95 lines
2.6 KiB
C
95 lines
2.6 KiB
C
/* Copyright 2021 Alain Knaff.
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* This file is part of mtools.
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*
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* Mtools is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Mtools is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Mtools. If not, see <http://www.gnu.org/licenses/>.
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*
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* "LBA Assist" geometry
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*/
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#include "sysincludes.h"
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#include "mtools.h"
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#include "lba.h"
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int compute_lba_geom_from_tot_sectors(struct device *dev)
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{
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unsigned int sect_per_track;
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uint32_t tracks;
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/* If already fully specified, nothing to do */
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if(dev->heads && dev->sectors && dev->tracks)
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return 0;
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/* If tot_sectors missing, return. Hopefully size still
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* specified somewhere that will be read at a later stage
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* (such as mformat command line) */
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if(dev->tot_sectors == 0) {
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return 0;
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}
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/* Floppy sizes, allowing for non-standard sizes with slightly
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more sectors per track than the default */
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if(dev->tot_sectors &&
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dev->tot_sectors <= 8640 && dev->tot_sectors % 40 == 0) {
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if(dev->tot_sectors <= 540) {
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/* double density 48tpi single sided */
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dev->tracks = 40;
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dev->heads = 1;
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} else if(dev->tot_sectors <= 1080) {
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/* double density 48tpi double sided or
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96 tpi single sided */
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if(dev->heads == 1)
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dev->tracks = 80;
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else {
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dev->tracks = 40;
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dev->heads = 2;
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}
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} else {
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/* double density 96tpi double sided,
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* high density, extra density */
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dev->tracks = 80;
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dev->heads = 2;
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}
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dev->sectors =
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(uint16_t)(dev->tot_sectors / dev->heads / dev->tracks);
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}
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/* Heads or sectors not known => fill them in both... */
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if(!dev->sectors || !dev->heads) {
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dev->sectors = 63;
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if (dev->tot_sectors < 16u*dev->sectors*1024)
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dev->heads = 16;
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else if (dev->tot_sectors < 32u*dev->sectors*1024)
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dev->heads = 32;
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else if (dev->tot_sectors < 64u*dev->sectors*1024)
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dev->heads = 64;
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else if (dev->tot_sectors < 128u*dev->sectors*1024)
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dev->heads = 128;
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else
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dev->heads = 255;
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}
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/* ... and calculate corresponding tracks */
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if(!dev->tracks) {
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sect_per_track = dev->heads * dev->sectors;
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tracks = (dev->tot_sectors + sect_per_track - 1) /
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sect_per_track;
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dev->tracks = tracks;
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}
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return 0;
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}
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