ACPI / processor: Introduce invalid_logical_cpuid()

In ACPI processor drivers, we use direct comparisons of cpu logical
id with -1 which are error prone in case logical cpuid is accidentally
assinged an error code and prevents us from returning an error-encoding
cpuid directly in some cases.

So introduce invalid_logical_cpuid() to identify cpu with invalid
logical cpu num, then it will be used to replace the direct comparisons
with -1.

Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpi_processor.c

@@ -275,7 +275,8 @@ static int acpi_processor_get_info(struct acpi_device *device)
 		 * Handle UP system running SMP kernel, with no CPU
 		 * entry in MADT
 		 */
-		if ((cpu_index == -1) && (num_online_cpus() == 1))
+		if (invalid_logical_cpuid(cpu_index)
+		    && (num_online_cpus() == 1))
 			cpu_index = 0;
 	}
 	pr->id = cpu_index;
@@ -285,7 +286,7 @@ static int acpi_processor_get_info(struct acpi_device *device)
 	 *  less than the max # of CPUs. They should be ignored _iff
 	 *  they are physically not present.
 	 */
-	if (pr->id == -1) {
+	if (invalid_logical_cpuid(pr->id)) {
 		int ret = acpi_processor_hotadd_init(pr);
 		if (ret)
 			return ret;

drivers/acpi/processor_pdc.c

@@ -52,10 +52,7 @@ static bool __init processor_physically_present(acpi_handle handle)
 	type = (acpi_type == ACPI_TYPE_DEVICE) ? 1 : 0;
 	cpuid = acpi_get_cpuid(handle, type, acpi_id);
 
-	if (cpuid == -1)
-		return false;
-
-	return true;
+	return !invalid_logical_cpuid(cpuid);
 }
 
 static void acpi_set_pdc_bits(u32 *buf)

include/linux/acpi.h

@@ -158,6 +158,11 @@ typedef u32 phys_cpuid_t;
 #define PHYS_CPUID_INVALID (phys_cpuid_t)(-1)
 #endif
 
+static inline bool invalid_logical_cpuid(u32 cpuid)
+{
+	return (int)cpuid < 0;
+}
+
 #ifdef CONFIG_ACPI_HOTPLUG_CPU
 /* Arch dependent functions for cpu hotplug support */
 int acpi_map_cpu(acpi_handle handle, phys_cpuid_t physid, int *pcpu);