ACPI: Add "acpi_no_initrd_override" kernel parameter

The acpi_no_initrd_override parameter permits to disable the load of an ACPI
table from the initramfs.

Signed-off-by: Eric Piel <eric.piel@tremplin-utc.net>
Signed-off-by: Len Brown <len.brown@intel.com>

2 files changed, 18 insertions, 1 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 8fd5aa40585..ef2316a1a73 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -175,6 +175,9 @@ and is between 256 and 4096 characters. It is defined in the file
 
         acpi_no_auto_ssdt       [HW,ACPI] Disable automatic loading of SSDT
 
+        acpi_no_initrd_override [KNL,ACPI]
+                        Disable loading custom ACPI tables from the initramfs
+
         acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
                         Format: To spoof as Windows 98: ="Microsoft Windows"
 
diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index bbd8360bfb2..2b41bdddbeb 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -77,6 +77,10 @@ static struct workqueue_struct *kacpi_notify_wq;
 #define OSI_STRING_LENGTH_MAX 64        /* arbitrary */
 static char osi_additional_string[OSI_STRING_LENGTH_MAX];
 
+#ifdef CONFIG_ACPI_CUSTOM_DSDT_INITRD
+static int acpi_no_initrd_override;
+#endif
+
 /*
  * "Ode to _OSI(Linux)"
  *
@@ -386,7 +390,8 @@ acpi_os_table_override(struct acpi_table_header * existing_table,
                 *new_table = (struct acpi_table_header *)AmlCode;
 #endif
 #ifdef CONFIG_ACPI_CUSTOM_DSDT_INITRD
-        if (strncmp(existing_table->signature, "DSDT", 4) == 0) {
+        if ((strncmp(existing_table->signature, "DSDT", 4) == 0) &&
+            !acpi_no_initrd_override) {
                 struct acpi_table_header *initrd_table = acpi_find_dsdt_initrd();
                 if (initrd_table)
                         *new_table = initrd_table;
@@ -402,6 +407,15 @@ acpi_os_table_override(struct acpi_table_header * existing_table,
         return AE_OK;
 }
 
+#ifdef CONFIG_ACPI_CUSTOM_DSDT_INITRD
+int __init acpi_no_initrd_override_setup(char *s)
+{
+        acpi_no_initrd_override = 1;
+        return 1;
+}
+__setup("acpi_no_initrd_override", acpi_no_initrd_override_setup);
+#endif
+
 static irqreturn_t acpi_irq(int irq, void *dev_id)
 {
         return (*acpi_irq_handler) (acpi_irq_context) ? IRQ_HANDLED : IRQ_NONE;