Re: [gentoo-user] Udev confusion: Rules for a mp3 player

["Jc García" <jyo.garcia@gmail.com>]

2014-06-28 8:57 GMT-06:00  <meino.cramer@gmx.de>:
> Hi,
>
> For my mp3-player I want to write udev rules to give better names
> to the according entries under /dev
>
> Problem is: Th eplayer has an internal flash, which only holds the firmware
> (in my case) and a sd-card slot, in which you can insert a flash card
> with music files.
>
> The internal memory has a partition directly on - say - sdb and the
> sd-card in the slot is regulary formatted and represents itsself as
> sdc and sdc1.
>
> With udevadm I determined the serial number of the device (to make it
> unique) and the model ("Internal storage" and "SD card slot"), which
> seems to make it easy to buit rules from.
> The one and only reason for not being THAT happy is: The rules didn't work.
>
> Here:
> http://www.reactivated.net/writing_udev_rules.html
>
> I read some instructions.
> It is said that one should not combine elements of one device and more
> than one parent.
>
> Is "device" meant as "the entry under /dev" or is it to be understand
> as "the electric entity on my desktop (the player)".
>
> I want rules which also work, if another sdcard of a different size is
> inserted into the player...
>
> How can I write rules to map the internal storage, the whole device
> (aka /dev/sdc) of the sdcard (for example for reformatting reasons)
> and the partition of the sdcard (aka /dev/sdc1), which work?
>
> To this email I have attached the gzipped outputs of the according
> udevadm calls.
>
> Thank you very much for any help in advance!
> Best regards,
> mcc
>
> PS:
> This is what I have tried and which does *NOT* work!
> SUBSYSTEM=="block",ATTRS{model}=="Internal Storage",ATTRS{serial}=="1A8C518301403210B00000000",SYMLINK+="sansaclipzip_root"
> SUBSYSTEM=="block",ATTRS{model}=="SD Card Slot    ",ATTR{partition}=="1", ATTRS{serial}=="1A8C518301403210B00000000", SYMLINK+="sansaclipzip_data_1"
> SUBSYSTEM=="block",ATTRS{model}=="SD Card Slot    ",ATTRS{serial}=="1A8C518301403210B00000000", SYMLINK+="sansaclipzip_data"
>
>
I'm not going to help you with your udev rules, but just point out, it
seems to me you are going to a more complicated layer than you need
to, if you just want personalized naming for your partitions under
/dev (for using with scripts or something like that), I would suggest
you to use the label feature, of the filesystems you are going to use
for those blocks, this will cause udev to generate respective
/dev/disk/by-label/* symlinks, altought I guess if you already know
this if you are playing with udev rules.