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Date: Thu, 26 Jan 2006 20:28:32 +0100
From: Diego Calleja <diegocg@gmail.com>
To: Olivier Galibert <galibert@pobox.com>
Cc: vojtech@suse.cz, linux-kernel@vger.kernel.org
Subject: Re: CD writing in future Linux (stirring up a hornets' nest)
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El Thu, 26 Jan 2006 19:28:18 +0100,
Olivier Galibert <galibert@pobox.com> escribi?:

> - find the devices, what should I scan/filter on.  udev seems likes it
>   needs to run a program (/sbin/cdrom_id) or scan
>   /proc/sys/dev/cdrom/info just to know if a device is a cdrom...

Not at all - /sys/devices/pci0000:00/0000:00:0f.1/ide1/1.0/media 
tells that in my box. cdrom_id is, AFAICS, a way to find the
capabilities of the drive (ie, look if it's a cdrom or a dvd, etc)

You can get the info even with a fancy output:

root@estel# systool -v -b ide
Bus = "ide"

  Device = "0.0"
  Device path = "/sys/devices/pci0000:00/0000:00:0f.1/ide0/0.0"
    drivename           = "hda"
    media               = "disk"
    modalias            = "ide:m-disk"
    uevent              = <store method only>

  Device = "1.0"
  Device path = "/sys/devices/pci0000:00/0000:00:0f.1/ide1/1.0"
    drivename           = "hdc"
    media               = "cdrom"
    modalias            = "ide:m-cdrom"
    uevent              = <store method only>

I guess the cdrom driver could in the future be taught to export
more data (the previus cdrom drive is really a dvd drive...) to 
the sysfs interface to know if it's a dvd so that cdrom_id is 
unnecesary in some cases.



> - find the /dev name associated to a sysfs-found device.

HAL tells you that the sysfs path associated to a device.

root@estel # hal-get-property --udi '/org/freedesktop/Hal/devices/block_HL-DT-ST DVDRAM GSA-4163B-K01544H0250' --key 'block.device'
/dev/cd-rw
root@estel #

(yes, that "udi" path sucks)


> /dev/cdrw*, /dev/dvd*, /dev/dvdrw*.  Fedora core 3 creates
> /dev/cdrom*, /dev/cdwriter*, /dev/dvd*, /dev/dvdwriter*.  I guess from
> your email that SuSE does /dev/cdrecorder*.  And I'm not able to
> guess what fedora core 5, mandrake, debian, slackware and infinite
> number of derivatives do.

Although that sucks, IMO the whole point of udev/hal & friends is to
be able to make programs work regardless of what the name of the device
is (or at least, if I had to use a program, I would like that the program
design is good enought that it just ask the system what cd recorders are
connected to the system).
-
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