drm/udl: Move drm_dev_{enter, exit}() into udl_get_edid_block()

Protect the code in udl_get_edid_block() with drm_dev_enter() and
drm_dev_exit(), so that all callers automatically invoke it. The
function uses hardware resources, which can be hot-unplugged at
any time. The other code in udl_connector_detect() does not use the
resources of the hardware device and therefore does not require
protection.

This change will allow to use udl_get_edid_block() in various
contexts easily.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240510154841.11370-3-tzimmermann@suse.de

drivers/gpu/drm/udl/udl_modeset.c

@@ -434,13 +434,18 @@ static int udl_get_edid_block(void *data, u8 *buf, unsigned int block, size_t le
 	struct drm_device *dev = &udl->drm;
 	struct usb_device *udev = udl_to_usb_device(udl);
 	u8 *read_buff;
-	int ret;
+	int idx, ret;
 	size_t i;
 
 	read_buff = kmalloc(2, GFP_KERNEL);
 	if (!read_buff)
 		return -ENOMEM;
 
+	if (!drm_dev_enter(dev, &idx)) {
+		ret = -ENODEV;
+		goto err_kfree;
+	}
+
 	for (i = 0; i < len; i++) {
 		int bval = (i + block * EDID_LENGTH) << 8;
 
@@ -449,20 +454,23 @@ static int udl_get_edid_block(void *data, u8 *buf, unsigned int block, size_t le
 				      0xA1, read_buff, 2, USB_CTRL_GET_TIMEOUT);
 		if (ret < 0) {
 			drm_err(dev, "Read EDID byte %zu failed err %x\n", i, ret);
-			goto err_kfree;
+			goto err_drm_dev_exit;
 		} else if (ret < 1) {
 			ret = -EIO;
 			drm_err(dev, "Read EDID byte %zu failed\n", i);
-			goto err_kfree;
+			goto err_drm_dev_exit;
 		}
 
 		buf[i] = read_buff[1];
 	}
 
+	drm_dev_exit(idx);
 	kfree(read_buff);
 
 	return 0;
 
+err_drm_dev_exit:
+	drm_dev_exit(idx);
 err_kfree:
 	kfree(read_buff);
 	return ret;
@@ -474,21 +482,15 @@ static enum drm_connector_status udl_connector_detect(struct drm_connector *conn
 	struct udl_device *udl = to_udl(dev);
 	struct udl_connector *udl_connector = to_udl_connector(connector);
 	enum drm_connector_status status = connector_status_disconnected;
-	int idx;
 
 	/* cleanup previous EDID */
 	kfree(udl_connector->edid);
 	udl_connector->edid = NULL;
 
-	if (!drm_dev_enter(dev, &idx))
-		return connector_status_disconnected;
-
 	udl_connector->edid = drm_do_get_edid(connector, udl_get_edid_block, udl);
 	if (udl_connector->edid)
 		status = connector_status_connected;
 
-	drm_dev_exit(idx);
-
 	return status;
 }