Do not set d_fwsectors nor d_fwheads. Primarily because the values
tend to be invalid. On a Beaglebone Black, we get 8192 sectors per track and that causes major breakages. Differential Revision: D2646 Reviewed by: ian@ imp@
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@ -163,33 +163,10 @@ mmcsd_attach(device_t dev)
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d->d_sectorsize = mmc_get_sector_size(dev);
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d->d_maxsize = mmc_get_max_data(dev) * d->d_sectorsize;
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d->d_mediasize = (off_t)mmc_get_media_size(dev) * d->d_sectorsize;
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d->d_stripeoffset = 0;
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d->d_stripesize = mmc_get_erase_sector(dev) * d->d_sectorsize;
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d->d_unit = device_get_unit(dev);
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d->d_flags = DISKFLAG_CANDELETE;
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d->d_delmaxsize = mmc_get_erase_sector(dev) * d->d_sectorsize * 1; /* conservative */
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/*
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* The d_fw* values are fake. However, layout is aided by making the
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* number of fwsectors equal to the erase sectors from the drive since
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* we set the stripe size equal to that. We set fwheads such that there
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* are ~20 cylinder groups since all values are somewhat arbitrary here
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* and this gives good behavior with ffs without wasting too much
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* space. Sadly, geom_part wants to round partitions to these
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* values. While not bad, in and of itself, the values we present here
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* will almost certainly be different then the values that USB SD
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* adapters use and there's too much variation between brands to just
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* use those values here. Also SD to ATA adapters favor traditional
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* ata sizes, which are different again from the USB adapters (which
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* favor SCSI values). This rounding leads to a loss of up to 5% of the
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* usable space (usually much less, but that's why 20 was selected: to
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* limit this effect at a few percent). gpart needs a way to override
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* this behavior for situations like this, but doesn't provide
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* one. Perhaps this behavior should be tunable as well, but maybe that
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* belongs in the disk layer. These values will be much better than
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* the default ones.
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*/
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d->d_fwsectors = mmc_get_erase_sector(dev);
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d->d_fwheads = mmc_get_media_size(dev) / (d->d_fwsectors * 20);
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d->d_delmaxsize = mmc_get_erase_sector(dev) * d->d_sectorsize;
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strlcpy(d->d_ident, mmc_get_card_sn_string(dev), sizeof(d->d_ident));
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strlcpy(d->d_descr, mmc_get_card_id_string(dev), sizeof(d->d_descr));
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