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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;
}
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