Re: [PATCH 5/9] perf: Add sysfs format attribute for pmu device

[Eric W. Biederman]

Jiri Olsa <jolsa@xxxxxxxxxx> writes:

> Adding 'format' attribute for pmu device that contains
> a syntax description on how to construct raw events.
>
> The event configuration is described in following
> struct pefr_event_attr attributes:
>
>   config
>   config1
>   config2
>
> Each line of the format file describes mapping of name
> and bitfield definition within one of abve attributes.
>
> eg:
>   event   config:0-7
>   umask   config:8-15
>   usr     config:16
>   os      config:17
>   edge    config:18
>   any     config:21
>   inv     config:23
>   cmask   config:24-31
>
> Line syntax:
>   line:      NAME config ':' bits
>   config:    'config' | 'config1' | 'config2"
>   bits:      bits ',' bit_term | bit_term
>   bit_term:  VALUE '-' VALUE | VALUE
>
> Adding event_format callback to the struct pmu, which provides
> the format information. The pmu shall override this function
> and provide its own specific format information.
>
> If not overloaded the default format information is used:
>
>   config  config:0-63
>   config1 config1:0-63
>   config2 config2:0-63
>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>

> @@ -5492,8 +5492,31 @@ type_show(struct device *dev, struct device_attribute *attr, char *page)
>  	return snprintf(page, PAGE_SIZE-1, "%d\n", pmu->type);
>  }
>  
> +static ssize_t perf_default_event_format(struct pmu *pmu, char *page)
> +{
> +	ssize_t ret;
> +
> +	ret  = sprintf(page,       "config  config:0-63\n");
> +	ret += sprintf(page + ret, "config1 config1:0-63\n");
> +	ret += sprintf(page + ret, "config2 config2:0-63\n");

This looks like abuse of sysfs.  The rule is one value per file.
When you start adding newlines I can't see how this format attribute can
be considered one value.

Eric
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