[Qemu-devel] [RFC 2/2] hw/i386/pc: reflect an explicitly created, sole FDC in the CMOS

[Laszlo Ersek]

With the pc-q35-2.4 machine type, if the user creates an ISA FDC manually:

  -device isa-fdc,driveA=drive-fdc0-0-0 \
  -drive file=...,if=none,id=drive-fdc0-0-0,format=raw

then the board-default FDC will be skipped, and only the explicitly
requested FDC will exist. qtree-wise, this is correct; however such an FDC
is currently not registered in the CMOS, because that code is only reached
for the board-default FDC.

The pc_cmos_init_late() one-shot reset handler -- one-shot because the
CMOS is not reprogrammed during warm reset -- should search for a single,
explicitly created ISA FDC device, if there has been no board default, and
reprogram the CMOS if found.

Cc: Jan Tomko <address@hidden>
Cc: John Snow <address@hidden>
Cc: Markus Armbruster <address@hidden>
Cc: Paolo Bonzini <address@hidden>
Reported-by: Jan Tomko <address@hidden>
Suggested-by: Markus Armbruster <address@hidden>
Signed-off-by: Laszlo Ersek <address@hidden>
---
 hw/i386/pc.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 1ca0cdd..47a3082 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -333,8 +333,30 @@ static void pc_cmos_init_floppy(ISADevice *rtc_state, 
ISADevice *floppy)
 typedef struct pc_cmos_init_late_arg {
     ISADevice *rtc_state;
     BusState *idebus[2];
+    ISADevice *board_floppy;
 } pc_cmos_init_late_arg;
 
+typedef struct check_fdc_state {
+    ISADevice *floppy;
+    bool multiple;
+} CheckFdcState;
+
+static int check_fdc(Object *obj, void *opaque)
+{
+    CheckFdcState *state = opaque;
+    Object *fdc;
+
+    fdc = object_dynamic_cast(obj, TYPE_ISA_FDC);
+    if (fdc) {
+        if (state->floppy) {
+            state->multiple = true;
+        } else {
+            state->floppy = ISA_DEVICE(obj);
+        }
+    }
+    return 0;
+}
+
 static void pc_cmos_init_late(void *opaque)
 {
     pc_cmos_init_late_arg *arg = opaque;
@@ -372,6 +394,29 @@ static void pc_cmos_init_late(void *opaque)
     }
     rtc_set_memory(s, 0x39, val);
 
+    /*
+     * If the board initialization code created no FDC, but exactly one FDC has
+     * been created since then explicitly, then we configure the CMOS registers
+     * now, in accordance with that one FDC.
+     */
+    if (arg->board_floppy == NULL) {
+        static const char * const paths[] = { "/peripheral",
+            "/peripheral-anon", NULL };
+        const char * const * path;
+        CheckFdcState state = { 0 };
+
+        for (path = paths; *path; ++path) {
+            Object *container;
+
+            container = container_get(qdev_get_machine(), *path);
+            object_child_foreach(container, check_fdc, &state);
+        }
+
+        if (state.floppy && !state.multiple) {
+            pc_cmos_init_floppy(s, state.floppy);
+        }
+    }
+
     qemu_unregister_reset(pc_cmos_init_late, opaque);
 }
 
@@ -447,6 +492,7 @@ void pc_cmos_init(ram_addr_t ram_size, ram_addr_t 
above_4g_mem_size,
     arg.rtc_state = s;
     arg.idebus[0] = idebus0;
     arg.idebus[1] = idebus1;
+    arg.board_floppy = floppy;
     qemu_register_reset(pc_cmos_init_late, &arg);
 }
 
-- 
1.8.3.1