Hi,

I've done big improvements on floppy drive controller.
For easier reviewing, I've tried to split them up in differents parts. 
Sorry if some parts are still big.
Each patch applies on top of the previous one.

If only some of them are accepted, I can provide a global patch for only 
these ones. Patches which needs more work will be resubmitted later.

List of attached patches:

fdc_01_lookuptable.diff
- Adds a command lookup table, as suggested by Fabrice at 
http://lists.gnu.org/archive/html/qemu-devel/2008-04/msg00143.html
- This also moves initialization functions at the bottom of the file to 
prevent multiple forward declarations.

fdc_02_seek_next_sector.diff
- Extract seeking to next sector handling in a function. Add a sector 
seek in PIO read and write modes

fdc_03_status_ab.diff
- Fixes status A and status B registers. It removes one Sun4m mutation. 
Also removes the internal FD_CTRL_INTR flag.

fdc_04_status_012.diff
- Fixes status0, status1 and status2 handling, which were broken in 
read/write commands and in some subtle ways. Status are now calculated 
during command execution and not at the very end.
- This allows removing of one hack in 
fdctrl_handle_sense_interrupt_status().

fdc_05_dmaen.diff
- Handles correctly FD_MSR_NONDMA/FD_DOR_NONDMA flags, and uses them 
when possible. Fixes a problem with SPECIFY command. This allows 
removing of last Sun4m mutation.

fdc_06_dor_reg.diff
- Better handling of DOR register. DOR register drives external motors, 
but it not limited to existing drives.
- Use FD_DOR_nRESET flag instead of internal FD_CTRL_RESET flag.
- Support writing to DOR register even in reset mode (as said in 
specification)

fdc_07_msr_reg.diff
- Stores controller state in MSR register instead of internal state 
field. This simplifies the fdctrl_read_main_status() function, which may 
be called in some tight loops.

fdc_08_cleanup.diff
- Removes useless fields in fdrive_t structure.
- Adds a message when bdrv_read/bdrv_write calls fail.

fdc_09_tdr_reg.diff
- Replaces bootsel field by the whole tdr register. It may be easier if 
we want to later add support for tapes.

fdc_10_4_fds.diff
- Supports up to 4 floppy drives if MAX_FD is set to 4.

fdc_11_cur_drv.diff
- Replaces access to cur_drv field by macros.

fdc_12_pio_write.diff
- Fixes transfer data length.
- Fixes buffer overflow in PIO mode write.

Floppy controller works better than before in Sun4m. It now gets READ 
commands and correctly detects if floppy is write-protected or not. 
Unfortunately, no valid filesystem seems to be found on the floppy.

Please comment.


Hervé