HotSwap IDE: PIO possible; DMA not

Its ALMOST possible to hotswap IDE drives, which make nice backup devices for raid filesystems. Unfortunately, once the .../ide/pci/*.o chipset-specific module is installed, it becomes wedged with the ide-core module, making further substitutions impossible without a reboot. Although it works fine PIO, see below, it would sure be nice to solve this problem and get it working DMA.

Maybe the "Y" config option for the .../ide/pci/*.o modules should link them into the ide-core.o module, if "M" has been selected for ide-core (formerly ide-mod), because now the "Y" options doesn't link them anywhere, and probably shouldn't even be allowed, once ide-core is "M."

In /etc/modules.conf:
...
alias hd ide-disk
###below ide-disk ide-detect ide-core serverworks below ide-disk ide-detect ide-core
...

-bash-2.05b# lsmod
Module Size Used by Not tainted

sd_mod                 12588   0  (autoclean) (unused)
3w-xxxx                40288   0  (unused)
scsi_mod              101812   2  [sd_mod 3w-xxxx]

-bash-2.05b# fdisk -l /dev/hda
(insert 40 GB disk at this time)
-bash-2.05b# modprobe hd
-bash-2.05b# fdisk -l /dev/hda

Disk /dev/hda: 40.0 GB, 40027029504 bytes
255 heads, 63 sectors/track, 4866 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System

/dev/hda1   *         1        16    128488+  83  Linux
/dev/hda2            17       147   1052257+  82  Linux swap
/dev/hda3           148      4866  37905367+  83  Linux

-bash-2.05b# hdparm /dev/hda

/dev/hda:

multcount    = 16 (on)
IO_support   =  0 (default 16-bit)
unmaskirq    =  0 (off)
using_dma    =  0 (off)
keepsettings =  0 (off)
readonly     =  0 (off)
readahead    =  8 (on)
geometry     = 4866/255/63, sectors = 78177792, start = 0
-bash-2.05b# lsmod
Module                  Size  Used by    Not tainted
ide-disk               18784   0
ide-detect               680   0  (unused)
ide-core              149296   0  [ide-disk ide-detect]
sd_mod                 12588   2  (autoclean)
3w-xxxx                40288   1
scsi_mod              101812   2  [sd_mod 3w-xxxx]

-bash-2.05b# modprobe -r hd
-bash-2.05b# fdisk -l /dev/hda
(remove 40 GB disk and insert 60 GB disk at this time) -bash-2.05b# modprobe hd
-bash-2.05b# fdisk -l

Disk /dev/hda: 61.4 GB, 61492838400 bytes
255 heads, 63 sectors/track, 7476 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/hda1 1 7476 60050938+ 83 Linux
-bash-2.05b# hdparm /dev/hda

/dev/hda:

multcount    = 16 (on)
IO_support   =  0 (default 16-bit)
unmaskirq    =  0 (off)
using_dma    =  0 (off)
keepsettings =  0 (off)
readonly     =  0 (off)
readahead    =  8 (on)

geometry = 7476/255/63, sectors = 120103200, start = 0
-bash-2.05b# hdparm -d 1 /dev/hda

/dev/hda:
setting using_dma to 1 (on)
HDIO_SET_DMA failed: Operation not permitted
using_dma = 0 (off)
-bash-2.05b# insmod serverworks
Using /lib/modules/2.4.24/kernel/drivers/ide/pci/serverworks.o -bash-2.05b# hdparm -d 1 /dev/hda

/dev/hda:
setting using_dma to 1 (on)
using_dma = 1 (on)
-bash-2.05b# lsmod
Module Size Used by Not tainted

serverworks            10552   1
ide-disk               18784   0
ide-detect               680   0  (unused)
ide-core              149296   0  [serverworks ide-disk ide-detect]
sd_mod                 12588   2  (autoclean)
3w-xxxx                40288   1
scsi_mod              101812   2  [sd_mod 3w-xxxx]
-bash-2.05b# rmmod ide-disk ide-detect
-bash-2.05b# lsmod
Module                  Size  Used by    Not tainted
serverworks            10552   1
ide-core              149296   0  [serverworks]
sd_mod                 12588   2  (autoclean)
3w-xxxx                40288   1
scsi_mod              101812   2  [sd_mod 3w-xxxx]

-bash-2.05b# rmmod ide-core
ide-core: Device or resource busy
-bash-2.05b# rmmod serverworks
serverworks: Device or resource busy
-bash-2.05b#

--Fred