gpu: host1x: Do not link logical devices to DT nodes

Logical devices created by the host1x bus infrastructure don't need to
be associated with a device tree node. Doing so will cause the driver
core to attempt to hook up IOMMU operations and fail because it is not
a real device.

However, for backwards-compatibility, we need to provide various OF_*
uevent variables that were previously provided by of_device_uevent() and
which are parsed by libdrm in userspace when querying the available
devices. Do this by implementing a uevent callback for the host1x bus.

Signed-off-by: Thierry Reding <[e-mail]>

drivers/gpu/host1x/bus.c

···
 	return strcmp(dev_name(dev), drv->name) == 0;
 }
 
+static int host1x_device_uevent(struct device *dev,
+				struct kobj_uevent_env *env)
+{
+	struct device_node *np = dev->parent->of_node;
+	unsigned int count = 0;
+	struct property *p;
+	const char *compat;
+
+	/*
+	 * This duplicates most of of_device_uevent(), but the latter cannot
+	 * be called from modules and operates on dev->of_node, which is not
+	 * available in this case.
+	 *
+	 * Note that this is really only needed for backwards compatibility
+	 * with libdrm, which parses this information from sysfs and will
+	 * fail if it can't find the OF_FULLNAME, specifically.
+	 */
+	add_uevent_var(env, "OF_NAME=%pOFn", np);
+	add_uevent_var(env, "OF_FULLNAME=%pOF", np);
+
+	of_property_for_each_string(np, "compatible", p, compat) {
+		add_uevent_var(env, "OF_COMPATIBLE_%u=%s", count, compat);
+		count++;
+	}
+
+	add_uevent_var(env, "OF_COMPATIBLE_N=%u", count);
+
+	return 0;
+}
+
 static int host1x_dma_configure(struct device *dev)
 {
 	return of_dma_configure(dev, dev->of_node, true);
···
 struct bus_type host1x_bus_type = {
 	.name = "host1x",
 	.match = host1x_device_match,
+	.uevent = host1x_device_uevent,
 	.dma_configure = host1x_dma_configure,
 	.pm = &host1x_device_pm_ops,
 };
···
 	device->dev.dma_mask = &device->dev.coherent_dma_mask;
 	dev_set_name(&device->dev, "%s", driver->driver.name);
 	device->dev.release = host1x_device_release;
-	device->dev.of_node = host1x->dev->of_node;
 	device->dev.bus = &host1x_bus_type;
 	device->dev.parent = host1x->dev;