On 11/5/26 16:18, Petr Oros wrote:
Add dpllsim, a driver providing simulated DPLL devices for testing the
DPLL subsystem and its userspace tooling without real hardware, in the
same spirit as netdevsim for network devices. The DPLL core identifies
a device by clock ID, index and module only, so the driver needs no bus
and no struct device at all.
Instances are created and configured at runtime through configfs,
following the gpio-sim precedent for objects that userspace creates on
demand. Creating a directory under/sys/kernel/config/dpllsim/ allocates
an instance, its clock_id attribute selects the clock ID, writing 1 to
live registers the DPLL device with the core and writing 0 unregisters
it again. Removing the directory tears a live instance down implicitly.
Keeping registration separate from creation lets a test register and
unregister the same device repeatedly, which is where the core bugs the
driver is meant to catch tend to live, and it allows the structural
attributes to be refused with EBUSY while the device is visible to
userspace. Unlike sysfs, configfs does not imply a stable ABI, which
suits a driver whose knobs exist only to drive tests.
Reading live reports whether the device is registered with the DPLL
subsystem, it turns 1 only once the whole live transition succeeded and
0 again as the first step of the teardown. The configuration is frozen
earlier, from the moment the transition obtains the device handle, so
that a configuration write racing with the transition is refused rather
than lost.
The device registers as a PPS type DPLL with the two mandatory callbacks
only. mode_get reports automatic mode and lock_status_get reports
unlocked with no error. Pins come with the following patches and the
simulation of lock acquisition with a later series.
Document the configfs layout under Documentation/driver-api and add a
MAINTAINERS entry.
Signed-off-by: Petr Oros<redacted>
Reviewed-by: Ivan Vecera <ivecera@redhat.com>