Re: Adieu, Fedora



On 06/14/2011 11:43 PM, Joe Zeff wrote:
On 06/14/2011 03:01 PM, Marcus D. Leech wrote:
Which of those four items do you think should "show up automatically"
when you plug in the drive?

All four seems reasonable. Again, however, your missing my main
complaint. It's not that the USB services don't report the label, it's
that the devs claim falsely that it does and refused to look at the
proof that they are wrong. Simply telling me "shut up and go away!"
isn't a rational response; it's more like an ostrich sticking its head
in the sand and hoping that the problem will go away.

If you mean the threads "Simple USB/Linux question" and "more on flash drives"
from a linux-usb a couple of years back I don't think I share your
interpretation of the responses you received.

http://kerneltrap.org/mailarchive/linux-usb/2009/12/26/6256324/thread
http://kerneltrap.org/mailarchive/linux-usb/2009/12/27/6256335/thread

The statement "the kernel drivers make all the data available to the window
manager, and it decides how to show the device." /includes/ data that is stored
"inside" the device (when it is a block device like a USB mass storage device).
This is also what was meant with the comment "It's probably pulling the
information directly from the device, or via udev.".

The kernel provides basic standardised hardware properties directly via the
sysfs virtual file system. This includes the attributes listed above (Vendor,
Product etc.) - in short, anything that shows up in the output of "udevadm info
-a" for a given piece of hardware.

In modern Linux distributions programs like udev and udisks call out to
lower-level userspace programs like scsi_id, blkid etc. to retrieve additional
information about what is stored on the device. These programs open the device
from userspace and read whatever information they need to via I/O calls, ioctl
commands etc.

This includes the filesystem-specific label, UUID and other metadata - Linux has
long had a policy of handling this type of data in userspace and for good
reasons (it's part of the UNIX heritage of separating mechanism from policy -
the kernel provides the mechanisms to access the information but applies no
particular policy as to what to do with it or how to present it).

Partition tables are one ugly exception to this but there have even been
discussions in recent years (and at least one patch set) to remove those from
the kernel and handle them in user space instead.

Reading, reporting and interpreting labels are not the job of the USB drivers or
their maintainers. The right people to help really are the maintainers of the
user space hardware abstraction subsystems and the various desktop environments.

Regards,
Bryn.

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