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[Qemu-devel] [PATCH 1/8] vpc: detect floppy disk geometries
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 1/8] vpc: detect floppy disk geometries |
Date: |
Wed, 19 Oct 2011 16:59:51 +0200 |
Converting a floppy image from RAW to VPC and back will generate
a zero-padded file of the wrong size, because the geometry is not
computed correctly. Special case floppy disk images, handling
standard MS-DOS capacities (160/180/320/360 for low density
5.25" disks, 1200 for high density 5.25" disks, 720/1440/2880
for 3.5" disks).
Signed-off-by: Paolo Bonzini <address@hidden>
---
block/vpc.c | 8 ++++++++
1 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/block/vpc.c b/block/vpc.c
index cb6c570..549a632 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -463,6 +463,14 @@ static int calculate_geometry(int64_t total_sectors,
uint16_t* cyls,
{
uint32_t cyls_times_heads;
+ if (total_sectors <= 5760) {
+ /* Floppy disk geometry */
+ *heads = total_sectors < 640 ? 1 : 2; /* 1 = single side 5.25" */
+ *cyls = total_sectors < 1440 ? 40 : 80; /* 40 = low density 5.25" */
+ *secs_per_cyl = total_sectors / *heads / *cyls;
+ return 0;
+ }
+
if (total_sectors > 65535 * 16 * 255)
return -EFBIG;
--
1.7.6