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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org References: <20261105151852.1844305-1-poros@redhat.com> <20261105151852.1844305-2-poros@redhat.com> Content-Language: en-US From: Ivan Vecera In-Reply-To: <20261105151852.1844305-2-poros@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 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 Reviewed-by: Ivan Vecera