Bjorn Andersson
23688db35a
The nbdkit plugin is undiscoverable without documentation. Describe how to build it with meson (including the nbdkit development dependency) and walk through serving a LUN end to end: starting nbdkit, confirming the export with nbdinfo, attaching it to /dev/nbdN with nbd-client, and reading it, plus a warning that writes go straight to the device's flash. The walkthrough lives in docs/nbd.md to keep the ever growing README lean; the README gets a short section pointing to it, and the markdown-lint wrapper now lints everything under docs/ so future documents are covered automatically. Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org> Signed-off-by: Igor Opaniuk <igor.opaniuk@oss.qualcomm.com>
2.8 KiB
nbdkit plugin
In addition to the qdl programmer, an
nbdkit plugin can be built. It uploads
the firehose programmer and exposes a physical partition (LUN) as a block
device on the host, so its partition table can be edited and its partitions
mounted with ordinary tools.
Building the plugin
The plugin is built by meson only when the nbdkit development files are
present. Install the runtime and the development package, then reconfigure:
- Debian/Ubuntu:
sudo apt install nbdkit nbdkit-dev - Fedora:
sudo dnf install nbdkit nbdkit-devel
meson setup --reconfigure build
meson compile -C build
meson setup reports Run-time dependency nbdkit found: YES and produces
build/nbdkit-qdl-plugin.so. Pass -Dnbdkit=enabled to make the plugin
mandatory (the build fails if nbdkit is missing) instead of the default
auto-detection.
Plugin parameters
programmer- firehose programmer to upload (required)lun- physical partition (LUN) to expose, defaults to1storage-ufsoremmc, selects the firehose configurationdebug- set to1for verbose qdl logging
Serving a LUN as a block device
The device must be in EDL mode, exactly as for a normal qdl run.
1. Start nbdkit. In one terminal, launch the server. -f keeps it in the
foreground and -v prints a debug log:
sudo nbdkit -fv ./build/nbdkit-qdl-plugin.so \
programmer=prog_firehose_ddr.elf lun=0
nbdkit now listens on TCP port 10809 (nbd://localhost). It does not touch
the device yet: the programmer is uploaded and firehose is configured lazily,
the first time a client connects, and kept configured until nbdkit exits.
2. Confirm the export. In a second terminal, query it. This triggers the one-time device setup and prints the LUN's size, so it is the quickest check that the plugin can talk to the board:
nbdinfo nbd://localhost
3. Attach a kernel block device. Load the nbd module and bind the export
to a /dev/nbdN node with nbd-client. -N default selects the plugin's
default export, 10809 is the port:
sudo modprobe nbd
sudo nbd-client -N default localhost 10809 /dev/nbd0
/dev/nbd0 now mirrors the LUN. nbd-client prints the negotiated size on
connect.
4. Read the LUN. Query its size (in bytes) and read from it with any standard tool:
sudo blockdev --getsize64 /dev/nbd0
sudo dd if=/dev/nbd0 of=/tmp/lun0.head bs=1M count=1
You can partition, mount, dd, or image /dev/nbd0 like any other disk.
5. Detach when done, then stop nbdkit (Ctrl-C in its terminal):
sudo nbd-client -d /dev/nbd0
Warning
Writing to
/dev/nbd0writes straight to the device's flash. Firehose reads are also slow - every request is a separate firehose command - so large transfers take a while; a bigger block size (bs=8M) helps.