[PATCH] drm/sun4i: Clear encoder->bridge if a bridge is not found

On Tue, Aug 30, 2016 at 11:51:26PM +0800, Chen-Yu Tsai wrote:

On Tue, Aug 30, 2016 at 8:56 PM, Maxime Ripard
[off-list ref] wrote:

quoted

Hi,

On Tue, Aug 30, 2016 at 08:22:23PM +0800, Chen-Yu Tsai wrote:

quoted

The KMS helpers (drm_atomic_helper_check_modeset/mode_fixup) pass
encoder->bridge directly to drm_bridge_mode_fixup, which expects a
valid pointer, or NULL (in which case it just returns).

Clear encoder->bridge if a bridge is not found, instead of keeping
the ERR_PTR value.

Since other drm_bridge functions also follow this pattern of checking
for a non-NULL pointer, we can drop the ifs around the calls and just
pass the pointer directly.

Fixes: 894f5a9f4b4a ("drm/sun4i: Add bridge support")
Signed-off-by: Chen-Yu Tsai <redacted>
---
 drivers/gpu/drm/sun4i/sun4i_rgb.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun4i_rgb.c b/drivers/gpu/drm/sun4i/sun4i_rgb.c
index d4e52522ec53..ee0795152a33 100644
--- a/drivers/gpu/drm/sun4i/sun4i_rgb.c
+++ b/drivers/gpu/drm/sun4i/sun4i_rgb.c

@@ -154,8 +154,7 @@ static void sun4i_rgb_encoder_enable(struct drm_encoder *encoder)
      if (!IS_ERR(tcon->panel))
              drm_panel_enable(tcon->panel);

-     if (!IS_ERR(encoder->bridge))
-             drm_bridge_enable(encoder->bridge);
+     drm_bridge_enable(encoder->bridge);

      sun4i_tcon_channel_enable(tcon, 0);
 }

@@ -170,8 +169,7 @@ static void sun4i_rgb_encoder_disable(struct drm_encoder *encoder)

      sun4i_tcon_channel_disable(tcon, 0);

-     if (!IS_ERR(encoder->bridge))
-             drm_bridge_disable(encoder->bridge);
+     drm_bridge_disable(encoder->bridge);

I'd rather keep those changes, it makes it obvious that it's something
optionnal, that can be set to NULL.

OK.

quoted

quoted

      if (!IS_ERR(tcon->panel))
              drm_panel_disable(tcon->panel);

@@ -230,6 +228,9 @@ int sun4i_rgb_init(struct drm_device *drm)
              return 0;
      }

+     if (IS_ERR(encoder->bridge))
+             encoder->bridge = NULL;
+

And that could be the else condition of the if statement below.

That would be a bit confusing, changing it after calling drm_encoder_init.
The code says it ok to do though.

The magic really happens only after the encoder has been attached to
something, so it's really safe.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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