linux-kernel - Re: [PATCH v1 6/9]powerpc/powernv: dt parser function for nest pmu and its events

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Date:	Wed, 03 Jun 2015 10:46:18 +1000
From:	Daniel Axtens <dja@...ens.net>
To:	Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	Stephane Eranian <eranian@...gle.com>,
	Paul Mackerras <paulus@...ba.org>,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	Anshuman Khandual <khandual@...ux.vnet.ibm.com>
Subject: Re: [PATCH v1 6/9]powerpc/powernv: dt parser function for nest pmu
 and its events


> +static int nest_pmu_create(struct device_node *dev, int pmu_index)
> +{
> +	struct ppc64_nest_ima_events **p8_events_arr;
> +	struct ppc64_nest_ima_events *p8_events;
> +	struct property *pp;
> +	char *buf;
> +	const __be32 *lval;
> +	u32 val;
> +	int len, idx = 0;
> +	struct nest_pmu *pmu_ptr;
> +	const char *start, *end;
> +
> +	if (!dev)
> +		return -EINVAL;
> +
> +	pmu_ptr = kzalloc(sizeof(struct nest_pmu), GFP_KERNEL);
> +	if (!pmu_ptr)
> +		return -ENOMEM;
> +
> +	/* Needed for hotplug/migration */
> +	per_nestpmu_arr[pmu_index] = pmu_ptr;
> +
> +	p8_events_arr = kzalloc((sizeof(struct ppc64_nest_ima_events) * 64),
> +								GFP_KERNEL);
> +	if (!p8_events_arr)
> +		return -ENOMEM;
> +	p8_events = (struct ppc64_nest_ima_events *)p8_events_arr;
I think you're trying to get the first element of the array here: why
not just `p8_events = p8_events_arr[0];`?

> +
> +	/*
> +	 * Loop through each property
> +	 */
> +	for_each_property_of_node(dev, pp) {
> +		start = pp->name;
> +		end = start + strlen(start);
> +		len = strlen(start);
> +
> +		if (!strcmp(pp->name, "name")) {
> +			if (!pp->value ||
> +			   (strnlen(pp->value, pp->length) >= pp->length))
> +				return -EINVAL;
> +
> +			buf = kzalloc(MAX_PMU_NAME_LEN, GFP_KERNEL);
> +			if (!buf)
> +				return -ENOMEM;
> +
> +			sprintf(buf, "Nest_%s", (char *)pp->value);
> +			pmu_ptr->pmu.name = (char *)buf;
> +			pmu_ptr->attr_groups[1] = &p8_nest_format_group;
> +			pmu_ptr->attr_groups[2] = &cpumask_nest_pmu_attr_group;
> +		}
> +
> +		/* Skip these, we dont need it */
> +		if (!strcmp(pp->name, "name") ||
> +		    !strcmp(pp->name, "phandle") ||
> +		    !strcmp(pp->name, "device_type") ||
> +		    !strcmp(pp->name, "linux,phandle"))
> +			continue;
> +
> +		buf = kzalloc(MAX_PMU_NAME_LEN, GFP_KERNEL);
> +		if (!buf)
> +			return -ENOMEM;
> +
> +		if (strncmp(pp->name, "unit.", 5) == 0) {
> +			start += 5;
> +			len = strlen(start);
> +			strncpy(buf, start, strlen(start));
You've just saved strlen(start), you could just use len. This also
applies in the next case below.
> +			p8_events->ev_name = buf;
> +
> +			if (!pp->value ||
> +                            (strnlen(pp->value, pp->length) >= pp->length))
> +				return -EINVAL;
The strnlen will never be greater than pp->length, so the only case this
will hit is if strnlen(pp->value, pp->length) == pp->length. This also
applies again below.

> +
> +			buf = kzalloc(MAX_PMU_NAME_LEN, GFP_KERNEL);
> +			if (!buf)
> +				return -ENOMEM;
> +
> +			strncpy(buf, (const char *)pp->value, pp->length);
> +			p8_events->ev_value = buf;
> +			idx++;
> +			p8_events++;
> +
> +		} else if (strncmp(pp->name, "scale.", 6) == 0) {
> +			start += 6;
> +			len = strlen(start);
> +			strncpy(buf, start, strlen(start));
> +			p8_events->ev_name = buf;
> +
> +			if (!pp->value ||
> +			   (strnlen(pp->value, pp->length) >= pp->length))
> +				return -EINVAL;
> +
> +			buf = kzalloc(MAX_PMU_NAME_LEN, GFP_KERNEL);
> +			if (!buf)
> +				return -ENOMEM;
> +
> +			strncpy(buf, (const char *)pp->value, pp->length);
> +			p8_events->ev_value = buf;
> +			idx++;
> +			p8_events++;
> +
> +		} else {
> +			strncpy(buf, start, len);
This is the only case where you actually use the orignal version of len.
This makes me think you could drop the variable entirely and just use
strlen(start) in all cases. I also don't see where `end` is used
anywhere in this function: could that be dropped?
> +			p8_events->ev_name = buf;
> +			lval = of_get_property(dev, pp->name, NULL);
> +			val = (uint32_t)be32_to_cpup(lval);
> +
> +			/*
> +			* Use DT property value as the event
> +			*/
I'm not sure if this is my mailer, but it looks like lines 2 and 3 of
that comment need to be indented to line up under the * in the first
line.
> +			buf = kzalloc(MAX_PMU_NAME_LEN, GFP_KERNEL);
> +			if (!buf)
> +                                return -ENOMEM;
> +
> +			sprintf(buf,"event=0x%x", val);
> +			p8_events->ev_value = buf;
> +			p8_events++;
> +			idx++;
> +		}
> +	}
> +
> +	return 0;
> +}
> +

> @@ -288,7 +427,7 @@ static int __init nest_pmu_init(void)
>  	cpumask_chip();
>  
>  	/*
> -	 * Detect the Nest PMU feature
> +	 * Detect the Nest PMU feature and register the pmus
>  	 */
>  	if (nest_ima_detect_parse())
>  		return 0;
As the changed comment indicates, this function changes the behaviour of
nest_ima_detect_parse. Given that it's a new function introduced by this
patch series, maybe it should also change names.



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