linux-kernel - Re: [PATCH v1 2/4] coresight: add and remove panic callback for sink

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Date:   Mon, 5 Jun 2017 10:24:41 +0100
From:   Suzuki K Poulose <Suzuki.Poulose@....com>
To:     Leo Yan <leo.yan@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Will Deacon <will.deacon@....com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Mike Leach <mike.leach@...aro.org>,
        Chunyan Zhang <zhang.chunyan@...aro.org>
Subject: Re: [PATCH v1 2/4] coresight: add and remove panic callback for sink

On 03/06/17 15:42, Leo Yan wrote:
> If the sink device has panic callback function, add the panic callback
> node for coresight panic dump list when the sink device is enabled;
> also cleanup the node when the sink device is disabled.
>
> Signed-off-by: Leo Yan <leo.yan@...aro.org>
> ---
>  drivers/hwtracing/coresight/coresight.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
> index 0c37356..5928886 100644
> --- a/drivers/hwtracing/coresight/coresight.c
> +++ b/drivers/hwtracing/coresight/coresight.c
> @@ -138,6 +138,13 @@ static int coresight_enable_sink(struct coresight_device *csdev, u32 mode)
>  			if (ret)
>  				return ret;
>  		}
> +
> +		/* Add kernel panic callback */
> +		if (sink_ops(csdev)->panic_cb) {
> +			ret = coresight_add_panic_cb(csdev);
> +			if (ret)
> +				return ret;
> +		}
>  		csdev->enable = true;
>  	}
>
> @@ -149,6 +156,10 @@ static int coresight_enable_sink(struct coresight_device *csdev, u32 mode)
>  static void coresight_disable_sink(struct coresight_device *csdev)
>  {
>  	if (atomic_dec_return(csdev->refcnt) == 0) {
> +		/* Remove kernel panic callback */
> +		if (sink_ops(csdev)->panic_cb)
> +			coresight_del_panic_cb(csdev);
> +
>  		if (sink_ops(csdev)->disable) {
>  			sink_ops(csdev)->disable(csdev);
>  			csdev->enable = false;
>

Just a thought, instead of adding/deleting every time the sink is enabled,
could we add/del the device once for-ever and let the panic_cb decide to dump
it based on whether the device was active or not ?

Suzuki