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    SubjectRe: [PATCH] libata: Don't trust current capacity values in identify words 57-58
    Robert Hancock wrote:
    > Hanno Böck reported a problem where an old Conner CP30254 240MB hard drive
    > was reported as 1.1TB in capacity by libata:
    > This was caused by libata trusting the drive's reported current capacity in
    > sectors in identify words 57 and 58 if the drive does not support LBA and the
    > current CHS translation values appear valid. Unfortunately it seems older
    > ATA specs were vague about what this field should contain and a number of drives
    > used values with wrong byte order or that were totally bogus. There's no
    > unique information that it conveys and so we can just calculate the number
    > of sectors from the reported current CHS values.
    > Signed-off-by: Robert Hancock <>
    > } else {
    > if (ata_id_current_chs_valid(id))
    > - return ata_id_u32(id, 57);
    > + return id[54] * id[55] * id[56];
    > else
    > return id[1] * id[3] * id[6];

    NAK. That's not quite correct, either.

    The LBA capacity can be larger than the CHS capacity,
    so we have to use the reported LBA values if at all possible.

    That's why ata_id_is_lba_capacity_ok() exists,
    and why it looks so peculiar.

    Some of those early drives really did require that kind of logic.


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