drm/arm/hdlcd: use drmm_* to allocate driver structures

Use drm managed resources to allocate driver structures and get rid of
the deprecated drm_dev_alloc() call and replace it with
devm_drm_dev_alloc().

This also serves as preparation to get rid of drm_device->dev_private
and to fix use-after-free issues on driver unload.
Signed-off-by: Danilo Krummrich <dakr@redhat.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221026153431.72033-2-dakr@redhat.com

drivers/gpu/drm/arm/hdlcd_drv.c

@@ -247,13 +247,11 @@ static int hdlcd_drm_bind(struct device *dev)
 	struct hdlcd_drm_private *hdlcd;
 	int ret;
 
-	hdlcd = devm_kzalloc(dev, sizeof(*hdlcd), GFP_KERNEL);
-	if (!hdlcd)
-		return -ENOMEM;
+	hdlcd = devm_drm_dev_alloc(dev, &hdlcd_driver, typeof(*hdlcd), base);
+	if (IS_ERR(hdlcd))
+		return PTR_ERR(hdlcd);
 
-	drm = drm_dev_alloc(&hdlcd_driver, dev);
-	if (IS_ERR(drm))
-		return PTR_ERR(drm);
+	drm = &hdlcd->base;
 
 	drm->dev_private = hdlcd;
 	dev_set_drvdata(dev, drm);
@@ -319,7 +317,6 @@ static int hdlcd_drm_bind(struct device *dev)
 err_free:
 	drm_mode_config_cleanup(drm);
 	dev_set_drvdata(dev, NULL);
-	drm_dev_put(drm);
 
 	return ret;
 }
@@ -344,7 +341,6 @@ static void hdlcd_drm_unbind(struct device *dev)
 	drm_mode_config_cleanup(drm);
 	drm->dev_private = NULL;
 	dev_set_drvdata(dev, NULL);
-	drm_dev_put(drm);
 }
 
 static const struct component_master_ops hdlcd_master_ops = {

drivers/gpu/drm/arm/hdlcd_drv.h

@@ -7,6 +7,7 @@
 #define __HDLCD_DRV_H__
 
 struct hdlcd_drm_private {
+	struct drm_device		base;
 	void __iomem			*mmio;
 	struct clk			*clk;
 	struct drm_crtc			crtc;