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Re: [nslu2-linux] CD/DVD-Rom Woes

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  • Mike (mwester)
    ... Probably because the rules to autoload those modules aren t present in the udev configuration files. You might try just adding the modules to /etc/modules,
    Message 1 of 7 , Apr 24, 2009
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      Charles Lindsey wrote:
      > I have just acquired a SONY DVD+-RW DW-D56A PDS8 (that is a well-known SONY OEM CD/DVD reader/writer intended for laptops) packaged as a USB standalone by some unidentified backstreet in China. It sort of works, but there are a few oddities that I have noticed which you people may be able to help with.
      >
      > I am using SlugosBE 4.8
      >
      > Following the Wiki, I downloaded the kernel modules cdrom, sr-mod and isofs and modprobed them (well, it seems you have to run depmod first).
      >
      > Question #1:
      > Whenever I reboot, it seems these modules are no longer installed (though modprobe -l claims that they are). I have to repeat the modprobes (well, at least for cdrom and sr-mod) before it will work. After that, dmesg shows that it has created /dev/sr0 - aka /dev/scd0.
      > So why is that, and how can I avoid it?

      Probably because the rules to autoload those modules aren't present in
      the udev configuration files.

      You might try just adding the modules to /etc/modules, and see if that's
      sufficient to have them autoloaded at each boot (the alternative would
      be to spend some time with the udev rules and see what's missing -- or,
      since the udev in SlugOS 4.8-beta is rather old, you might try SlugOS
      5.3-beta and see if that udev knows about your drive and the modules).

      > Question #2:
      > At first, when I tried to mount an inserted disc, it tried to tell me that No Media was present. But after that first reboot (plus modprobes) it appeared willing to recognise CDs and DVDs and divulge their contents correctly. Any suggestions as to why the reboot suddenly made it work?

      No idea; but my inclination would be again to look at udev -- and module
      load ordering.

      > Question #3:
      > It seems a little picky as to what CDs it will recognise, and is especially dubious of home-burnt ones (but my main host is dubious about the same CDs, so it is probably faded burning).
      > The drive is powered down the DVD line. This reduces the voltage available to 4.7 volts, but I presume that should normally be sufficient (certtainly the Slug itself seems happy to run at that voltage). So is that a reasonable expectation?
      > I tried adding a ittle extra power, and there was slight, but not repeatable, evidence that it found it easier to read some discs.

      Do not rely on the NSLU2 to be able to provide power to external
      devices. Especially ones with motors inside.

      > Question #4:
      > Is there some way to make the 'udev' system recognise when a new disc has been inserted and to mount it automatically? Udev recognises when the drive is plugged in, and might well be persuaded to mount it then. But nothing happens when a disc is inserted to the already-recognised drive.

      No. Udev doesn't do that; you'll find that on your desktop system there
      is a process, usually part of your windowing system, that polls the CD
      to see if a disc has been inserted. You would have to write such a
      process yourself.

      > Question #5:
      > Is there any 'eject' utility available? Not in the busybox apparently, and I do not know whether the drive would respond even if there was (though it does seem to know not to allow manual ejection of a disc that is still mounted).

      If its not on the ipkg search utility, then you'd have to compile it
      yourself. No reason for it not to work, just not something that's been
      asked for previously.

      > Question #6:
      > It is happy to mount DVDs, but there is one particular DVD which, when mounted, responds to 'ls' with
      > ls | cat
      >
      > äåää¤ä¼å¼åå
      > åæææå¼ä´æâ¸çç ç
      > åçæççä´ææ
      > åçæççä´ææâ¸çæç
      > åä¤äää¼å¼åå
      > å ççæç
      > æççæ¼ççæ¸â¸æ¤æ¸æ
      > ææçæ
      > ççæççâ¸ææ´ç
      > ççæççâ¸æç æ
      >
      > but 'od' shows that there are lots of unprintable characters hidden in there.
      >
      > ls | od -c {and then edit it into neat lines}
      >
      > 344 204 200 345 224 200 344 220 200 344 244 200 344 274 200
      > 345 274 200 345 220 200 345 214 200 \n
      > 345 210 200 346 224 200 346 204 200 346 220 200 345 274 200
      > 344 264 200 346 224 200 342 270 200 347 220 200 347 240 200
      > 347 220 200 \n
      > 345 214 200 347 220 200 346 204 200 347 210 200 347 220 200
      > 344 264 200 346 204 200 346 214 200 \n
      > 345 214 200 347 220 200 346 204 200 347 210 200 347 220 200
      > 344 264 200 346 204 200 346 214 200 342 270 200 347 200 200
      > 346 214 200 347 220 200 \n
      > 345 230 200 344 244 200 344 220 200 344 224 200 344 274 200
      > 345 274 200 345 220 200 345 214 200 \n
      > 345 240 200 347 220 200 347 210 200 346 204 200 347 214 200
      > \n
      > 346 204 200 347 224 200 347 220 200 346 274 200 347 210 200
      > 347 224 200 346 270 200 342 270 200 346 244 200 346 270 200
      > 346 230 200 \n
      > 346 220 200 346 204 200 347 220 200 346 204 200 \n
      > 347 214 200 347 220 200 346 204 200 347 210 200 347 220 200
      > 342 270 200 346 210 200 346 264 200 347 200 200 \n
      > 347 214 200 347 220 200 346 204 200 347 210 200 347 220 200
      > 342 270 200 346 224 200 347 240 200 346 224 200 \n
      >
      > and that seems to suggest that the filenames are encoded as 3 bytes per character, with the 3rd byte always 0200. It does not appear to be UTF-8, so any suggestions? All the directories on the disc are like that, although the files themselves, when you can find them, are all as you would expect.

      Try installing some other character sets/locales - UTF16 at least.

      > Question #7:
      > Now to try burning DVDs! Am I correct in assuming that there is no precompiled cdr-tools for SlugosBE, and that I have to compile that package myself? I have got as far as dowloading the soure for cdrtools 2.01.01a56, but it looks like a fairly hard slog to cross-compile it all :-(.

      Again, if its not on the ipkg search engine you'd have to build it
      yourself. Frankly, I think you will be disappointed; I don't think the
      NSLU2 can keep up with any reasonable speed burner. Search the mailing
      list archives; this was discussed some time ago, and IIRC one must use
      one of - or + R DVDs in order to ensure that under-runs don't result in
      burning coasters (but I don't recall which of the +/- signs you need).

      Mike (mwester)
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