1 files changed, 94 insertions, 0 deletions
diff --git a/lba.c b/lba.c
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+++ b/lba.c
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+/*  Copyright 2021 Alain Knaff.
+ *  This file is part of mtools.
+ *
+ *  Mtools 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.
+ *
+ *  Mtools 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 Mtools.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * "LBA Assist" geometry
+ */
+
+#include "sysincludes.h"
+#include "mtools.h"
+#include "lba.h"
+
+int compute_lba_geom_from_tot_sectors(struct device *dev)
+{
+	unsigned int sect_per_track;
+	uint32_t tracks;
+
+	/* If already fully specified, nothing to do */
+	if(dev->heads && dev->sectors && dev->tracks)
+		return 0;
+
+	/* If tot_sectors missing, return. Hopefully size still
+	 * specified somewhere that will be read at a later stage
+	 * (such as mformat command line) */
+	if(dev->tot_sectors == 0) {
+		return 0;
+	}
+
+	/* Floppy sizes, allowing for non-standard sizes with slightly
+	   more sectors per track than the default */
+	if(dev->tot_sectors &&
+	   dev->tot_sectors <= 8640 && dev->tot_sectors % 40 == 0) {
+		if(dev->tot_sectors <= 540) {
+			/* double density 48tpi single sided */
+			dev->tracks = 40;
+			dev->heads = 1;
+		} else if(dev->tot_sectors <= 1080) {
+			/* double density 48tpi double sided or
+			   96 tpi single sided   */
+
+			if(dev->heads == 1)
+				dev->tracks = 80;
+			else {
+				dev->tracks = 40;
+				dev->heads = 2;
+			}
+		} else {
+			/* double density 96tpi double sided,
+			 * high density, extra density */
+			dev->tracks = 80;
+			dev->heads = 2;
+		}
+		dev->sectors =
+			(uint16_t)(dev->tot_sectors / dev->heads / dev->tracks);
+	}
+
+
+	/* Heads or sectors not known => fill them in both... */
+	if(!dev->sectors || !dev->heads) {
+		dev->sectors = 63;
+
+		if (dev->tot_sectors < 16u*dev->sectors*1024)
+			dev->heads = 16;
+		else if (dev->tot_sectors < 32u*dev->sectors*1024)
+			dev->heads = 32;
+		else if (dev->tot_sectors < 64u*dev->sectors*1024)
+			dev->heads = 64;
+		else if (dev->tot_sectors < 128u*dev->sectors*1024)
+			dev->heads = 128;
+		else
+			dev->heads = 255;
+	}
+
+	/* ... and calculate corresponding tracks */
+	if(!dev->tracks) {
+		sect_per_track = dev->heads * dev->sectors;
+		tracks = (dev->tot_sectors + sect_per_track - 1) /
+			sect_per_track;
+		dev->tracks = tracks;
+	}
+
+	return 0;
+}