[PATCH] drm/i2c: tda998x: Choose between atomic or non atomic dpms helper

[Jyri Sarha <jsarha@ti.com>]

Choose between atomic or non atomic connector dpms helper. If tda998x
is connected to a drm driver that does not support atomic modeset
calling drm_atomic_helper_connector_dpms() causes a crash when the
connectors atomic state is not initialized. The patch implements a
driver specific connector dpms helper that calls
drm_atomic_helper_connector_dpms() if driver supports DRIVER_ATOMIC
and otherwise it calls the legacy drm_helper_connector_dpms().

Fixes commit 9736e988d328 ("drm/i2c: tda998x: Add support for atomic
modesetting").

Signed-off-by: Jyri Sarha <jsarha@ti.com>
---

Ok, so this is the second approach to solve this issue. The first
attempt can be found here [1] with the follow from Liviu Dudau that
suggested this approach. 

It just makes me wonder if drm_atomic_helper_connector_dpms() should
call the legacy callback automatically if DRIVER_ATOMIC is not set or
at least bail out gracefully with an error message. Then again it may
be overkill if the tda998x is the only driver that need to support
both situations.

Best regards,
Jyri

[1] http://www.spinics.net/lists/dri-devel/msg98514.html

 drivers/gpu/drm/i2c/tda998x_drv.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
index 012d36d..bb7d507 100644
--- a/drivers/gpu/drm/i2c/tda998x_drv.c
+++ b/drivers/gpu/drm/i2c/tda998x_drv.c
@@ -1382,8 +1382,16 @@ static void tda998x_connector_destroy(struct drm_connector *connector)
 	drm_connector_cleanup(connector);
 }
 
+static int tda998x_connector_dpms(struct drm_connector *connector, int mode)
+{
+	if (drm_core_check_feature(connector->dev, DRIVER_ATOMIC))
+		return drm_atomic_helper_connector_dpms(connector, mode);
+	else
+		return drm_helper_connector_dpms(connector, mode);
+}
+
 static const struct drm_connector_funcs tda998x_connector_funcs = {
-	.dpms = drm_atomic_helper_connector_dpms,
+	.dpms = tda998x_connector_dpms,
 	.reset = drm_atomic_helper_connector_reset,
 	.fill_modes = drm_helper_probe_single_connector_modes,
 	.detect = tda998x_connector_detect,
-- 
1.9.1

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