On Sun, Feb 03, 2019 at 04:41:56PM +0100, Noralf Trønnes wrote:
> The only thing now that makes drm_dev_unplug() special is that it sets
> drm_device->unplugged. Move this code to drm_dev_unregister() so that we
> can remove drm_dev_unplug().
>
> Signed-off-by: Noralf Trønnes <noralf@xxxxxxxxxxx>
> ---
>
> Maybe s/unplugged/unregistered/ ?
>
> I looked at drm_device->registered, but using that would mean that
> drm_dev_is_unplugged() would return before drm_device is registered.
> And given that its current purpose is to prevent race against connector
> registration, I stayed away from it.
Makes sense. I think having unregistered along with registered might cause some
confusion unless it's really clearly documented. Perhaps
s/unplugged/unregistered/ and s/registered/initialized/ but init has its own
meaning...
I'd hate to hold up the patchset over naming bikeshed, so maybe this would be
better off as a follow-on series where everyone can pile on opinions. So,
Reviewed-by: Sean Paul <sean@xxxxxxxxxx>
>
> Noralf.
>
>
> drivers/gpu/drm/drm_drv.c | 27 +++++++++++++++------------
> include/drm/drm_drv.h | 10 ++++------
> 2 files changed, 19 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 05bbc2b622fc..e0941200edc6 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -366,15 +366,6 @@ EXPORT_SYMBOL(drm_dev_exit);
> */
> void drm_dev_unplug(struct drm_device *dev)
> {
> - /*
> - * After synchronizing any critical read section is guaranteed to see
> - * the new value of ->unplugged, and any critical section which might
> - * still have seen the old value of ->unplugged is guaranteed to have
> - * finished.
> - */
> - dev->unplugged = true;
> - synchronize_srcu(&drm_unplug_srcu);
> -
> drm_dev_unregister(dev);
> drm_dev_put(dev);
> }
> @@ -832,11 +823,14 @@ EXPORT_SYMBOL(drm_dev_register);
> * drm_dev_register() but does not deallocate the device. The caller must call
> * drm_dev_put() to drop their final reference.
> *
> - * A special form of unregistering for hotpluggable devices is drm_dev_unplug(),
> - * which can be called while there are still open users of @dev.
> + * This function can be called while there are still open users of @dev as long
> + * as the driver protects its device resources using drm_dev_enter() and
> + * drm_dev_exit().
> *
> * This should be called first in the device teardown code to make sure
> - * userspace can't access the device instance any more.
> + * userspace can't access the device instance any more. Drivers that support
> + * device unplug will probably want to call drm_atomic_helper_shutdown() first
> + * in order to disable the hardware on regular driver module unload.
> */
> void drm_dev_unregister(struct drm_device *dev)
> {
> @@ -845,6 +839,15 @@ void drm_dev_unregister(struct drm_device *dev)
> if (drm_core_check_feature(dev, DRIVER_LEGACY))
> drm_lastclose(dev);
>
> + /*
> + * After synchronizing any critical read section is guaranteed to see
> + * the new value of ->unplugged, and any critical section which might
> + * still have seen the old value of ->unplugged is guaranteed to have
> + * finished.
> + */
> + dev->unplugged = true;
> + synchronize_srcu(&drm_unplug_srcu);
> +
> dev->registered = false;
>
> drm_client_dev_unregister(dev);
> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> index ca46a45a9cce..c50696c82a42 100644
> --- a/include/drm/drm_drv.h
> +++ b/include/drm/drm_drv.h
> @@ -736,13 +736,11 @@ void drm_dev_unplug(struct drm_device *dev);
> * drm_dev_is_unplugged - is a DRM device unplugged
> * @dev: DRM device
> *
> - * This function can be called to check whether a hotpluggable is unplugged.
> - * Unplugging itself is singalled through drm_dev_unplug(). If a device is
> - * unplugged, these two functions guarantee that any store before calling
> - * drm_dev_unplug() is visible to callers of this function after it completes
> + * This function can be called to check whether @dev is unregistered. This can
> + * be used to detect that the underlying parent device is gone.
> *
> - * WARNING: This function fundamentally races against drm_dev_unplug(). It is
> - * recommended that drivers instead use the underlying drm_dev_enter() and
> + * WARNING: This function fundamentally races against drm_dev_unregister(). It
> + * is recommended that drivers instead use the underlying drm_dev_enter() and
> * drm_dev_exit() function pairs.
> */
> static inline bool drm_dev_is_unplugged(struct drm_device *dev)
> --
> 2.20.1
>
--
Sean Paul, Software Engineer, Google / Chromium OS
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