Messages in this thread | | | Date | Tue, 14 Feb 2006 19:59:25 +0100 | From | Olivier Galibert <> | Subject | Re: CD writing in future Linux (stirring up a hornets' nest) |
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On Mon, Feb 13, 2006 at 07:49:21AM -0800, Greg KH wrote: > On Mon, Feb 13, 2006 at 02:26:54PM +0100, Joerg Schilling wrote: > > Greg KH <greg@kroah.com> wrote: > > > > > On Fri, Feb 10, 2006 at 04:06:39PM -0500, Bill Davidsen wrote: > > > > > > > > The kernel could provide a list of devices by category. It doesn't have > > > > to name them, run scripts, give descriptions, or paint them blue. Just a > > > > list of all block devices, tapes, by major/minor and category (ie. > > > > block, optical, floppy) would give the application layer a chance to do > > > > it's own interpretation. > > > > > > It does so today in sysfs, that is what it is there for. > > > > Do you really whant libscg to open _every_ non-directory file under /sys? > > Of course not. Here's one line of bash that gets you the major:minor > file of every block device in the system: > block_devices="$(echo /sys/block/*/dev /sys/block/*/*/dev)"
Of course, that's entirely useless if you're not root.
So what you _really_ have to do is to call udevinfo -e. If that fails, call udevinfo -d, that's the old name for the option which got changed along the way. The result is blocks of text lines separated by blank lines, text lines of the form:
I: value
Where I is a one-letter uppercase identifier, and value a value.
If you get E: entries, you're lucky. All cdroms have a E: ID_CDROM=1 entry, but these entries appeared late. Otherwise, the best bet is to scan the S: entries for something matching /cdrom/. When you have a bloc of lines, get the N: entry, that's the node name, and prepend it with the result of udevinfo -r (usually /dev/, but that's not mandatory). That will give you the device node path to open (don't forget O_EXCL to avoid Hal stomping all over you), which you can then use SG_IO with.
If udevinfo is not available, you'll have to try opening all /dev/hd*, /dev/sr*, /dev/scd*, /dev/sg*, /dev/cdr* and /dev/dvd* (don't stop at the first -EANYTHING though, otherwise you'll miss some). Then you can poke the device carefully with SG_IO.
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