On some laptop models (e.g. Dell Vostro V131), WMI events are not
generated until a specific SMBIOS request is issued to register an event
listener [1].  As there seems to be no ACPI method or SMBIOS request to
determine without possible side effects whether a given machine needs to
issue this SMBIOS request in order to receive WMI events, DMI matching
is used to whitelist the models which need it.

[1] https://lists.us.dell.com/pipermail/libsmbios-devel/2015-July/000612.html

Signed-off-by: Michał Kępień <ker...@kempniu.pl>
---
 drivers/platform/x86/Kconfig    |    1 +
 drivers/platform/x86/dell-wmi.c |   49 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index 3e4d9c3..5ceb53a 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig
@@ -122,6 +122,7 @@ config DELL_WMI
        depends on ACPI_WMI
        depends on INPUT
        depends on ACPI_VIDEO || ACPI_VIDEO = n
+       depends on DELL_SMBIOS
        select INPUT_SPARSEKMAP
        ---help---
          Say Y here if you want to support WMI-based hotkeys on Dell laptops.
diff --git a/drivers/platform/x86/dell-wmi.c b/drivers/platform/x86/dell-wmi.c
index 368e193..ca8233a 100644
--- a/drivers/platform/x86/dell-wmi.c
+++ b/drivers/platform/x86/dell-wmi.c
@@ -37,6 +37,7 @@
 #include <linux/string.h>
 #include <linux/dmi.h>
 #include <acpi/video.h>
+#include "dell-smbios.h"
 
 MODULE_AUTHOR("Matthew Garrett <m...@redhat.com>");
 MODULE_AUTHOR("Pali Rohár <pali.ro...@gmail.com>");
@@ -47,10 +48,29 @@ MODULE_LICENSE("GPL");
 #define DELL_DESCRIPTOR_GUID "8D9DDCBC-A997-11DA-B012-B622A1EF5492"
 
 static u32 dell_wmi_interface_version;
+static bool wmi_requires_smbios_request;
 
 MODULE_ALIAS("wmi:"DELL_EVENT_GUID);
 MODULE_ALIAS("wmi:"DELL_DESCRIPTOR_GUID);
 
+static int __init dmi_matched(const struct dmi_system_id *dmi)
+{
+       wmi_requires_smbios_request = 1;
+       return 1;
+}
+
+static const struct dmi_system_id dell_wmi_smbios_list[] __initconst = {
+       {
+               .callback = dmi_matched,
+               .ident = "Dell Vostro V131",
+               .matches = {
+                       DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+                       DMI_MATCH(DMI_PRODUCT_NAME, "Vostro V131"),
+               },
+       },
+       { }
+};
+
 /*
  * Certain keys are flagged as KE_IGNORE. All of these are either
  * notifications (rather than requests for change) or are also sent
@@ -513,6 +533,7 @@ static int __init dell_wmi_init(void)
 {
        int err;
        acpi_status status;
+       struct calling_interface_buffer *buffer;
 
        if (!wmi_has_guid(DELL_EVENT_GUID) ||
            !wmi_has_guid(DELL_DESCRIPTOR_GUID)) {
@@ -538,12 +559,40 @@ static int __init dell_wmi_init(void)
                return -ENODEV;
        }
 
+       dmi_check_system(dell_wmi_smbios_list);
+
+       if (wmi_requires_smbios_request) {
+               buffer = dell_smbios_get_buffer();
+               buffer->input[0] = 0x10000;
+               buffer->input[1] = 0x51534554;
+               buffer->input[3] = 0x1;
+               dell_smbios_send_request(17, 3);
+               err = buffer->output[0];
+               dell_smbios_release_buffer();
+               if (err) {
+                       pr_err("Failed to enable WMI (error %d)\n", err);
+                       wmi_remove_notify_handler(DELL_EVENT_GUID);
+                       dell_wmi_input_destroy();
+                       return dell_smbios_error(err);
+               }
+       }
+
        return 0;
 }
 module_init(dell_wmi_init);
 
 static void __exit dell_wmi_exit(void)
 {
+       struct calling_interface_buffer *buffer;
+
+       if (wmi_requires_smbios_request) {
+               buffer = dell_smbios_get_buffer();
+               buffer->input[0] = 0x10000;
+               buffer->input[1] = 0x51534554;
+               dell_smbios_send_request(17, 3);
+               dell_smbios_release_buffer();
+       }
+
        wmi_remove_notify_handler(DELL_EVENT_GUID);
        dell_wmi_input_destroy();
 }
-- 
1.7.10.4

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