Subject: Re: [PATCH v5 4/7] powerpc/powernv: detect supported nest pmus and its events

From: Daniel Axtens <[email-masked]>
Date: Wed, 22 Jul 2015 14:07:44 +1000

>  static struct perchip_nest_info p8_nest_perchip_info[P8_NEST_MAX_CHIPS];
> +static struct nest_pmu *per_nest_pmu_arr[P8_NEST_MAX_PMUS];
> +
> +static int nest_event_info(struct property *pp, char *name,
> +			struct nest_ima_events *p8_events, int string, u32 val)
'int string' is a bit confusing. 'bool is_string' might be clearer, but
I think it would be even better still to have different functions for
string and non-string cases, especially because you only need val in the
non-string case.

That will also allow you to give the functions clearer names. I think
the function is populating the event with info from the dt property (in
the string case) or the val argument (non-string case) - maybe the names
could reflect that somehow?
> +{
> +	char *buf;
> +

> +
> +static int nest_pmu_create(struct device_node *dev, int pmu_index)
> +{
> +	struct nest_ima_events **p8_events_arr, *p8_events;
> +	struct nest_pmu *pmu_ptr;
> +	struct property *pp;
> +	char *buf, *start;
> +	const __be32 *lval;
> +	u32 val;
> +	int idx = 0, ret;
> +
> +	if (!dev)
> +		return -EINVAL;
> +
> +	/* memory for nest pmus */
> +	pmu_ptr = kzalloc(sizeof(struct nest_pmu), GFP_KERNEL);
> +	if (!pmu_ptr)
> +		return -ENOMEM;
> +
> +	/* Needed for hotplug/migration */
> +	per_nest_pmu_arr[pmu_index] = pmu_ptr;
> +
> +	/* memory for nest pmu events */
> +	p8_events_arr = kzalloc((sizeof(struct nest_ima_events) * 64),
> +								GFP_KERNEL);
> +	if (!p8_events_arr)
> +		return -ENOMEM;
> +	p8_events = (struct nest_ima_events *)p8_events_arr;

I'm still quite uncomfortable with this.
 - Why * 64? Should it be * P8_NEST_MAX_EVENTS_SUPPORTED? Or is it a
different constant?
 - p8_events = p8_events_arr[0] would be clearer

> +
> +	/*
> +	 * Loop through each property
> +	 */
> +	for_each_property_of_node(dev, pp) {
> +		start = pp->name;
> +
> +		if (!strcmp(pp->name, "name")) {
> +			if (!pp->value ||
> +			   (strnlen(pp->value, pp->length) == pp->length) ||
> +			   (pp->length > P8_NEST_MAX_PMU_NAME_LEN))
> +				return -EINVAL;
> +
> +			buf = kzalloc(P8_NEST_MAX_PMU_NAME_LEN, GFP_KERNEL);
> +			if (!buf)
> +				return -ENOMEM;
> +
> +			/* Save the name to register it later */
> +			sprintf(buf, "Nest_%s", (char *)pp->value);
> +			pmu_ptr->pmu.name = (char *)buf;
> +			continue;
> +		}
> +
> +		/* Skip these, we dont need it */
"don't" instead of "dont".
> +		if (!strcmp(pp->name, "phandle") ||
> +		    !strcmp(pp->name, "device_type") ||
> +		    !strcmp(pp->name, "linux,phandle"))
> +			continue;
> +
> +		if (strncmp(pp->name, "unit.", 5) == 0) {
> +			/* Skip first few chars in the name */
The whole comment is pretty uninformative, as is the similar comment
below. If you need a comment at all, maybe something along the lines of
"Strip the prefix because <reason we don't need/want the prefix>"?
> +			start += 5;
> +			ret = nest_event_info(pp, start, p8_events++, 1, 0);
> +		} else if (strncmp(pp->name, "scale.", 6) == 0) {
> +			/* Skip first few chars in the name */
> +			start += 6;
> +			ret = nest_event_info(pp, start, p8_events++, 1, 0);
> +		} else {
> +			lval = of_get_property(dev, pp->name, NULL);
> +			val = (uint32_t)be32_to_cpup(lval);
> +
> +			ret = nest_event_info(pp, start, p8_events++, 0, val);
> +		}
> +
> +		if (ret)
> +			return ret;
> +
> +		/* book keeping */
> +		idx++;
You don't seem to use idx in this function, apart from incrementing it
here...?
> +	}
> +
> +	return 0;
> +}

-- 
Regards,
Daniel