cpufreq: Add new helper cpufreq_table_validate_and_show()

Almost every cpufreq driver is required to validate its frequency table with:
cpufreq_frequency_table_cpuinfo() and then expose it to cpufreq core with:
cpufreq_frequency_table_get_attr().

This patch creates another helper routine cpufreq_table_validate_and_show() that
will do both these steps in a single call and will return 0 for success, error
otherwise.

This also fixes potential bugs in cpufreq drivers where people have called
cpufreq_frequency_table_get_attr() before calling
cpufreq_frequency_table_cpuinfo(), as the later may fail.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/freq_table.c

@@ -219,6 +219,18 @@ void cpufreq_frequency_table_put_attr(unsigned int cpu)
 }
 EXPORT_SYMBOL_GPL(cpufreq_frequency_table_put_attr);
 
+int cpufreq_table_validate_and_show(struct cpufreq_policy *policy,
+				      struct cpufreq_frequency_table *table)
+{
+	int ret = cpufreq_frequency_table_cpuinfo(policy, table);
+
+	if (!ret)
+		cpufreq_frequency_table_get_attr(table, policy->cpu);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(cpufreq_table_validate_and_show);
+
 void cpufreq_frequency_table_update_policy_cpu(struct cpufreq_policy *policy)
 {
 	pr_debug("Updating show_table for new_cpu %u from last_cpu %u\n",

include/linux/cpufreq.h

@@ -410,5 +410,7 @@ extern struct freq_attr cpufreq_freq_attr_scaling_available_freqs;
 void cpufreq_frequency_table_get_attr(struct cpufreq_frequency_table *table,
 				      unsigned int cpu);
 void cpufreq_frequency_table_put_attr(unsigned int cpu);
+int cpufreq_table_validate_and_show(struct cpufreq_policy *policy,
+				      struct cpufreq_frequency_table *table);
 
 #endif /* _LINUX_CPUFREQ_H */