Re: [PATCH v3 2/5] drm: bridge: dw-hdmi: Report connector status using callback

[Russell King - ARM Linux admin]

On Fri, Jul 12, 2019 at 06:04:40PM +0800, Cheng-Yi Chiang wrote:
> Allow codec driver register callback function for plug event.
> 
> The callback registration flow:
> dw-hdmi <--- hw-hdmi-i2s-audio <--- hdmi-codec
> 
> dw-hdmi-i2s-audio implements hook_plugged_cb op
> so codec driver can register the callback.
> 
> dw-hdmi implements set_plugged_cb op so platform device can register the
> callback.
> 
> When connector plug/unplug event happens, report this event using the
> callback.
> 
> Make sure that audio and drm are using the single source of truth for
> connector status.
> 
> Signed-off-by: Cheng-Yi Chiang <cychiang@xxxxxxxxxxxx>
> ---
>  .../gpu/drm/bridge/synopsys/dw-hdmi-audio.h   |  3 +
>  .../drm/bridge/synopsys/dw-hdmi-i2s-audio.c   | 10 ++++
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c     | 55 ++++++++++++++++++-
>  3 files changed, 67 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-audio.h b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-audio.h
> index 63b5756f463b..f523c590984e 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-audio.h
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-audio.h
> @@ -2,6 +2,8 @@
>  #ifndef DW_HDMI_AUDIO_H
>  #define DW_HDMI_AUDIO_H
>  
> +#include <sound/hdmi-codec.h>
> +
>  struct dw_hdmi;
>  
>  struct dw_hdmi_audio_data {
> @@ -17,6 +19,7 @@ struct dw_hdmi_i2s_audio_data {
>  
>  	void (*write)(struct dw_hdmi *hdmi, u8 val, int offset);
>  	u8 (*read)(struct dw_hdmi *hdmi, int offset);
> +	int (*set_plugged_cb)(struct dw_hdmi *hdmi, hdmi_codec_plugged_cb fn);
>  };
>  
>  #endif
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> index 5cbb71a866d5..7b93cf05c985 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c
> @@ -104,10 +104,20 @@ static int dw_hdmi_i2s_get_dai_id(struct snd_soc_component *component,
>  	return -EINVAL;
>  }
>  
> +static int dw_hdmi_i2s_hook_plugged_cb(struct device *dev, void *data,
> +				       hdmi_codec_plugged_cb fn)
> +{
> +	struct dw_hdmi_i2s_audio_data *audio = data;
> +	struct dw_hdmi *hdmi = audio->hdmi;
> +
> +	return audio->set_plugged_cb(hdmi, fn);
> +}
> +
>  static struct hdmi_codec_ops dw_hdmi_i2s_ops = {
>  	.hw_params	= dw_hdmi_i2s_hw_params,
>  	.audio_shutdown	= dw_hdmi_i2s_audio_shutdown,
>  	.get_dai_id	= dw_hdmi_i2s_get_dai_id,
> +	.hook_plugged_cb = dw_hdmi_i2s_hook_plugged_cb,
>  };
>  
>  static int snd_dw_hdmi_probe(struct platform_device *pdev)
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 045b1b13fd0e..ce6646067472 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -26,6 +26,8 @@
>  #include <drm/drm_probe_helper.h>
>  #include <drm/bridge/dw_hdmi.h>
>  
> +#include <sound/hdmi-codec.h>
> +
>  #include <uapi/linux/media-bus-format.h>
>  #include <uapi/linux/videodev2.h>
>  
> @@ -185,6 +187,9 @@ struct dw_hdmi {
>  	void (*disable_audio)(struct dw_hdmi *hdmi);
>  
>  	struct cec_notifier *cec_notifier;
> +
> +	hdmi_codec_plugged_cb plugged_cb;
> +	enum drm_connector_status last_connector_result;
>  };
>  
>  #define HDMI_IH_PHY_STAT0_RX_SENSE \
> @@ -209,6 +214,40 @@ static inline u8 hdmi_readb(struct dw_hdmi *hdmi, int offset)
>  	return val;
>  }
>  
> +static void handle_plugged_change(struct dw_hdmi *hdmi, bool plugged)
> +{
> +	struct platform_device *codec_pdev;
> +
> +	if (!hdmi->audio || IS_ERR(hdmi->audio))
> +		return;
> +	codec_pdev = platform_get_drvdata(hdmi->audio);
> +	if (!codec_pdev || IS_ERR(codec_pdev))
> +		return;

This looks fragile to me, poking about in another device's driver data
from another driver is really not a good design decision.  I think this
can be simplified if the registration function took the function
pointer and the struct device pointer, and then you only need one test
below:

> +	if (!hdmi->plugged_cb)
> +		return;
> +
> +	hdmi->plugged_cb(&codec_pdev->dev, plugged);
> +}
> +
> +static int hdmi_set_plugged_cb(struct dw_hdmi *hdmi, hdmi_codec_plugged_cb fn)
> +{
> +	bool plugged;
> +	struct platform_device *codec_pdev;
> +
> +	if (!hdmi->audio || IS_ERR(hdmi->audio))
> +		return -EINVAL;

Given the current code structure, how can this ever be true when the
function is called?

> +	codec_pdev = platform_get_drvdata(hdmi->audio);
> +	if (!codec_pdev || IS_ERR(codec_pdev))
> +		return -EINVAL;

This doesn't seem like a good idea as I've pointed out above.

> +
> +	mutex_lock(&hdmi->mutex);
> +	hdmi->plugged_cb = fn;
> +	plugged = hdmi->last_connector_result == connector_status_connected;
> +	handle_plugged_change(hdmi, plugged);
> +	mutex_unlock(&hdmi->mutex);

Should be a blank line here for readability.

> +	return 0;
> +}
> +
>  static void hdmi_modb(struct dw_hdmi *hdmi, u8 data, u8 mask, unsigned reg)
>  {
>  	regmap_update_bits(hdmi->regm, reg << hdmi->reg_shift, mask, data);
> @@ -2044,6 +2083,7 @@ dw_hdmi_connector_detect(struct drm_connector *connector, bool force)
>  {
>  	struct dw_hdmi *hdmi = container_of(connector, struct dw_hdmi,
>  					     connector);
> +	enum drm_connector_status result;
>  
>  	mutex_lock(&hdmi->mutex);
>  	hdmi->force = DRM_FORCE_UNSPECIFIED;
> @@ -2051,7 +2091,18 @@ dw_hdmi_connector_detect(struct drm_connector *connector, bool force)
>  	dw_hdmi_update_phy_mask(hdmi);
>  	mutex_unlock(&hdmi->mutex);
>  
> -	return hdmi->phy.ops->read_hpd(hdmi, hdmi->phy.data);
> +	result = hdmi->phy.ops->read_hpd(hdmi, hdmi->phy.data);
> +
> +	mutex_lock(&hdmi->mutex);
> +	if (result != hdmi->last_connector_result) {
> +		dev_dbg(hdmi->dev, "read_hpd result: %d", result);
> +		handle_plugged_change(hdmi,
> +				      result == connector_status_connected);
> +		hdmi->last_connector_result = result;
> +	}
> +	mutex_unlock(&hdmi->mutex);
> +
> +	return result;
>  }
>  
>  static int dw_hdmi_connector_get_modes(struct drm_connector *connector)
> @@ -2460,6 +2511,7 @@ __dw_hdmi_probe(struct platform_device *pdev,
>  	hdmi->rxsense = true;
>  	hdmi->phy_mask = (u8)~(HDMI_PHY_HPD | HDMI_PHY_RX_SENSE);
>  	hdmi->mc_clkdis = 0x7f;
> +	hdmi->last_connector_result = connector_status_disconnected;
>  
>  	mutex_init(&hdmi->mutex);
>  	mutex_init(&hdmi->audio_mutex);
> @@ -2653,6 +2705,7 @@ __dw_hdmi_probe(struct platform_device *pdev,
>  		audio.hdmi	= hdmi;
>  		audio.write	= hdmi_writeb;
>  		audio.read	= hdmi_readb;
> +		audio.set_plugged_cb = hdmi_set_plugged_cb;

Why is this necessary?

The I2S audio driver already depends on the dw-hdmi module through its
use of functions already exported.  Indirecting this through the
platform data makes no sense.

Just rename hdmi_set_plugged_cb to dw_hdmi_set_plugged_cb() and export
it for dw-hdmi-i2s-audio.c to use.

Thanks.

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