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    SubjectRe: PROBLEM: Impossible to read files from a CD-Rom
    On Fri, 12 Sep 2003, Jens Axboe wrote:
    > On Mon, Sep 08 2003, Samuel Thibault wrote:
    >> On Mon 18 aug 2003 18:35:22 GMT, Sébastien Hinderer wrote:
    >> > I'm using a vanila linux-2.6.0-test3. When I try to use a CD-Rom,
    >> > the mount is successful, so are the calls to ls. However, as soon
    >> > as I try to read a file, I get a lot of messages such as :


    >> We dug a little bit this Monday with Sebastien, and found out some
    >> troubles: the call to set_capacity at the end of cdrom_read_toc()
    >> writes a strange value, which is not always the same, even for the
    >> same reinserted CD-ROM, seemingly because it came from
    >> cdrom_get_last_written():


    > I'd be more interested in fixing the real bug: why does your drive
    > return zero length, and only sporadically?

    This sounds somewhat like a problem I have playing DVD-R discs on one
    DVD drive (Pioneer slot-loader), using Xine and the RAW device.

    Basically, for some discs, the raw device cannot read any block, as the
    capacity of the disc is reported as zero blocks.

    I don't have trouble accessing the content on any other machine, though,
    and can access the files through a mounted filesystem.

    /proc/ide/hdc/capacity contains zero in these cases.

    Occasionally, for a disc that does this, I get a valid (looking) size,
    but not very often -- one time in twenty, at most.

    I am happy to work on debugging this, if there is anything that can be
    done to help identify the problem.

    This only seems to occur with DVD-R discs, and without any predictable


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    especially when it is deep.
    -- Felix Frankfurter
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