[PATCH 2/2] e_powersaver: Require setting a module parameter to enable it

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The Kconfig text and comment at the top of the file say this is
DANGEROUS.  According to Rafał Bilski it is not so bad as it used to
be, but he still didn't think it should be auto-loaded.

Rafał already made a similar change to longhaul.

References: http://www.spinics.net/lists/cpufreq/msg02919.html
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
 drivers/cpufreq/e_powersaver.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/cpufreq/e_powersaver.c b/drivers/cpufreq/e_powersaver.c
index a0d2a42..880be39 100644
--- a/drivers/cpufreq/e_powersaver.c
+++ b/drivers/cpufreq/e_powersaver.c
@@ -45,6 +45,7 @@ static struct eps_cpu_data *eps_cpu[NR_CPUS];
 static int freq_failsafe_off;
 static int voltage_failsafe_off;
 static int set_max_voltage;
+static int enable;
 static int ignore_acpi_limit;
@@ -410,6 +411,10 @@ static int __init eps_init(void)
 	if (!x86_match_cpu(eps_cpu_id) || boot_cpu_data.x86_model < 10)
 		return -ENODEV;
+	if (!enable) {
+		printk(KERN_ERR "eps: Option \"enable\" not set. Aborting.\n");
+		return -ENODEV;
+	}
 	if (cpufreq_register_driver(&eps_driver))
 		return -EINVAL;
 	return 0;
@@ -432,6 +437,10 @@ MODULE_PARM_DESC(ignore_acpi_limit, "Don't check ACPI's processor speed limit");
 module_param(set_max_voltage, int, 0644);
 MODULE_PARM_DESC(set_max_voltage, "Set maximum CPU voltage (mV) C7-M only");
+/* By default driver is disabled to prevent incompatible
+ * system freeze. */
+module_param(enable, int, 0644);
+MODULE_PARM_DESC(enable, "Enable driver");
 MODULE_AUTHOR("Rafal Bilski <rafalbilski@xxxxxxxxxx>");
 MODULE_DESCRIPTION("Enhanced PowerSaver driver for VIA C7 CPU's.");

Ben Hutchings
One of the nice things about standards is that there are so many of them.

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