floppy: detect the format from image size instead of always reporting 1.44MB

CMakeLists.txt

@@ -146,6 +146,7 @@ set(SCSI2SD_SOURCES
     lib/SCSI2SD/src/firmware/network.c
     lib/SCSI2SD/src/firmware/vendor.c
     lib/SCSI2SD/src/firmware/geometry.c
+    lib/SCSI2SD/src/firmware/floppy.c
     lib/SCSI2SD/src/firmware/mo.c
     lib/SCSI2SD/src/firmware/AmigaWIFI/AmigaWIFI.c
 )

lib/BlueSCSI_platform_RP2MCU/rp2040-template.ld

@@ -179,6 +179,8 @@ SECTIONS
         *(.text*extractFileName*)
         *(.text*setNameFromImage*)
         *(.text*getBlockSize*)
+        *(.text*s2s_floppy*)
+        *(.text*find_floppy_geometry*)
 
         /* Wi-Fi association, only used during init and reconnect. Keeps the
          * packet path (platform_network_send/receive) in RAM. */

lib/SCSI2SD/src/firmware/floppy.c

@@ -0,0 +1,55 @@
+//	Copyright (c) 2026 Eric Helgeson <eric@bluescsi.com>
+//
+//	This file is part of BlueSCSI.
+//
+//	BlueSCSI is free software: you can redistribute it and/or modify
+//	it under the terms of the GNU General Public License as published by
+//	the Free Software Foundation, either version 3 of the License, or
+//	(at your option) any later version.
+//
+//	BlueSCSI is distributed in the hope that it will be useful,
+//	but WITHOUT ANY WARRANTY; without even the implied warranty of
+//	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//	GNU General Public License for more details.
+//
+//	You should have received a copy of the GNU General Public License
+//	along with BlueSCSI.  If not, see <http://www.gnu.org/licenses/>.
+#include "floppy.h"
+
+#include <stddef.h>
+
+// Transfer rates are the SCSI-2 table 159 values, medium types table 153.
+// Table 153 has one 90mm code (1Eh), so every 3.5" format shares it.
+static const S2S_FloppyFormat FloppyFormats[] =
+{
+	//  blocks  bps  rate    cyl   h  spt  medium  name
+	{      800, 512, 0x00FA,  80,  1, 10, 0x01, "400K" },
+	{      720, 512, 0x00FA,  40,  2,  9, 0x12, "360K" },
+	{     1280, 512, 0x00FA,  80,  2,  8, 0x1E, "640K" },
+	{     1440, 512, 0x00FA,  80,  2,  9, 0x1E, "720K" },
+	{     1600, 512, 0x00FA,  80,  2, 10, 0x1E, "800K" },
+	{     2400, 512, 0x01F4,  80,  2, 15, 0x1A, "1.2M" },
+	{     2880, 512, 0x01F4,  80,  2, 18, 0x1E, "1.44M" },
+	{     5760, 512, 0x03E8,  80,  2, 36, 0x1E, "2.88M" },
+	// NEC 2HD, used by PC-98 and X68000. Shipped in both 5.25" and 3.5".
+	{     1232, 1024, 0x01F4, 77,  2,  8, 0x1E, "1.2M NEC" },
+};
+
+const S2S_FloppyFormat* s2s_floppyFormat(uint32_t blocks, uint16_t bytesPerSector)
+{
+	size_t i;
+	for (i = 0; i < sizeof(FloppyFormats) / sizeof(FloppyFormats[0]); i++)
+	{
+		if (FloppyFormats[i].blocks == blocks &&
+			FloppyFormats[i].bytesPerSector == bytesPerSector)
+		{
+			return &FloppyFormats[i];
+		}
+	}
+	return NULL;
+}
+
+uint8_t s2s_floppyMediumType(uint8_t heads)
+{
+	return (heads > 1) ? 0x02 : 0x01;
+}

lib/SCSI2SD/src/firmware/floppy.h

@@ -0,0 +1,49 @@
+//	Copyright (c) 2026 Eric Helgeson <eric@bluescsi.com>
+//
+//	This file is part of BlueSCSI.
+//
+//	BlueSCSI is free software: you can redistribute it and/or modify
+//	it under the terms of the GNU General Public License as published by
+//	the Free Software Foundation, either version 3 of the License, or
+//	(at your option) any later version.
+//
+//	BlueSCSI is distributed in the hope that it will be useful,
+//	but WITHOUT ANY WARRANTY; without even the implied warranty of
+//	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//	GNU General Public License for more details.
+//
+//	You should have received a copy of the GNU General Public License
+//	along with BlueSCSI.  If not, see <http://www.gnu.org/licenses/>.
+#ifndef S2S_FLOPPY_H
+#define S2S_FLOPPY_H
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct
+{
+	uint32_t blocks;
+	uint16_t bytesPerSector;
+	uint16_t transferRate;	// SCSI-2 table 159
+	uint16_t cylinders;
+	uint8_t heads;
+	uint8_t sectorsPerTrack;
+	uint8_t mediumType;		// SCSI-2 table 153
+	const char* name;
+} S2S_FloppyFormat;
+
+// Match an image against the known floppy formats by size.
+// Returns NULL when the size is not a standard floppy.
+const S2S_FloppyFormat* s2s_floppyFormat(uint32_t blocks, uint16_t bytesPerSector);
+
+// Medium type for an image that matched no format, from its head count.
+uint8_t s2s_floppyMediumType(uint8_t heads);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

lib/SCSI2SD/src/firmware/mode.c

@@ -23,6 +23,7 @@
 #include "mode.h"
 #include "disk.h"
 #include "inquiry.h"
+#include "floppy.h"
 #include "BlueSCSI_mode.h"
 #include "bluescsi_toolbox.h"
 
@@ -146,13 +147,13 @@ static const uint8_t FlexibleDiskDriveGeometry[] =
 {
 0x05, // Page code
 0x1E, // Page length
-0x01, 0xF4, // Transfer Rate (500kbits)
-0x01, // heads
-18, // sectors per track
-0x20,0x00, // bytes per sector
-0x00, 80, // Cylinders
-0x00, 0x80, // Write-precomp
-0x00, 0x80, // reduced current,
+0x00, 0x00, // Transfer Rate
+0x00, // heads
+0x00, // sectors per track
+0x00, 0x00, // bytes per sector
+0x00, 0x00, // Cylinders
+0x00, 0x00, // Write-precomp (set to the cylinder count = disabled)
+0x00, 0x00, // reduced current (set to the cylinder count = disabled)
 0x00, 0x00, // Drive step rate
 0x00, // pulse width
 0x00, 0x00, // Head settle delay
@@ -308,6 +309,47 @@ static void pageIn(int pc, int dataIdx, const uint8_t* pageData, int pageLen)
 	}
 }
 
+typedef struct
+{
+	uint16_t transferRate;
+	uint16_t cylinders;
+	uint16_t bytesPerSector;
+	uint8_t heads;
+	uint8_t sectorsPerTrack;
+	uint8_t mediumType;
+} FloppyGeometry;
+
+// Describe the mounted image rather than a fixed 1.44MB disk. The configured
+// geometry wins so an explicit INI SectorsPerTrack/HeadsPerCylinder still
+// applies; the size match only supplies the transfer rate and medium type.
+static void getFloppyGeometry(FloppyGeometry* geo)
+{
+	uint16_t bytesPerSector = scsiDev.target->liveCfg.bytesPerSector;
+	uint32_t blocks = scsiDev.target->cfg->scsiSectors;
+	const S2S_FloppyFormat* format = s2s_floppyFormat(blocks, bytesPerSector);
+
+	geo->bytesPerSector = bytesPerSector;
+	geo->heads = scsiDev.target->cfg->headsPerCylinder;
+	geo->sectorsPerTrack = scsiDev.target->cfg->sectorsPerTrack;
+
+	if (format)
+	{
+		geo->transferRate = format->transferRate;
+		geo->mediumType = format->mediumType;
+		if (geo->heads == 0) geo->heads = format->heads;
+		if (geo->sectorsPerTrack == 0) geo->sectorsPerTrack = format->sectorsPerTrack;
+	}
+	else
+	{
+		geo->transferRate = 0x01F4;
+		geo->mediumType = s2s_floppyMediumType(geo->heads);
+	}
+
+	uint32_t track = (uint32_t)geo->heads * geo->sectorsPerTrack;
+	uint32_t cylinders = track ? (blocks / track) : 0;
+	geo->cylinders = (cylinders > 0xFFFF) ? 0xFFFF : (uint16_t)cylinders;
+}
+
 static void doModeSense(
 	int sixByteCmd, int dbd, int pc, int pageCode, int allocLength)
 {
@@ -318,6 +360,12 @@ static void doModeSense(
 	int idx = 1;
 	if (!sixByteCmd) ++idx;
 
+	FloppyGeometry floppyGeo = {0};
+	if (scsiDev.target->cfg->deviceType == S2S_CFG_FLOPPY_14MB)
+	{
+		getFloppyGeometry(&floppyGeo);
+	}
+
 	uint8_t mediumType = 0;
 	uint8_t deviceSpecificParam = 0;
 	uint8_t density = 0;
@@ -334,7 +382,7 @@ static void doModeSense(
 		break;
 
 	case S2S_CFG_FLOPPY_14MB:
-		mediumType = 0x1E; // 90mm/3.5"
+		mediumType = floppyGeo.mediumType;
 		deviceSpecificParam =
 			(blockDev.state & DISK_WP) ? 0x80 : 0;
 		density = 0; // reserved for direct access
@@ -571,6 +619,21 @@ static void doModeSense(
 	{
 		pageFound = 1;
 		pageIn(pc, idx, FlexibleDiskDriveGeometry, sizeof(FlexibleDiskDriveGeometry));
+
+		if (pc != 0x01)
+		{
+			scsiDev.data[idx+2] = floppyGeo.transferRate >> 8;
+			scsiDev.data[idx+3] = floppyGeo.transferRate & 0xFF;
+			scsiDev.data[idx+4] = floppyGeo.heads;
+			scsiDev.data[idx+5] = floppyGeo.sectorsPerTrack;
+			scsiDev.data[idx+6] = floppyGeo.bytesPerSector >> 8;
+			scsiDev.data[idx+7] = floppyGeo.bytesPerSector & 0xFF;
+			scsiDev.data[idx+8] = floppyGeo.cylinders >> 8;
+			scsiDev.data[idx+9] = floppyGeo.cylinders & 0xFF;
+			memcpy(&scsiDev.data[idx+10], &scsiDev.data[idx+8], 2);
+			memcpy(&scsiDev.data[idx+12], &scsiDev.data[idx+8], 2);
+		}
+
 		idx += sizeof(FlexibleDiskDriveGeometry);
 	}
 

src/BlueSCSI.cpp

@@ -240,7 +240,7 @@ static const char * typeToChar(int deviceType)
     case S2S_CFG_FIXED:
       return "Fixed";
     case S2S_CFG_FLOPPY_14MB:
-      return "Floppy1.4MB";
+      return "Floppy";
     case S2S_CFG_MO:
       return "MO";
     case S2S_CFG_NETWORK:

src/BlueSCSI_disk.cpp

@@ -28,6 +28,7 @@
 // It is derived from disk.c in SCSI2SD V6.
 
 #include "BlueSCSI_disk.h"
+#include "floppy.h"
 #include "BlueSCSI_log.h"
 #include "BlueSCSI_config.h"
 #include "BlueSCSI_settings.h"
@@ -400,6 +401,28 @@ static bool find_chs_capacity(uint64_t lba, uint16_t max_cylinders, uint8_t min_
     return found_chs;
 }
 
+// Match a floppy image against the standard formats by size so the geometry
+// and MODE SENSE page 05h describe the disk that is actually mounted.
+static bool find_floppy_geometry(image_config_t &img, uint16_t &c, uint8_t &h, uint8_t &s)
+{
+    if (img.deviceType != S2S_CFG_FLOPPY_14MB)
+        return false;
+
+    const S2S_FloppyFormat *format = s2s_floppyFormat(img.scsiSectors, img.bytesPerSector);
+    if (!format)
+    {
+        logmsg("---- WARNING: ", (int)img.scsiSectors, " x ", (int)img.bytesPerSector,
+               " byte blocks is not a standard floppy size, using a derived geometry");
+        return false;
+    }
+
+    logmsg("---- Floppy format: ", format->name);
+    c = format->cylinders;
+    h = format->heads;
+    s = format->sectorsPerTrack;
+    return true;
+}
+
 static void autoConfigGeometry(image_config_t &img)
 {
     const char *method = "INI config";
@@ -410,12 +433,10 @@ static void autoConfigGeometry(image_config_t &img)
         uint8_t sect = 63;
         bool found_chs = false;
 
-        if (img.deviceType == S2S_CFG_FLOPPY_14MB && img.scsiSectors <= 2880)
+        if (find_floppy_geometry(img, cyl, head, sect))
         {
-            method = "device type floppy";
-            sect = 18;
-            head = 80;
             found_chs = true;
+            method = "floppy format";
         }
         else if (img.scsiSectors <= 1032192)
         {