linux-kernel - Re: [PATCH v2 2/5] perf: Allow a PMU to have a parent.

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Message-ID: <f8123e7c-36a6-a302-1101-e778622dc997@linux.intel.com>
Date:   Mon, 27 Mar 2023 13:04:08 -0400
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        linux-cxl@...r.kernel.org, peterz@...radead.org
Cc:     mingo@...hat.com, acme@...nel.org, mark.rutland@....com,
        will@...nel.org, dan.j.williams@...el.com, linuxarm@...wei.com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Davidlohr Bueso <dave@...olabs.net>,
        Dave Jiang <dave.jiang@...el.com>
Subject: Re: [PATCH v2 2/5] perf: Allow a PMU to have a parent.



On 2023-03-24 1:13 p.m., Jonathan Cameron wrote:
> Some PMUs have well defined parents such as PCI devices.
> As the device_initialize() and device_add() are all within
> pmu_dev_alloc() which is called from perf_pmu_register()
> there is no opportunity to set the parent from within a driver.
> 
> Add a struct device *parent field to struct pmu and use that
> to set the parent.

Why we want a PMU parent? Maybe I missed it. I don't see that the parent
is used anywhere.

Thanks,
Kan

> 
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> ---
>  include/linux/perf_event.h | 1 +
>  kernel/events/core.c       | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
> index d5628a7b5eaa..b99db1eda72c 100644
> --- a/include/linux/perf_event.h
> +++ b/include/linux/perf_event.h
> @@ -303,6 +303,7 @@ struct pmu {
>  
>  	struct module			*module;
>  	struct device			*dev;
> +	struct device			*parent;
>  	const struct attribute_group	**attr_groups;
>  	const struct attribute_group	**attr_update;
>  	const char			*name;
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index fb3e436bcd4a..a84c282221f2 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -11367,6 +11367,7 @@ static int pmu_dev_alloc(struct pmu *pmu)
>  
>  	dev_set_drvdata(pmu->dev, pmu);
>  	pmu->dev->bus = &pmu_bus;
> +	pmu->dev->parent = pmu->parent;
>  	pmu->dev->release = pmu_dev_release;
>  
>  	ret = dev_set_name(pmu->dev, "%s", pmu->name);