Thank you very much!
On 2015-06-25 02:04, Jude Nelson wrote:
Hey everyone,
After a longer-than-expected development cycle, I have the latest news
for vdev.
The TL;DR is that vdev has gained enough infrastructure to generate
the information that normally gets put in /run/udev. This is
important for most libudev clients, because this information gets used
to detect and enumerate hardware. It's the way the X server detects
input devices via udev, for example.
This is still being heavily tested, and is not complete, but I am
please to report that:
* vdev now tracks device properties and device tags, under
/dev/metadata/$DEVPATH/properties and /dev/metadata/$DEVPATH/tags/,
respectively. They are added by shell library subroutines available
to vdev's helpers (in subr.sh).
* vdev now uses the same hardware database as udev to report
human-curated hardware properties (such as human-readable vendor
strings). To keep things simple, vdev comes with a script that
generates a squashfs filesystem image from the *.hwdb files installed
to /lib/udev/hwdb.d and /etc/udev/hwdb.d. This is our alternative to
systemd's/udevd's mmap()-able on-disk hwdb trie. The filesystem image
itself gets mounted to /dev/metadata/hwdb by the pre-seed script, and
vdev now comes with a helper tool (hwdb.sh) that can use a combination
of a modalias string, a devpath, a subsystem path, and some sysfs
information to look up the device properties.
* vdev now comes with a "udev-compat.sh" helper script that reads
vdev's /dev/metadata/ directory and hardware database in order to
generate /dev/metadata/udev, which is meant to be symlinked to
/run/udev. This lets the udev_enumerate API detect and enumerate
devices by tags and properties. It is important to emphasize that
this helper is logically isolated from the rest of vdev--vdev gets
along just fine without it (since all udev-isms are contained by this
helper), so if you don't need /run/udev, you can safely disable this
helper script.
* Disk property detection has been significantly improved, and is much
closer to how udev does it (including adding support for querying a
disk's parent device's properties, which is necessary to handle
partitions properly). Thanks to Didier for working with me on this!
In time, it will also work the busybox tools, but I am still working
on getting busybox's blkid to work here (specifically, we need the
"-p" flag to work in order to get low-level partition table
information and filesystem metadata).
There is of course more work to be done on this, but the next big
milestone (my next goal) will be to boot to X with vdevd, without
having to generate an xorg.conf. I have not tried this yet, and I do
not expect it to work as of the latest commit, but I believe that all
the necessary infrastructure is in place to begin the painstaking
process of ensuring that vdev detects enough of the host's devices'
properties for commonly-used libudev clients work as they did with
udev. This will confirm that we generate enough of /run/udev/ for
alpha.
Thanks,
Jude
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