Re: [PATCH v2 01/13] drm/msm/dsi: switch to devm_drm_bridge_add()

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On 10/9/2023 12:01 PM, Dmitry Baryshkov wrote:
On 09/10/2023 21:51, Abhinav Kumar wrote:


On 10/9/2023 11:46 AM, Dmitry Baryshkov wrote:
On 09/10/2023 21:39, Abhinav Kumar wrote:


On 10/9/2023 11:10 AM, Dmitry Baryshkov wrote:
Make MSM DSI driver use devm_drm_bridge_add() instead of plain
drm_bridge_add(). As the driver doesn't require any additional cleanup,
stop adding created bridge to the priv->bridges array.

Reviewed-by: Rob Clark <robdclark@xxxxxxxxx>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
---
  drivers/gpu/drm/msm/dsi/dsi.c         | 28 +++++--------------------
  drivers/gpu/drm/msm/dsi/dsi.h         |  3 +--
  drivers/gpu/drm/msm/dsi/dsi_manager.c | 30 +++++++++------------------
  3 files changed, 16 insertions(+), 45 deletions(-)

diff --git a/drivers/gpu/drm/msm/dsi/dsi.c b/drivers/gpu/drm/msm/dsi/dsi.c
index d45e43024802..47f327e68471 100644
--- a/drivers/gpu/drm/msm/dsi/dsi.c
+++ b/drivers/gpu/drm/msm/dsi/dsi.c
@@ -215,20 +215,14 @@ void __exit msm_dsi_unregister(void)
  int msm_dsi_modeset_init(struct msm_dsi *msm_dsi, struct drm_device *dev,
               struct drm_encoder *encoder)
  {
-    struct msm_drm_private *priv = dev->dev_private;
      int ret;
-    if (priv->num_bridges == ARRAY_SIZE(priv->bridges)) {
-        DRM_DEV_ERROR(dev->dev, "too many bridges\n");
-        return -ENOSPC;
-    }
-
      msm_dsi->dev = dev;
      ret = msm_dsi_host_modeset_init(msm_dsi->host, dev);
      if (ret) {
          DRM_DEV_ERROR(dev->dev, "failed to modeset init host: %d\n", ret);
-        goto fail;
+        return ret;
      }
      if (msm_dsi_is_bonded_dsi(msm_dsi) &&
@@ -242,32 +236,20 @@ int msm_dsi_modeset_init(struct msm_dsi *msm_dsi, struct drm_device *dev,
      msm_dsi->encoder = encoder;
-    msm_dsi->bridge = msm_dsi_manager_bridge_init(msm_dsi->id);
-    if (IS_ERR(msm_dsi->bridge)) {
-        ret = PTR_ERR(msm_dsi->bridge);
+    ret = msm_dsi_manager_bridge_init(msm_dsi);
+    if (ret) {
          DRM_DEV_ERROR(dev->dev, "failed to create dsi bridge: %d\n", ret);
-        msm_dsi->bridge = NULL;
-        goto fail;
+        return ret;
      }
      ret = msm_dsi_manager_ext_bridge_init(msm_dsi->id);
      if (ret) {
          DRM_DEV_ERROR(dev->dev,
              "failed to create dsi connector: %d\n", ret);
-        goto fail;
+        return ret;
      }
-    priv->bridges[priv->num_bridges++]       = msm_dsi->bridge;
-
      return 0;
-fail:
-    /* bridge/connector are normally destroyed by drm: */
-    if (msm_dsi->bridge) {
-        msm_dsi_manager_bridge_destroy(msm_dsi->bridge);
-        msm_dsi->bridge = NULL;
-    }

We can drop msm_dsi_manager_bridge_destroy() now but dont we need to keep the part to reset msm_dsi->bridge to NULL in the fail tag if msm_dsi_manager_ext_bridge_init() fails?

What for? This field is not read in the error /unbinding path.
I'll send a followup that drops msm_dsi->bridge completely.


Not used in the error path. The behavior before this patch was, if msm_dsi_manager_ext_bridge_init failed, it was marking msm_dsi->bridge as NULL. Thats what I thought you would want to retain till you drop the msm_dsi->bridge.

Why would you like to keep the useless behaviour?


Not sure whether to call it useless. So msm_dsi_manager_ext_bridge_init() is referencing msm_dsi->bridge. msm_dsi_manager_ext_bridge_init() is an exported API. If someone tries to call it outside of where its called now, this was the only protection against the access?

I guess, you could counter argue that noone calls it that way today.

In that sense, I am fine with this, just wanted to report the gap after this patch before I ack.

OR you can even add that line in the if (ret) of msm_dsi_manager_ext_bridge_init(msm_dsi->id); failure.


-
-    return ret;
  }
  void msm_dsi_snapshot(struct msm_disp_state *disp_state, struct msm_dsi *msm_dsi) diff --git a/drivers/gpu/drm/msm/dsi/dsi.h b/drivers/gpu/drm/msm/dsi/dsi.h
index d21867da78b8..a01c326774a6 100644
--- a/drivers/gpu/drm/msm/dsi/dsi.h
+++ b/drivers/gpu/drm/msm/dsi/dsi.h
@@ -56,8 +56,7 @@ struct msm_dsi {
  };
  /* dsi manager */
-struct drm_bridge *msm_dsi_manager_bridge_init(u8 id);
-void msm_dsi_manager_bridge_destroy(struct drm_bridge *bridge);
+int msm_dsi_manager_bridge_init(struct msm_dsi *msm_dsi);
  int msm_dsi_manager_ext_bridge_init(u8 id);
  int msm_dsi_manager_cmd_xfer(int id, const struct mipi_dsi_msg *msg);   bool msm_dsi_manager_cmd_xfer_trigger(int id, u32 dma_base, u32 len); diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c b/drivers/gpu/drm/msm/dsi/dsi_manager.c
index 28b8012a21f2..17aa19bb6510 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_manager.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c
@@ -466,9 +466,8 @@ static const struct drm_bridge_funcs dsi_mgr_bridge_funcs = {
  };
  /* initialize bridge */
-struct drm_bridge *msm_dsi_manager_bridge_init(u8 id)
+int msm_dsi_manager_bridge_init(struct msm_dsi *msm_dsi)
  {
-    struct msm_dsi *msm_dsi = dsi_mgr_get_dsi(id);
      struct drm_bridge *bridge = NULL;
      struct dsi_bridge *dsi_bridge;
      struct drm_encoder *encoder;
@@ -476,31 +475,27 @@ struct drm_bridge *msm_dsi_manager_bridge_init(u8 id)
      dsi_bridge = devm_kzalloc(msm_dsi->dev->dev,
                  sizeof(*dsi_bridge), GFP_KERNEL);
-    if (!dsi_bridge) {
-        ret = -ENOMEM;
-        goto fail;
-    }
+    if (!dsi_bridge)
+        return -ENOMEM;
-    dsi_bridge->id = id;
+    dsi_bridge->id = msm_dsi->id;
      encoder = msm_dsi->encoder;
      bridge = &dsi_bridge->base;
      bridge->funcs = &dsi_mgr_bridge_funcs;
-    drm_bridge_add(bridge);
+    ret = devm_drm_bridge_add(&msm_dsi->pdev->dev, bridge);
+    if (ret)
+        return ret;
      ret = drm_bridge_attach(encoder, bridge, NULL, 0);
      if (ret)
-        goto fail;
+        return ret;
-    return bridge;
+    msm_dsi->bridge = bridge;
-fail:
-    if (bridge)
-        msm_dsi_manager_bridge_destroy(bridge);
-
-    return ERR_PTR(ret);
+    return 0;
  }
  int msm_dsi_manager_ext_bridge_init(u8 id)
@@ -557,11 +552,6 @@ int msm_dsi_manager_ext_bridge_init(u8 id)
      return 0;
  }
-void msm_dsi_manager_bridge_destroy(struct drm_bridge *bridge)
-{
-    drm_bridge_remove(bridge);
-}
-
  int msm_dsi_manager_cmd_xfer(int id, const struct mipi_dsi_msg *msg)
  {
      struct msm_dsi *msm_dsi = dsi_mgr_get_dsi(id);





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