[RFC,v2] Add option to switch off FDC

diff --git a/qemu-options.hx b/qemu-options.hx
index 56e5fdf..993d377 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1297,6 +1297,14 @@  STEXI
 Disable HPET support.
 ETEXI
 
+DEF("no-fdc", 0, QEMU_OPTION_no_fdc,
+    "-no-fdc         disable FDC\n", QEMU_ARCH_I386)
+STEXI
+@item -no-fdc
+@findex -no-fdc
+Disable FDC support.
+ETEXI
+
 DEF("acpitable", HAS_ARG, QEMU_OPTION_acpitable,
     "-acpitable [sig=str][,rev=n][,oem_id=str][,oem_table_id=str][,oem_rev=n][,asl_compiler_id=str][,asl_compiler_rev=n][,{data|file}=file1[:file2]...]\n"
     "                ACPI table description\n", QEMU_ARCH_I386)
diff --git a/vl.c b/vl.c
index c73462e..ffaa7ae 100644
--- a/vl.c
+++ b/vl.c
@@ -214,6 +214,7 @@  const char *vnc_display;
 #endif
 int acpi_enabled = 1;
 int no_hpet = 0;
+int have_fdc = 1;
 int fd_bootchk = 1;
 static int no_reboot;
 int no_shutdown = 0;
@@ -3581,6 +3582,9 @@  int main(int argc, char **argv, char **envp)
             case QEMU_OPTION_no_hpet:
                 no_hpet = 1;
                 break;
+            case QEMU_OPTION_no_fdc:
+                have_fdc = 0;
+                break;
             case QEMU_OPTION_balloon:
                 if (balloon_parse(optarg) < 0) {
                     fprintf(stderr, "Unknown -balloon argument %s\n", optarg);
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 3e1e81b..db4017b 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -173,6 +173,9 @@  void piix4_smbus_register_device(SMBusDevice *dev, uint8_t addr);
 /* hpet.c */
 extern int no_hpet;
 
+/* fdc.c */
+extern int have_fdc;
+
 /* piix_pci.c */
 struct PCII440FXState;
 typedef struct PCII440FXState PCII440FXState;
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 348b15f..d38e272 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1358,10 +1358,14 @@  void pc_basic_device_init(ISABus *isa_bus, qemu_irq *gsi,
     cpu_exit_irq = qemu_allocate_irqs(cpu_request_exit, NULL, 1);
     DMA_init(0, cpu_exit_irq);
 
-    for(i = 0; i < MAX_FD; i++) {
-        fd[i] = drive_get(IF_FLOPPY, 0, i);
+    if (have_fdc) {
+        for (i = 0; i < MAX_FD; i++) {
+            fd[i] = drive_get(IF_FLOPPY, 0, i);
+        }
+        *floppy = fdctrl_init_isa(isa_bus, fd);
+    } else {
+        *floppy = NULL;
     }
-    *floppy = fdctrl_init_isa(isa_bus, fd);
 }
 
 void pc_nic_init(ISABus *isa_bus, PCIBus *pci_bus)
diff --git a/hw/i386/acpi-dsdt.dsl b/hw/i386/acpi-dsdt.dsl
index b23d5e0..16d3be5 100644
--- a/hw/i386/acpi-dsdt.dsl
+++ b/hw/i386/acpi-dsdt.dsl
@@ -149,11 +149,11 @@  DefinitionBlock (
                 , 3,
                 CBEN, 1,         // COM2
             }
-            Name(FDEN, 1)
         }
     }
 
 #define DSDT_APPLESMC_STA piix_dsdt_applesmc_sta
+#define DSDT_FDC_STA piix_dsdt_fdc_sta
 #include "acpi-dsdt-isa.dsl"
 
 
diff --git a/hw/i386/q35-acpi-dsdt.dsl b/hw/i386/q35-acpi-dsdt.dsl
index d618e9e..0861414 100644
--- a/hw/i386/q35-acpi-dsdt.dsl
+++ b/hw/i386/q35-acpi-dsdt.dsl
@@ -181,13 +181,13 @@  DefinitionBlock (
             Field(LPCE, AnyAcc, NoLock, Preserve) {
                 CAEN,   1,
                 CBEN,   1,
-                LPEN,   1,
-                FDEN,   1
+                LPEN,   1
             }
         }
     }
 
 #define DSDT_APPLESMC_STA q35_dsdt_applesmc_sta
+#define DSDT_FDC_STA q35_dsdt_fdc_sta
 #include "acpi-dsdt-isa.dsl"
 
 
diff --git a/hw/i386/acpi-dsdt-isa.dsl b/hw/i386/acpi-dsdt-isa.dsl
index deb37de..ffe6770 100644
--- a/hw/i386/acpi-dsdt-isa.dsl
+++ b/hw/i386/acpi-dsdt-isa.dsl
@@ -60,14 +60,9 @@  Scope(\_SB.PCI0.ISA) {
 
     Device(FDC0) {
         Name(_HID, EisaId("PNP0700"))
-        Method(_STA, 0, NotSerialized) {
-            Store(FDEN, Local0)
-            If (LEqual(Local0, 0)) {
-                Return (0x00)
-            } Else {
-                Return (0x0F)
-            }
-        }
+        /* _STA will be patched to 0x0F if the FDC is present */
+        ACPI_EXTRACT_NAME_BYTE_CONST DSDT_FDC_STA
+        Name(_STA, 0xF0)
         Name(_CRS, ResourceTemplate() {
             IO(Decode16, 0x03F2, 0x03F2, 0x00, 0x04)
             IO(Decode16, 0x03F7, 0x03F7, 0x00, 0x01)
diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 50e83f3..302a745 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -88,7 +88,7 @@  typedef struct AcpiBuildPciBusHotplugState {
 
 static void acpi_get_dsdt(AcpiMiscInfo *info)
 {
-    uint16_t *applesmc_sta;
+    uint16_t *applesmc_sta, *fdc_sta;
     Object *piix = piix4_pm_find();
     Object *lpc = ich9_lpc_find();
     assert(!!piix != !!lpc);
@@ -97,16 +97,22 @@  static void acpi_get_dsdt(AcpiMiscInfo *info)
         info->dsdt_code = AcpiDsdtAmlCode;
         info->dsdt_size = sizeof AcpiDsdtAmlCode;
         applesmc_sta = piix_dsdt_applesmc_sta;
+        fdc_sta = piix_dsdt_fdc_sta;
     }
     if (lpc) {
         info->dsdt_code = Q35AcpiDsdtAmlCode;
         info->dsdt_size = sizeof Q35AcpiDsdtAmlCode;
         applesmc_sta = q35_dsdt_applesmc_sta;
+        fdc_sta = q35_dsdt_fdc_sta;
     }
 
     /* Patch in appropriate value for AppleSMC _STA */
     *(uint8_t *)(info->dsdt_code + *applesmc_sta) =
         applesmc_find() ? 0x0b : 0x00;
+
+    /* Patch in appropriate value for FDC _STA */
+    *(uint8_t *)(info->dsdt_code + *fdc_sta) =
+        have_fdc ? 0x0f : 0x00;
 }
 
 static