@...il.com>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        David Jander <david@...tonic.nl>,
        Robin van der Gracht <robin@...tonic.nl>,
        linux-iio@...r.kernel.org, Jonathan Cameron <jic23@...nel.org>
Subject: Re: [PATCH v1] counter: interrupt-cnt: add counter_push_event()

On Tue, Nov 23, 2021 at 02:45:40PM +0100, Oleksij Rempel wrote:
> Add counter_push_event() to notify user space about new pulses
> 
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> ---
>  drivers/counter/interrupt-cnt.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/counter/interrupt-cnt.c b/drivers/counter/interrupt-cnt.c
> index 8514a87fcbee..b237137b552b 100644
> --- a/drivers/counter/interrupt-cnt.c
> +++ b/drivers/counter/interrupt-cnt.c
> @@ -31,6 +31,8 @@ static irqreturn_t interrupt_cnt_isr(int irq, void *dev_id)
>  
>  	atomic_inc(&priv->count);
>  
> +	counter_push_event(&priv->counter, COUNTER_EVENT_OVERFLOW, 0);
> +
>  	return IRQ_HANDLED;
>  }
>  
> -- 
> 2.30.2

Hi Oleksij,

It looks like this is pushing a COUNTER_EVENT_OVERFLOW event every time
an interrupt is handled, which I suspect is not what you want to happen.
The COUNTER_EVENT_OVERFLOW event indicates a count value overflow event,
so you'll need to check for a count value overflow before pushing the
event.

It would be good idea to implement a ceiling extension as well (you can
use the COUNTER_COMP_CEILING() macro) so that users can configure the
particular point where the value overflows.

William Breathitt Gray

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