ACPI: Export FADT pm_profile integer value to userspace

There are a lot userspace approaches to detect the usage of the
platform (laptop, workstation, server, ...) and adjust kernel tunables
accordingly (io/process scheduler, power management, ...).

These approaches need constant maintaining and are ugly to implement
(detect PCMCIA controller -> laptop,
does not work on recent systems anymore, ...)
On ACPI systems there is an easy and reliable way (if implemented
in BIOS and most recent platforms have this value set).
-> export it to userspace.

Signed-off-by: Thomas Renninger <trenn@suse.de>
Acked-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>

2 files changed, 35 insertions, 1 deletions

diff --git a/Documentation/ABI/stable/sysfs-acpi-pmprofile b/Documentation/ABI/stable/sysfs-acpi-pmprofile
new file mode 100644
index 000000000000..964c7a8afb26
--- /dev/null
+++ b/Documentation/ABI/stable/sysfs-acpi-pmprofile
@@ -0,0 +1,22 @@
+What:           /sys/firmware/acpi/pm_profile
+Date:           03-Nov-2011
+KernelVersion:  v3.2
+Contact:        linux-acpi@vger.kernel.org
+Description:    The ACPI pm_profile sysfs interface exports the platform
+                power management (and performance) requirement expectations
+                as provided by BIOS. The integer value is directly passed as
+                retrieved from the FADT ACPI table.
+Values:         For possible values see ACPI specification:
+                5.2.9 Fixed ACPI Description Table (FADT)
+                Field: Preferred_PM_Profile
+
+                Currently these values are defined by spec:
+                0 Unspecified
+                1 Desktop
+                2 Mobile
+                3 Workstation
+                4 Enterprise Server
+                5 SOHO Server
+                6 Appliance PC
+                7 Performance Server
+                >7 Reserved
diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
index c538d0ef10ff..9f66181c814e 100644
--- a/drivers/acpi/sysfs.c
+++ b/drivers/acpi/sysfs.c
@@ -706,11 +706,23 @@ static void __exit interrupt_stats_exit(void)
         return;
 }
 
+static ssize_t
+acpi_show_profile(struct device *dev, struct device_attribute *attr,
+                  char *buf)
+{
+        return sprintf(buf, "%d\n", acpi_gbl_FADT.preferred_profile);
+}
+
+static const struct device_attribute pm_profile_attr =
+        __ATTR(pm_profile, S_IRUGO, acpi_show_profile, NULL);
+
 int __init acpi_sysfs_init(void)
 {
         int result;
 
         result = acpi_tables_sysfs_init();
-
+        if (result)
+                return result;
+        result = sysfs_create_file(acpi_kobj, &pm_profile_attr.attr);
         return result;
 }