linux-kernel - Re: [PATCH 5/6] perf/core: Use ioctl to communicate driver configuration to kernel

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Message-ID: <20180703134026.GA3728@krava>
Date:   Tue, 3 Jul 2018 15:40:26 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     peterz@...radead.org, acme@...nel.org, mingo@...hat.com,
        tglx@...utronix.de, alexander.shishkin@...ux.intel.com,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        will.deacon@....com, mark.rutland@....com, namhyung@...nel.org,
        adrian.hunter@...el.com, ast@...nel.org,
        gregkh@...uxfoundation.org, hpa@...or.com,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 5/6] perf/core: Use ioctl to communicate driver
 configuration to kernel

On Mon, Jul 02, 2018 at 04:33:29PM -0600, Mathieu Poirier wrote:

SNIP

> +static int
> +perf_event_process_drv_config(struct perf_event *event, char *config_str)
> +{
> +	int ret = -EINVAL;
> +	void *drv_data;
> +
> +	/* Make sure ctx.mutex it held */
> +	lockdep_assert_held(&event->ctx->mutex);
> +
> +	/* Children take their configuration from their parent */
> +	if (WARN_ON_ONCE(event->parent))
> +		goto out;
> +
> +	drv_data = event->pmu->drv_config_validate(event, config_str);
> +	if (!drv_data)
> +		goto out;

what's this check for? doc does not mention that,
also the coresight callback does not return NULL

jirka