Commit e0f32f78 authored Sep 17, 2019 by Daniel Vetter

drm/kms: Duct-tape for mode object lifetime checks



commit 4f5368b5
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Fri Jun 14 08:17:23 2019 +0200

    drm/kms: Catch mode_object lifetime errors

uncovered a bit a mess in dp drivers. Most drivers (from a quick look,
all except i915) register all the dp stuff in their init code, which
is too early. With CONFIG_DRM_DP_AUX_CHARDEV this will blow up,
because drm_dp_aux_register tries to add a child to a device in sysfs
(the connector) which doesn't even exist yet.

No one seems to have cared thus far. But with the above change I also
moved the setting of dev->registered after the ->load callback, in an
attempt to keep old drivers from hitting any WARN_ON backtraces. But
that moved radeon.ko from the "working, by accident" to "now also
broken" category.

Since this is a huge mess I figured a revert would be simplest. But
this check has already caught issues in i915:

commit 1b9bd096
Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date:   Tue Aug 20 19:16:57 2019 +0300

    drm/i915: Do not create a new max_bpc prop for MST connectors

Hence I'd like to retain it. Fix the radeon regression by moving the
setting of dev->registered back to were it was, and stop the
backtraces with an explicit check for dev->driver->load.

Everyone else will stay as broken with CONFIG_DRM_DP_AUX_CHARDEV. The
next patch will improve the kerneldoc and add a todo entry for this.

Fixes: 4f5368b5 ("drm/kms: Catch mode_object lifetime errors")
Cc: Sean Paul <sean@poorly.run>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reported-by: Michel Dänzer <michel@daenzer.net>
Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Tested-by: Michel Dänzer <mdaenzer@redhat.com>
Cc: Michel Dänzer <michel@daenzer.net>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190917120936.7501-1-daniel.vetter@ffwll.ch

parent 2472518e

drivers/gpu/drm/drm_drv.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -976,14 +976,14 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
		if (ret)
		goto err_minors;

		dev->registered = true;

		if (dev->driver->load) {
		ret = dev->driver->load(dev, flags);
		if (ret)
		goto err_minors;
		}

		dev->registered = true;

		if (drm_core_check_feature(dev, DRIVER_MODESET))
		drm_modeset_register_all(dev);

drivers/gpu/drm/drm_mode_object.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -42,7 +42,7 @@ int __drm_mode_object_add(struct drm_device dev, struct drm_mode_object obj,
		{
		int ret;

		WARN_ON(dev->registered && !obj_free_cb);
		WARN_ON(!dev->driver->load && dev->registered && !obj_free_cb);

		mutex_lock(&dev->mode_config.idr_mutex);
		ret = idr_alloc(&dev->mode_config.object_idr, register_obj ? obj : NULL,
		@@ -104,7 +104,7 @@ void drm_mode_object_register(struct drm_device *dev,
		void drm_mode_object_unregister(struct drm_device *dev,
		struct drm_mode_object *object)
		{
		WARN_ON(dev->registered && !object->free_cb);
		WARN_ON(!dev->driver->load && dev->registered && !object->free_cb);

		mutex_lock(&dev->mode_config.idr_mutex);
		if (object->id) {

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