[Qemu-devel] [PATCH] Fix IDE FDC emulation for no media

[Pavel Hrdina]

Hi,
this is the patch to fix incorrect handling of IDE floppy drive controller 
emulation
when no media is present. If the guest is booted without a media then the drive
was not being emulated at all but this patch enables the emulation with no 
media present.

There was a bug in FDC emulation without media. Driver was not able to 
recognize that
there is no media in drive.

This has been tested on both Fedora-16 x86_64 VM and Windows XP VM and the 
behaviour
is as expected, i.e. as follows:

Linux guest (Fedora 16 x86_64) tries "mount /dev/fd0" and exit with error
"mount: /dev/fd0 is not a valid block device" which is the same behavior like
bare metal with real floppy device (you have to load floppy driver at first
using e.g. "modprobe floppy" command).

For Windows XP guest the Windows floppy driver is trying to seek the virtual 
drive
when you want to open it but driver successfully detect that there is no media 
in drive
and then it's asking user to insert floppy media in the drive.

I also tested behavior of this patch if you start guest with "-nodefaults" and 
both
Windows and Linux guests detect only FDC but no drive.

Pavel

This patch has been written with help of specifications from:
http://www.ousob.com/ng/hardware/ngd127.php
http://www.isdaman.com/alsos/hardware/fdc/floppy.htm
http://wiki.osdev.org/Floppy_Disk_Controller

Signed-off-by: Pavel Hrdina <address@hidden>
Signed-off-by: Michal Novotny <address@hidden>
---
 hw/fdc.c |   14 ++++++++++----
 hw/pc.c  |    3 ++-
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/hw/fdc.c b/hw/fdc.c
index a0236b7..6791eff 100644
--- a/hw/fdc.c
+++ b/hw/fdc.c
@@ -179,12 +179,14 @@ static void fd_revalidate(FDrive *drv)
     FDriveRate rate;
 
     FLOPPY_DPRINTF("revalidate\n");
-    if (drv->bs != NULL && bdrv_is_inserted(drv->bs)) {
+    if (drv->bs != NULL) {
         ro = bdrv_is_read_only(drv->bs);
         bdrv_get_floppy_geometry_hint(drv->bs, &nb_heads, &max_track,
                                       &last_sect, drv->drive, &drive, &rate);
-        if (nb_heads != 0 && max_track != 0 && last_sect != 0) {
-            FLOPPY_DPRINTF("User defined disk (%d %d %d)",
+        if (!bdrv_is_inserted(drv->bs)) {
+            FLOPPY_DPRINTF("No media in drive\n");
+        } else if (nb_heads != 0 && max_track != 0 && last_sect != 0) {
+            FLOPPY_DPRINTF("User defined disk (%d %d %d)\n",
                            nb_heads - 1, max_track, last_sect);
         } else {
             FLOPPY_DPRINTF("Floppy disk (%d h %d t %d s) %s\n", nb_heads,
@@ -201,11 +203,12 @@ static void fd_revalidate(FDrive *drv)
         drv->drive = drive;
         drv->media_rate = rate;
     } else {
-        FLOPPY_DPRINTF("No disk in drive\n");
+        FLOPPY_DPRINTF("Drive disabled\n");
         drv->last_sect = 0;
         drv->max_track = 0;
         drv->flags &= ~FDISK_DBL_SIDES;
     }
+
 }
 
 /********************************************************/
@@ -937,6 +940,9 @@ static int fdctrl_media_changed(FDrive *drv)
 
     if (!drv->bs)
         return 0;
+    /* This is needed for driver to detect there is no media in drive */
+    if (!bdrv_is_inserted(drv->bs))
+        return 1;
     if (drv->media_changed) {
         drv->media_changed = 0;
         ret = 1;
diff --git a/hw/pc.c b/hw/pc.c
index 1f5aacb..29a604b 100644
--- a/hw/pc.c
+++ b/hw/pc.c
@@ -382,7 +382,8 @@ void pc_cmos_init(ram_addr_t ram_size, ram_addr_t 
above_4g_mem_size,
     if (floppy) {
         fdc_get_bs(fd, floppy);
         for (i = 0; i < 2; i++) {
-            if (fd[i] && bdrv_is_inserted(fd[i])) {
+            /* If there is no media in a drive, we still have the drive 
present */
+            if (fd[i]) {
                 bdrv_get_floppy_geometry_hint(fd[i], &nb_heads, &max_track,
                                               &last_sect, FDRIVE_DRV_NONE,
                                               &fd_type[i], &rate);
-- 
1.7.7.6