ACPI: thinkpad-acpi: improve thinkpad detection

Improve the detection of ThinkPads, so as to reduce the chances of false
positives.

Since this could potentially add false negatives on the very old models,
add a module parameter to force the detection of a thinkpad.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>

3 files changed, 21 insertions, 0 deletions

diff --git a/Documentation/thinkpad-acpi.txt b/Documentation/thinkpad-acpi.txt
index 20d5ec309cbd..1a42b77e2ece 100644
--- a/Documentation/thinkpad-acpi.txt
+++ b/Documentation/thinkpad-acpi.txt
@@ -716,3 +716,10 @@ to enable more than one output class, just add their values.
 
 There is also a kernel build option to enable more debugging
 information, which may be necessary to debug driver problems.
+
+Force loading of module
+-----------------------
+
+If thinkpad-acpi refuses to detect your ThinkPad, you can try to specify
+the module parameter force_load=1.  Regardless of whether this works or
+not, please contact ibm-acpi-devel@lists.sourceforge.net with a report.
diff --git a/drivers/misc/thinkpad_acpi.c b/drivers/misc/thinkpad_acpi.c
index 56112684967b..cddf81bb2d97 100644
--- a/drivers/misc/thinkpad_acpi.c
+++ b/drivers/misc/thinkpad_acpi.c
@@ -2881,6 +2881,16 @@ static int __init probe_for_thinkpad(void)
                 return -ENODEV;
         }
 
+        /*
+         * Risks a regression on very old machines, but reduces potential
+         * false positives a damn great deal
+         */
+        if (!is_thinkpad)
+                is_thinkpad = dmi_name_in_vendors("IBM");
+
+        if (!is_thinkpad && !force_load)
+                return -ENODEV;
+
         return 0;
 }
 
@@ -2986,6 +2996,9 @@ module_param(experimental, int, 0);
 static u32 dbg_level;
 module_param_named(debug, dbg_level, uint, 0);
 
+static int force_load;
+module_param(force_load, int, 0);
+
 #define IBM_PARAM(feature) \
         module_param_call(feature, set_ibm_param, NULL, NULL, 0)
 
diff --git a/drivers/misc/thinkpad_acpi.h b/drivers/misc/thinkpad_acpi.h
index 97467b71b727..20203981cb7a 100644
--- a/drivers/misc/thinkpad_acpi.h
+++ b/drivers/misc/thinkpad_acpi.h
@@ -128,6 +128,7 @@ static char *next_cmd(char **cmds);
 /* Module */
 static int experimental;
 static u32 dbg_level;
+static int force_load;
 static char *ibm_thinkpad_ec_found;
 
 static char* check_dmi_for_ec(void);