AltairZ80: wd179x: Better support for 5.25-inch floppies.

[hharte]

AltairZ80: wd179x: Better support for 5.25-inch floppies.

Summary

Allow wd179x to support both 360 RPM (8") and 300 RPM (5.25") drives.

Compiled with:

• VS 2022 17.14.12 - vcxproj
• MSVC 19.44.35214.0 - CMake
• MacOS (x64) clang-1700.0.13.5
• Linux gcc 12.2.0-14

Automated tests:

SIMH running on Windows, Linux (ARM), MacOS (x64):

CompuPro CP/M-80
CompuPro CP/M-86
SCP 86-DOS
MS-DOS 2.11 - Builds MS-DOS 2.11 from source.
CompuPro CP/M-68K v1.3 (68000 and 68010 versions)
CP/M-68K v1.2
Advanced Digital Super-Six CP/M 2.2
Advanced Digital Super-Six CP/M 3.0
DIGITEX CP/M 2.2
DIGITEX CP/M 3.0
DIGITEX OASIS multi-user version 5.6
MultiStar: IBC OASIS multi-user version 5.6
MegaStar: IBC OASIS multi-user version 5.6
CP/M-80 (Altair) ZEXALL Z80 instruction set test.
CP/M 3 (Altair) Banked Memory Test.

FYI, @psco, @deltecent

[markpizz]

@psco does this look good to you?

[psco]

Thank you Howard, this looks fine and can be merged.

[deltecent]

@hharte would you please remind me how to do those automated tests? I have PR coming that also changes wd179x.c.

[deltecent]

Found it! altairz80-tests.

[pmetzger]

I'm also putting this into ZIMH, along with a bunch of tests. Thanks for the changes!

[pmetzger]

FYI, in your patch, wd179x_set_rpm() checks if (wd179x_info->sel_drive > WD179X_MAX_DRIVES) and then writes to drive[sel_drive & 3].

Since valid drives are 0..WD179X_MAX_DRIVES - 1, the guard should reject sel_drive >= WD179X_MAX_DRIVES. As written,sel_drive == WD179X_MAX_DRIVES is accepted and wrapped to drive 0 by & 3, and larger invalid values are also masked if they pass future changes. The setter should either return on >= WD179X_MAX_DRIVES and index with sel_drive.

I've fixed this in my fork.