ACPI: make _OSI(Linux) console messages smarter

If BIOS invokes _OSI(Linux), the kernel response
depends on what the ACPI DMI list knows about the system,
and that is reflectd in dmesg:

1) System unknown to DMI:

ACPI: BIOS _OSI(Linux) query ignored
ACPI: DMI System Vendor: LENOVO
ACPI: DMI Product Name: 7661W1P
ACPI: DMI Product Version: ThinkPad T61
ACPI: DMI Board Name: 7661W1P
ACPI: DMI BIOS Vendor: LENOVO
ACPI: DMI BIOS Date: 10/18/2007
ACPI: Please send DMI info above to linux-acpi@vger.kernel.org
ACPI: If "acpi_osi=Linux" works better, please notify linux-acpi@vger.kernel.org

2) System known to DMI, but effect of OSI(Linux) unknown:

ACPI: DMI detected: Lenovo ThinkPad T61
...
ACPI: BIOS _OSI(Linux) query ignored via DMI
ACPI: If "acpi_osi=Linux" works better, please notify linux-acpi@vger.kernel.org

3) System known to DMI, which disables _OSI(Linux):

ACPI: DMI detected: Lenovo ThinkPad T61
...
ACPI: BIOS _OSI(Linux) query ignored via DMI

4) System known to DMI, which enable _OSI(Linux):

ACPI: DMI detected: Lenovo ThinkPad T61
ACPI: Added _OSI(Linux)
...
ACPI: BIOS _OSI(Linux) query honored via DMI

cmdline overrides take precidence over the built-in
default and the DMI prescribed default.
cmdline "acpi_osi=Linux" results in:

ACPI: BIOS _OSI(Linux) query honored via cmdline

Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 102 insertions, 20 deletions

diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
index 15f095ea795e..e53fb516f9d4 100644
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -77,7 +77,55 @@ static struct workqueue_struct *kacpi_notify_wq;
 #define OSI_STRING_LENGTH_MAX 64        /* arbitrary */
 static char osi_additional_string[OSI_STRING_LENGTH_MAX];
 
-static int osi_linux;           /* disable _OSI(Linux) by default */
+/*
+ * "Ode to _OSI(Linux)"
+ *
+ * osi_linux -- Control response to BIOS _OSI(Linux) query.
+ *
+ * As Linux evolves, the features that it supports change.
+ * So an OSI string such as "Linux" is not specific enough
+ * to be useful across multiple versions of Linux.  It
+ * doesn't identify any particular feature, interface,
+ * or even any particular version of Linux...
+ *
+ * Unfortunately, Linux-2.6.22 and earlier responded "yes"
+ * to a BIOS _OSI(Linux) query.  When
+ * a reference mobile BIOS started using it, its use
+ * started to spread to many vendor platforms.
+ * As it is not supportable, we need to halt that spread.
+ *
+ * Today, most BIOS references to _OSI(Linux) are noise --
+ * they have no functional effect and are just dead code
+ * carried over from the reference BIOS.
+ *
+ * The next most common case is that _OSI(Linux) harms Linux,
+ * usually by causing the BIOS to follow paths that are
+ * not tested during Windows validation.
+ *
+ * Finally, there is a short list of platforms
+ * where OSI(Linux) benefits Linux.
+ *
+ * In Linux-2.6.23, OSI(Linux) is first disabled by default.
+ * DMI is used to disable the dmesg warning about OSI(Linux)
+ * on platforms where it is known to have no effect.
+ * But a dmesg warning remains for systems where
+ * we do not know if OSI(Linux) is good or bad for the system.
+ * DMI is also used to enable OSI(Linux) for the machines
+ * that are known to need it.
+ *
+ * BIOS writers should NOT query _OSI(Linux) on future systems.
+ * It will be ignored by default, and to get Linux to
+ * not ignore it will require a kernel source update to
+ * add a DMI entry, or a boot-time "acpi_osi=Linux" invocation.
+ */
+#define OSI_LINUX_ENABLE 0
+
+struct osi_linux {
+        unsigned int    enable:1;
+        unsigned int    dmi:1;
+        unsigned int    cmdline:1;
+        unsigned int    known:1;
+} osi_linux = { OSI_LINUX_ENABLE, 0, 0, 0};
 
 static void __init acpi_request_region (struct acpi_generic_address *addr,
         unsigned int length, char *desc)
@@ -959,13 +1007,37 @@ static int __init acpi_os_name_setup(char *str)
 
 __setup("acpi_os_name=", acpi_os_name_setup);
 
-static void enable_osi_linux(int enable) {
+static void __init set_osi_linux(unsigned int enable)
+{
+        if (osi_linux.enable != enable) {
+                osi_linux.enable = enable;
+                printk(KERN_NOTICE PREFIX "%sed _OSI(Linux)\n",
+                        enable ? "Add": "Delet");
+        }
+        return;
+}
+
+static void __init acpi_cmdline_osi_linux(unsigned int enable)
+{
+        osi_linux.cmdline = 1;  /* cmdline set the default */
+        set_osi_linux(enable);
+
+        return;
+}
+
+void __init acpi_dmi_osi_linux(int enable, const struct dmi_system_id *d)
+{
+        osi_linux.dmi = 1;      /* DMI knows that this box asks OSI(Linux) */
+
+        printk(KERN_NOTICE PREFIX "DMI detected: %s\n", d->ident);
+
+        if (enable == -1)
+                return;
+
+        osi_linux.known = 1;    /* DMI knows which OSI(Linux) default needed */
 
-        if (osi_linux != enable)
-                printk(KERN_INFO PREFIX "%sabled _OSI(Linux)\n",
-                        enable ? "En": "Dis");
+        set_osi_linux(enable);
 
-        osi_linux = enable;
         return;
 }
 
@@ -982,12 +1054,12 @@ static int __init acpi_osi_setup(char *str)
                 printk(KERN_INFO PREFIX "_OSI method disabled\n");
                 acpi_gbl_create_osi_method = FALSE;
         } else if (!strcmp("!Linux", str)) {
-                enable_osi_linux(0);
+                acpi_cmdline_osi_linux(0);      /* !enable */
         } else if (*str == '!') {
                 if (acpi_osi_invalidate(++str) == AE_OK)
                         printk(KERN_INFO PREFIX "Deleted _OSI(%s)\n", str);
         } else if (!strcmp("Linux", str)) {
-                enable_osi_linux(1);
+                acpi_cmdline_osi_linux(1);      /* enable */
         } else if (*osi_additional_string == '\0') {
                 strncpy(osi_additional_string, str, OSI_STRING_LENGTH_MAX);
                 printk(KERN_INFO PREFIX "Added _OSI(%s)\n", str);
@@ -1183,19 +1255,29 @@ acpi_os_validate_interface (char *interface)
         if (!strncmp(osi_additional_string, interface, OSI_STRING_LENGTH_MAX))
                 return AE_OK;
         if (!strcmp("Linux", interface)) {
-                printk(KERN_WARNING PREFIX
-                        "System BIOS is requesting _OSI(Linux)\n");
-                if (acpi_dmi_dump())
-                        printk(KERN_NOTICE PREFIX
-                                "[please extract dmidecode output]\n");
-                printk(KERN_NOTICE PREFIX
-                        "Please send DMI info above to "
-                        "linux-acpi@vger.kernel.org\n");
+
                 printk(KERN_NOTICE PREFIX
-                        "If \"acpi_osi=%sLinux\" works better, "
-                        "please notify linux-acpi@vger.kernel.org\n",
-                        osi_linux ? "!" : "");
-                if(osi_linux)
+                        "BIOS _OSI(Linux) query %s%s\n",
+                        osi_linux.enable ? "honored" : "ignored",
+                        osi_linux.cmdline ? " via cmdline" :
+                        osi_linux.dmi ? " via DMI" : "");
+
+                if (!osi_linux.dmi) {
+                        if (acpi_dmi_dump())
+                                printk(KERN_NOTICE PREFIX
+                                        "[please extract dmidecode output]\n");
+                        printk(KERN_NOTICE PREFIX
+                                "Please send DMI info above to "
+                                "linux-acpi@vger.kernel.org\n");
+                }
+                if (!osi_linux.known && !osi_linux.cmdline) {
+                        printk(KERN_NOTICE PREFIX
+                                "If \"acpi_osi=%sLinux\" works better, "
+                                "please notify linux-acpi@vger.kernel.org\n",
+                                osi_linux.enable ? "!" : "");
+                }
+
+                if (osi_linux.enable)
                         return AE_OK;
         }
         return AE_SUPPORT;