[PATCH v2] drm/panel: tdo-tl070wsh30: Remove panel on attach failure

[PATCH v2] drm/panel: tdo-tl070wsh30: Remove panel on attach failure

[Muhammad Bilal]

tdo_tl070wsh30_panel_add() calls drm_panel_add() to link the panel
into the global panel_list before tdo_tl070wsh30_panel_probe() calls
mipi_dsi_attach(). The panel object itself is allocated with
devm_drm_panel_alloc(), which only arranges for an automatic
drm_panel_put() (via devm_add_action_or_reset()) when the DSI device
is torn down; unlike devm_drm_panel_add(), it does not call
drm_panel_remove() for you.

If mipi_dsi_attach() fails, probe() returns the error directly:

        return mipi_dsi_attach(dsi);

Once probe() returns an error, the driver core releases devres
resources for the device, which drops the allocation's own
reference. But drm_panel_add() had already taken its own reference
and linked panel->list into the global panel_list, and nothing
undoes that. The panel is left registered in panel_list pointing at
a device that failed to bind, where it can still be found and
dereferenced by later lookups/iterations such as
of_drm_find_panel() or find_panel_by_fwnode().

Switch to devm_mipi_dsi_attach() so mipi_dsi_detach() is handled
automatically on unbind and tdo_tl070wsh30_panel_remove() no longer
needs the manual call. It still returns directly on failure without
touching panel_list, so drm_panel_remove() stays on that path.

Fixes: cf40c6600592 ("drm: panel: add TDO tl070wsh30 panel driver")
Cc: stable@vger.kernel.org
Suggested-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
---
Changes in v2:
- Switch to devm_mipi_dsi_attach(), as suggested by Neil. Drop the
  now-redundant mipi_dsi_detach() call from remove().
- Keep drm_panel_remove() on the attach failure path, since
  devm_mipi_dsi_attach() doesn't touch panel_list on its own.

 drivers/gpu/drm/panel/panel-tdo-tl070wsh30.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-tdo-tl070wsh30.c b/drivers/gpu/drm/panel/panel-tdo-tl070wsh30.c
index fa961abdd2d7..ea59d4993ff5 100644
--- a/drivers/gpu/drm/panel/panel-tdo-tl070wsh30.c
+++ b/drivers/gpu/drm/panel/panel-tdo-tl070wsh30.c
@@ -179,17 +179,16 @@ static int tdo_tl070wsh30_panel_probe(struct mipi_dsi_device *dsi)
 	if (err < 0)
 		return err;
 
-	return mipi_dsi_attach(dsi);
+	err = devm_mipi_dsi_attach(&dsi->dev, dsi);
+	if (err < 0)
+		drm_panel_remove(&tdo_tl070wsh30->base);
+
+	return err;
 }
 
 static void tdo_tl070wsh30_panel_remove(struct mipi_dsi_device *dsi)
 {
 	struct tdo_tl070wsh30_panel *tdo_tl070wsh30 = mipi_dsi_get_drvdata(dsi);
-	int err;
-
-	err = mipi_dsi_detach(dsi);
-	if (err < 0)
-		dev_err(&dsi->dev, "failed to detach from DSI host: %d\n", err);
 
 	drm_panel_remove(&tdo_tl070wsh30->base);
 }
--
2.55.0