Kernel: Remove "non-operational" ACPI parser state

If we don't support ACPI, just don't instantiate an ACPI parser.
This is way less confusing than having a special parser class whose
only purpose is to do nothing.

We now search for the RSDP in ACPI::initialize() instead of letting
the parser constructor do it. This allows us to defer the decision
to create a parser until we're sure we can make a useful one.

Kernel/ACPI/ACPIDynamicParser.cpp

@@ -30,12 +30,6 @@
 namespace Kernel {
 namespace ACPI {
 
-DynamicParser::DynamicParser()
-    : IRQHandler(9)
-{
-    klog() << "ACPI: Dynamic Parsing Enabled, Can parse AML";
-}
-
 DynamicParser::DynamicParser(PhysicalAddress rsdp)
     : IRQHandler(9)
     , StaticParser(rsdp)

Kernel/ACPI/ACPIDynamicParser.h

@@ -51,8 +51,7 @@ public:
     virtual const char* purpose() const override { return "ACPI Parser"; }
 
 protected:
-    DynamicParser();
-    explicit DynamicParser(PhysicalAddress);
+    explicit DynamicParser(PhysicalAddress rsdp);
 
 private:
     void build_namespace();

Kernel/ACPI/ACPIParser.cpp

@@ -32,10 +32,9 @@ namespace ACPI {
 
 static Parser* s_acpi_parser;
 
-Parser& Parser::the()
+Parser* Parser::the()
 {
-    ASSERT(s_acpi_parser);
-    return *s_acpi_parser;
+    return s_acpi_parser;
 }
 
 void Parser::set_the(Parser& parser)
@@ -44,31 +43,6 @@ void Parser::set_the(Parser& parser)
     s_acpi_parser = &parser;
 }
 
-Parser::Parser(bool usable)
-{
-    if (usable) {
-        klog() << "ACPI: Setting up a functional parser";
-    } else {
-        klog() << "ACPI: Limited Initialization. Vital functions are disabled by a request";
-    }
-}
-
-PhysicalAddress Parser::find_table(const char*)
-{
-    klog() << "ACPI: Requested to search for a table, Abort!";
-    return {};
-}
-
-void Parser::try_acpi_reboot()
-{
-    klog() << "ACPI: Cannot invoke reboot!";
-}
-
-void Parser::try_acpi_shutdown()
-{
-    klog() << "ACPI: Cannot invoke shutdown!";
-}
-
 void Parser::enable_aml_interpretation()
 {
     klog() << "ACPI: No AML Interpretation Allowed";
@@ -99,9 +73,5 @@ const FADTFlags::x86_Specific_Flags& Parser::x86_specific_flags() const
     klog() << "ACPI Limited: x86 specific features cannot be obtained";
     ASSERT_NOT_REACHED();
 }
-bool Parser::is_operable()
-{
-    return false;
-}
 }
 }

Kernel/ACPI/ACPIParser.h

@@ -28,6 +28,7 @@
 
 #include <AK/Types.h>
 #include <Kernel/ACPI/Definitions.h>
+#include <Kernel/ACPI/Initialize.h>
 #include <Kernel/FileSystem/File.h>
 #include <Kernel/VM/Region.h>
 #include <LibBareMetal/Memory/PhysicalAddress.h>
@@ -38,33 +39,31 @@ namespace ACPI {
 
 class Parser {
 public:
-    static Parser& the();
+    static Parser* the();
 
     template<typename ParserType>
-    static void initialize()
+    static void initialize(PhysicalAddress rsdp)
     {
-        set_the(*new ParserType);
+        set_the(*new ParserType(rsdp));
     }
 
-    virtual PhysicalAddress find_table(const char* sig);
+    virtual PhysicalAddress find_table(const char* sig) = 0;
 
-    virtual void try_acpi_reboot();
-    virtual bool can_reboot() { return false; }
-    virtual void try_acpi_shutdown();
-    virtual bool can_shutdown() { return false; }
+    virtual void try_acpi_reboot() = 0;
+    virtual bool can_reboot() = 0;
+    virtual void try_acpi_shutdown() = 0;
+    virtual bool can_shutdown() = 0;
 
-    virtual const FADTFlags::HardwareFeatures& hardware_features() const;
-    virtual const FADTFlags::x86_Specific_Flags& x86_specific_flags() const;
+    virtual const FADTFlags::HardwareFeatures& hardware_features() const = 0;
+    virtual const FADTFlags::x86_Specific_Flags& x86_specific_flags() const = 0;
 
     virtual void enable_aml_interpretation();
     virtual void enable_aml_interpretation(File&);
     virtual void enable_aml_interpretation(u8*, u32);
     virtual void disable_aml_interpretation();
-    virtual bool is_operable();
 
 protected:
-    explicit Parser(bool usable = false);
-    bool m_operable;
+    Parser() {}
 
 private:
     static void set_the(Parser&);

Kernel/ACPI/ACPIStaticParser.cpp

@@ -324,26 +324,10 @@ void StaticParser::locate_main_system_description_table()
     }
 }
 
-StaticParser::StaticParser()
-    : Parser(true)
-    , m_rsdp(StaticParsing::search_rsdp())
-{
-    if (!m_rsdp.is_null()) {
-        klog() << "ACPI: Using RSDP @ " << m_rsdp;
-        m_operable = true;
-        locate_static_data();
-    } else {
-        m_operable = false;
-        klog() << "ACPI: Disabled, due to RSDP being absent";
-    }
-}
-
 StaticParser::StaticParser(PhysicalAddress rsdp)
-    : Parser(true)
-    , m_rsdp(rsdp)
+    : m_rsdp(rsdp)
 {
     klog() << "ACPI: Using RSDP @ " << rsdp;
-    m_operable = true;
     locate_static_data();
 }
 

Kernel/ACPI/ACPIStaticParser.h

@@ -41,14 +41,12 @@ public:
     virtual bool can_reboot() override;
     virtual bool can_shutdown() override { return false; }
     virtual void try_acpi_shutdown() override;
-    virtual bool is_operable() override { return m_operable; }
 
     virtual const FADTFlags::HardwareFeatures& hardware_features() const override;
     virtual const FADTFlags::x86_Specific_Flags& x86_specific_flags() const override;
 
 protected:
-    StaticParser();
-    explicit StaticParser(PhysicalAddress);
+    explicit StaticParser(PhysicalAddress rsdp);
 
 private:
     void locate_static_data();

Kernel/ACPI/Initialize.cpp

@@ -49,17 +49,23 @@ static FeatureLevel determine_feature_level()
 
 void initialize()
 {
-    switch (determine_feature_level()) {
-    case FeatureLevel::Enabled:
-        Parser::initialize<DynamicParser>();
-        break;
-    case FeatureLevel::Limited:
-        Parser::initialize<StaticParser>();
-        break;
-    case FeatureLevel::Disabled:
-        Parser::initialize<Parser>();
-        break;
-    }
+    auto feature_level = determine_feature_level();
+    if (feature_level == FeatureLevel::Disabled)
+        return;
+
+    auto rsdp = StaticParsing::search_rsdp();
+    if (rsdp.is_null())
+        return;
+
+    if (feature_level == FeatureLevel::Enabled)
+        Parser::initialize<DynamicParser>(rsdp);
+    else
+        Parser::initialize<StaticParser>(rsdp);
+}
+
+bool is_enabled()
+{
+    return Parser::the();
 }
 
 }

Kernel/ACPI/Initialize.h

@@ -29,6 +29,7 @@
 namespace Kernel {
 namespace ACPI {
 
+bool is_enabled();
 void initialize();
 
 }