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[Qemu-devel] [PULL 11/13] fdc: rework pick_geometry
From: |
John Snow |
Subject: |
[Qemu-devel] [PULL 11/13] fdc: rework pick_geometry |
Date: |
Mon, 25 Jan 2016 14:41:23 -0500 |
This one is the crazy one.
fd_revalidate currently uses pick_geometry to tell if the diskette
geometry has changed upon an eject/insert event, but it won't allow us
to insert a 1.44MB diskette into a 2.88MB drive. This is inflexible.
The new algorithm applies a new heuristic to guessing disk geometries
that allows us to switch diskette types as long as the physical size
matches before falling back to the old heuristic.
The old one is roughly:
- If the size (sectors) and type matches, choose it.
- Fall back to the first geometry that matched our type.
The new one is:
- If the size (sectors) and type matches, choose it.
- If the size (sectors) and physical size match, choose it.
- Fall back to the first geometry that matched our type.
Signed-off-by: John Snow <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
Message-id: address@hidden
---
hw/block/fdc.c | 72 ++++++++++++++++++++++++++++++++++++++++++----------------
1 file changed, 52 insertions(+), 20 deletions(-)
diff --git a/hw/block/fdc.c b/hw/block/fdc.c
index e51154b..6e0c5fc 100644
--- a/hw/block/fdc.c
+++ b/hw/block/fdc.c
@@ -125,7 +125,6 @@ static const FDFormat fd_formats[] = {
{ FLOPPY_DRIVE_TYPE_NONE, -1, -1, 0, 0, },
};
-__attribute__((__unused__))
static FDriveSize drive_size(FloppyDriveType drive)
{
switch (drive) {
@@ -284,45 +283,78 @@ static int pick_geometry(FDrive *drv)
BlockBackend *blk = drv->blk;
const FDFormat *parse;
uint64_t nb_sectors, size;
- int i, first_match, match;
+ int i;
+ int match, size_match, type_match;
+ bool magic = drv->drive == FLOPPY_DRIVE_TYPE_AUTO;
/* We can only pick a geometry if we have a diskette. */
if (!drv->media_inserted || drv->drive == FLOPPY_DRIVE_TYPE_NONE) {
return -1;
}
+ /* We need to determine the likely geometry of the inserted medium.
+ * In order of preference, we look for:
+ * (1) The same drive type and number of sectors,
+ * (2) The same diskette size and number of sectors,
+ * (3) The same drive type.
+ *
+ * In all cases, matches that occur higher in the drive table will take
+ * precedence over matches that occur later in the table.
+ */
blk_get_geometry(blk, &nb_sectors);
- match = -1;
- first_match = -1;
+ match = size_match = type_match = -1;
for (i = 0; ; i++) {
parse = &fd_formats[i];
if (parse->drive == FLOPPY_DRIVE_TYPE_NONE) {
break;
}
- if (drv->drive == parse->drive ||
- drv->drive == FLOPPY_DRIVE_TYPE_AUTO) {
- size = (parse->max_head + 1) * parse->max_track *
- parse->last_sect;
- if (nb_sectors == size) {
- match = i;
- break;
+ size = (parse->max_head + 1) * parse->max_track * parse->last_sect;
+ if (nb_sectors == size) {
+ if (magic || parse->drive == drv->drive) {
+ /* (1) perfect match -- nb_sectors and drive type */
+ goto out;
+ } else if (drive_size(parse->drive) == drive_size(drv->drive)) {
+ /* (2) size match -- nb_sectors and physical medium size */
+ match = (match == -1) ? i : match;
+ } else {
+ /* This is suspicious -- Did the user misconfigure? */
+ size_match = (size_match == -1) ? i : size_match;
}
- if (first_match == -1) {
- first_match = i;
+ } else if (type_match == -1) {
+ if ((parse->drive == drv->drive) ||
+ (magic && (parse->drive == get_fallback_drive_type(drv)))) {
+ /* (3) type match -- nb_sectors mismatch, but matches the type
+ * specified explicitly by the user, or matches the
fallback
+ * default type when using the drive autodetect mechanism
*/
+ type_match = i;
}
}
}
+
+ /* No exact match found */
if (match == -1) {
- if (first_match == -1) {
- error_setg(&error_abort, "No candidate geometries present in table
"
- " for floppy drive type '%s'",
- FloppyDriveType_lookup[drv->drive]);
- } else {
- match = first_match;
+ if (size_match != -1) {
+ parse = &fd_formats[size_match];
+ FLOPPY_DPRINTF("User requested floppy drive type '%s', "
+ "but inserted medium appears to be a "
+ "%d sector '%s' type\n",
+ FloppyDriveType_lookup[drv->drive],
+ nb_sectors,
+ FloppyDriveType_lookup[parse->drive]);
}
- parse = &fd_formats[match];
+ match = type_match;
}
+ /* No match of any kind found -- fd_format is misconfigured, abort. */
+ if (match == -1) {
+ error_setg(&error_abort, "No candidate geometries present in table "
+ " for floppy drive type '%s'",
+ FloppyDriveType_lookup[drv->drive]);
+ }
+
+ parse = &(fd_formats[match]);
+
+ out:
if (parse->max_head == 0) {
drv->flags &= ~FDISK_DBL_SIDES;
} else {
--
2.4.3
- [Qemu-devel] [PULL 00/13] IDE & FDC patches, John Snow, 2016/01/25
- [Qemu-devel] [PULL 02/13] fdc: move pick_geometry, John Snow, 2016/01/25
- [Qemu-devel] [PULL 03/13] fdc: reduce number of pick_geometry arguments, John Snow, 2016/01/25
- [Qemu-devel] [PULL 12/13] qtest/fdc: Support for 2.88MB drives, John Snow, 2016/01/25
- [Qemu-devel] [PULL 01/13] ide: Correct the CHS 'cyls_max' limit to be 65535, John Snow, 2016/01/25
- [Qemu-devel] [PULL 13/13] fdc: change auto fallback drive for ISA FDC to 288, John Snow, 2016/01/25
- [Qemu-devel] [PULL 06/13] fdc: Throw an assertion on misconfigured fd_formats table, John Snow, 2016/01/25
- [Qemu-devel] [PULL 07/13] fdc: add pick_drive, John Snow, 2016/01/25
- [Qemu-devel] [PULL 10/13] fdc: add physical disk sizes, John Snow, 2016/01/25
- [Qemu-devel] [PULL 11/13] fdc: rework pick_geometry,
John Snow <=
- [Qemu-devel] [PULL 08/13] fdc: Add fallback option, John Snow, 2016/01/25
- [Qemu-devel] [PULL 05/13] fdc: add disk field, John Snow, 2016/01/25
- [Qemu-devel] [PULL 09/13] fdc: add drive type option, John Snow, 2016/01/25
- [Qemu-devel] [PULL 04/13] fdc: add drive type qapi enum, John Snow, 2016/01/25
- Re: [Qemu-devel] [PULL 00/13] IDE & FDC patches, Peter Maydell, 2016/01/26