On Mon, Sep 23, 2024 at 09:28:23AM +0530, Raag Jadav wrote:
> Introduce device wedged event, which will notify userspace of wedged
> (hanged/unusable) state of the DRM device through a uevent. This is
> useful especially in cases where the device is no longer operating as
> expected and has become unrecoverable from driver context.
>
> Purpose of this implementation is to provide drivers a way to recover
> through userspace intervention. Different drivers may have different
> ideas of a "wedged device" depending on their hardware implementation,
> and hence the vendor agnostic nature of the event. It is up to the drivers
> to decide when they see the need for recovery and how they want to recover
> from the available methods.
>
> Current implementation defines three recovery methods, out of which,
> drivers can choose to support any one or multiple of them. Preferred
> recovery method will be sent in the uevent environment as WEDGED=<method>.
> Userspace consumers (sysadmin) can define udev rules to parse this event
> and take respective action to recover the device.
>
> Method | Consumer expectations
> -----------|-----------------------------------
> rebind | unbind + rebind driver
> bus-reset | unbind + reset bus device + rebind
> reboot | reboot system
> v4: s/drm_dev_wedged/drm_dev_wedged_event
> Use drm_info() (Jani)
> Kernel doc adjustment (Aravind)
> v5: Send recovery method with uevent (Lina)
> v6: Access wedge_recovery_opts[] using helper function (Jani)
> Use snprintf() (Jani)
Hmm... Isn't changelog in the cover letter is not enough?
...
> +/*
> + * Available recovery methods for wedged device. To be sent along with device
> + * wedged uevent.
> + */
> +#define WEDGE_LEN 32 /* Need 16+ */
This "Need 16+" comment seems unfinished as it doesn't tell why.
...
> +int drm_dev_wedged_event(struct drm_device *dev, enum wedge_recovery_method method)
> +{
> + char event_string[WEDGE_LEN] = {};
> + char *envp[] = { event_string, NULL };
> +
> + if (!test_bit(method, &dev->wedge_recovery)) {
> + drm_err(dev, "device wedged, recovery method not supported\n");
> + return -EOPNOTSUPP;
> + }
> + snprintf(event_string, sizeof(event_string), "WEDGED=%s", recovery_method_name(method));
Is sprintf.h being included already?
> + drm_info(dev, "device wedged, generating uevent\n");
> + return kobject_uevent_env(&dev->primary->kdev->kobj, KOBJ_CHANGE, envp);
> +}
...
> +/**
> + * enum wedge_recovery_method - Recovery method for wedged device in order
> + * of severity. To be set as bit fields in drm_device.wedge_recovery variable.
> + * Drivers can choose to support any one or multiple of them depending on their
> + * needs.
> + */
> +
Redundant blank line.
> +enum wedge_recovery_method {
> + /** @DRM_WEDGE_RECOVERY_REBIND: unbind + rebind driver */
> + DRM_WEDGE_RECOVERY_REBIND,
> +
> + /** @DRM_WEDGE_RECOVERY_BUS_RESET: unbind + reset bus device + rebind */
> + DRM_WEDGE_RECOVERY_BUS_RESET,
> +
> + /** @DRM_WEDGE_RECOVERY_REBOOT: reboot system */
> + DRM_WEDGE_RECOVERY_REBOOT,
> +
> + /** @DRM_WEDGE_RECOVERY_MAX: for bounds checking, do not use */
> + DRM_WEDGE_RECOVERY_MAX
> +};
...
> +extern const char *const wedge_recovery_opts[];
It's not NULL terminated. How users will know that they have an index valid?
Either you NULL-terminate that, or export the size as well (personally I would
go with the first approach).
...
> +static inline bool recovery_method_is_valid(enum wedge_recovery_method method)
> +{
> + if (method >= DRM_WEDGE_RECOVERY_REBIND && method < DRM_WEDGE_RECOVERY_MAX)
> + return true;
> +
> + return false;
Besides that this can be written as
return method >= DRM_WEDGE_RECOVERY_REBIND && method < DRM_WEDGE_RECOVERY_MAX;
> +}
this seems a runtime approach for what we have at compile-time, i.e. static_assert()
It's also possible to have as a third approach, but it's less robust.
--
With Best Regards,
Andy Shevchenko
