Re: [Intel-gfx] [PATCH 2/2] drm/msm/dp: Implement oob_hotplug_event()

Greg Kroah-Hartman
2022-02-08T07:40:46Z

On Mon, Feb 07, 2022 at 08:43:28PM -0800, Bjorn Andersson wrote:
> The Qualcomm DisplayPort driver contains traces of the necessary
> plumbing to hook up USB HPD, in the form of the dp_hpd module and the
> dp_usbpd_cb struct. Use this as basis for implementing the
> oob_hotplug_event() callback, by amending the dp_hpd module with the
> missing logic.
>
> Overall the solution is similar to what's done downstream, but upstream
> all the code to disect the HPD notification lives on the calling side of
> drm_connector_oob_hotplug_event().
>
> drm_connector_oob_hotplug_event() performs the lookup of the
> drm_connector based on fwnode, hence the need to assign the fwnode in
> dp_drm_connector_init().
>
> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> ---
> drivers/gpu/drm/msm/dp/dp_display.c | 8 ++++++++
> drivers/gpu/drm/msm/dp/dp_display.h | 2 ++
> drivers/gpu/drm/msm/dp/dp_drm.c | 10 ++++++++++
> drivers/gpu/drm/msm/dp/dp_hpd.c | 19 +++++++++++++++++++
> drivers/gpu/drm/msm/dp/dp_hpd.h | 4 ++++
> 5 files changed, 43 insertions(+)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index 7cc4d21f2091..124a2f794382 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -414,6 +414,13 @@ static int dp_display_usbpd_configure_cb(struct device *dev)
> return dp_display_process_hpd_high(dp);
> }
>
> +void dp_display_oob_hotplug_event(struct msm_dp *dp_display, bool hpd_state)
> +{
> + struct dp_display_private *dp = container_of(dp_display, struct dp_display_private, dp_display);
> +
> + dp->usbpd->oob_event(dp->usbpd, hpd_state);
> +}
> +
> static int dp_display_usbpd_disconnect_cb(struct device *dev)
> {
> struct dp_display_private *dp = dev_get_dp_display_private(dev);
> @@ -1251,6 +1258,7 @@ static int dp_display_probe(struct platform_device *pdev)
> dp->pdev = pdev;
> dp->name = "drm_dp";
> dp->dp_display.connector_type = desc->connector_type;
> + dp->dp_display.dev = &pdev->dev;

You did not properly reference count this pointer you just saved. What
is to keep that pointer from going away without you knowing about it?

And you already have a pointer to pdev, why save another one here?

>
> rc = dp_init_sub_modules(dp);
> if (rc) {
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.h b/drivers/gpu/drm/msm/dp/dp_display.h
> index e3adcd578a90..1f856b3bca79 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.h
> +++ b/drivers/gpu/drm/msm/dp/dp_display.h
> @@ -11,6 +11,7 @@
> #include "disp/msm_disp_snapshot.h"
>
> struct msm_dp {
> + struct device *dev;
> struct drm_device *drm_dev;
> struct device *codec_dev;

So you now have pointers to 3 different devices here? What does 'dev'
point to that the other ones do not? This needs to be documented really
well here.

thanks,

greg k-h