On Thu, May 03, 2018 at 06:40:08PM +0200, Boris Brezillon wrote:
> Having a device with a status property != "okay" in the DT is a valid
> use case, and we should not prevent the registration of the DRM device
> when the DSI device connected to the DSI controller is disabled.
>
> Consider the ENODEV return code as a valid result and do not expose the
> DSI encoder/connector when it happens.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxx>
> ---
> drivers/gpu/drm/vc4/vc4_dsi.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
> index 8aa897835118..db2f137f8b7b 100644
> --- a/drivers/gpu/drm/vc4/vc4_dsi.c
> +++ b/drivers/gpu/drm/vc4/vc4_dsi.c
> @@ -1606,8 +1606,18 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
>
> ret = drm_of_find_panel_or_bridge(dev->of_node, 0, 0,
> &panel, &dsi->bridge);
> - if (ret)
> + if (ret) {
> + /* If the bridge or panel pointed by dev->of_node is not
> + * enabled, just return 0 here so that we don't prevent the DRM
> + * dev from being registered. Of course that means the DSI
> + * encoder won't be exposed, but that's not a problem since
> + * nothing is connected to it.
> + */
> + if (ret == -ENODEV)
> + return 0;
> +
> return ret;
> + }
>
> if (panel) {
> dsi->bridge = devm_drm_panel_bridge_add(dev, panel,
> @@ -1652,7 +1662,8 @@ static void vc4_dsi_unbind(struct device *dev, struct device *master,
> struct vc4_dev *vc4 = to_vc4_dev(drm);
> struct vc4_dsi *dsi = dev_get_drvdata(dev);
>
> - pm_runtime_disable(dev);
> + if (dsi->bridge)
> + pm_runtime_disable(dev);
Is this safe? This uses component/master, so dsi->bridge is going to
remain valid until the driver's ->remove() is called. So technically you
could have a situation where drm_of_find_panel_or_bridge() returned some
error code that remains stored in dsi->bridge and cause the above
condition to be incorrectly true.
Thierry
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