Re: [PATCH v3 02/10] drm/display: add CEC helpers code

[Maxime Ripard <mripard@kernel.org>]

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On Wed, Feb 05, 2025 at 05:01:09PM +0200, Dmitry Baryshkov wrote:
> On Wed, Feb 05, 2025 at 03:27:05PM +0100, Maxime Ripard wrote:
> > On Tue, Jan 28, 2025 at 02:17:19PM +0200, Dmitry Baryshkov wrote:
> > > On Tue, Jan 28, 2025 at 11:36:06AM +0100, Maxime Ripard wrote:
> > > > On Sun, Jan 26, 2025 at 03:29:07PM +0200, Dmitry Baryshkov wrote:
> > > > > Add generic CEC helpers to be used by HDMI drivers. Both notifier and
> > > > > and adapter are supported for registration. Once registered, the driver
> > > > > can call common set of functions to update physical address, to
> > > > > invalidate it or to unregister CEC data.
> > > > > 
> > > > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> > > > > ---
> > > > >  drivers/gpu/drm/display/Kconfig               |   5 +
> > > > >  drivers/gpu/drm/display/Makefile              |   2 +
> > > > >  drivers/gpu/drm/display/drm_hdmi_cec_helper.c | 209 ++++++++++++++++++++++++++
> > > > >  include/drm/display/drm_hdmi_cec_helper.h     |  61 ++++++++
> > > > >  4 files changed, 277 insertions(+)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/display/Kconfig b/drivers/gpu/drm/display/Kconfig
> > > > > index 8d22b7627d41f7bc015decf24ae02a05bc00f055..49da9b768acf3e5f84f2cefae4bb042cfd57a50c 100644
> > > > > --- a/drivers/gpu/drm/display/Kconfig
> > > > > +++ b/drivers/gpu/drm/display/Kconfig
> > > > > @@ -82,6 +82,11 @@ config DRM_DISPLAY_HDMI_AUDIO_HELPER
> > > > >  	  DRM display helpers for HDMI Audio functionality (generic HDMI Codec
> > > > >  	  implementation).
> > > > >  
> > > > > +config DRM_DISPLAY_HDMI_CEC_HELPER
> > > > > +	bool
> > > > > +	help
> > > > > +	  DRM display helpers for HDMI CEC implementation.
> > > > > +
> > > > >  config DRM_DISPLAY_HDMI_HELPER
> > > > >  	bool
> > > > >  	help
> > > > > diff --git a/drivers/gpu/drm/display/Makefile b/drivers/gpu/drm/display/Makefile
> > > > > index b17879b957d5401721396e247fa346387cf6c48a..2cd078e2b81c1a9e6b336c4187b444bcb8a50e51 100644
> > > > > --- a/drivers/gpu/drm/display/Makefile
> > > > > +++ b/drivers/gpu/drm/display/Makefile
> > > > > @@ -16,6 +16,8 @@ drm_display_helper-$(CONFIG_DRM_DISPLAY_DSC_HELPER) += \
> > > > >  drm_display_helper-$(CONFIG_DRM_DISPLAY_HDCP_HELPER) += drm_hdcp_helper.o
> > > > >  drm_display_helper-$(CONFIG_DRM_DISPLAY_HDMI_AUDIO_HELPER) += \
> > > > >  	drm_hdmi_audio_helper.o
> > > > > +drm_display_helper-$(CONFIG_DRM_DISPLAY_HDMI_CEC_HELPER) += \
> > > > > +	drm_hdmi_cec_helper.o
> > > > >  drm_display_helper-$(CONFIG_DRM_DISPLAY_HDMI_HELPER) += \
> > > > >  	drm_hdmi_helper.o \
> > > > >  	drm_scdc_helper.o
> > > > > diff --git a/drivers/gpu/drm/display/drm_hdmi_cec_helper.c b/drivers/gpu/drm/display/drm_hdmi_cec_helper.c
> > > > > new file mode 100644
> > > > > index 0000000000000000000000000000000000000000..a6ed5f0fc3835b013a83308f5285ea0819c5702c
> > > > > --- /dev/null
> > > > > +++ b/drivers/gpu/drm/display/drm_hdmi_cec_helper.c
> > > > > @@ -0,0 +1,209 @@
> > > > > +// SPDX-License-Identifier: MIT
> > > > > +/*
> > > > > + * Copyright (c) 2024 Linaro Ltd
> > > > > + */
> > > > > +
> > > > > +#include <drm/drm_bridge.h>
> > > > > +#include <drm/drm_connector.h>
> > > > > +#include <drm/display/drm_hdmi_cec_helper.h>
> > > > > +
> > > > > +#include <linux/mutex.h>
> > > > > +
> > > > > +#include <media/cec.h>
> > > > > +#include <media/cec-notifier.h>
> > > > > +
> > > > > +void drm_connector_hdmi_cec_unregister(struct drm_connector *connector)
> > > > > +{
> > > > > +	cec_unregister_adapter(connector->cec.adapter);
> > > > > +	connector->cec.adapter = NULL;
> > > > > +
> > > > > +	cec_notifier_conn_unregister(connector->cec.notifier);
> > > > > +	connector->cec.notifier = NULL;
> > > > > +
> > > > > +	connector->cec.funcs = NULL;
> > > > > +}
> > > > > +EXPORT_SYMBOL(drm_connector_hdmi_cec_unregister);
> > > > > +
> > > > > +static const struct drm_connector_cec_funcs drm_connector_hdmi_cec_funcs = {
> > > > > +	.unregister = drm_connector_hdmi_cec_unregister,
> > > > > +};
> > > > > +
> > > > > +int drm_connector_hdmi_cec_notifier_register(struct drm_connector *connector,
> > > > > +					     const char *port_name,
> > > > > +					     struct device *dev)
> > > > > +{
> > > > > +	struct cec_connector_info conn_info;
> > > > > +	struct cec_notifier *notifier;
> > > > > +	int ret;
> > > > > +
> > > > > +	mutex_lock(&connector->cec.mutex);
> > > > > +
> > > > > +	if (connector->cec.funcs) {
> > > > > +		ret = -EBUSY;
> > > > > +		goto err_unlock;
> > > > > +	}
> > > > > +
> > > > > +	cec_fill_conn_info_from_drm(&conn_info, connector);
> > > > > +
> > > > > +	notifier = cec_notifier_conn_register(dev, port_name, &conn_info);
> > > > > +	if (!notifier) {
> > > > > +		ret = -ENOMEM;
> > > > > +		goto err_unlock;
> > > > > +	}
> > > > > +
> > > > > +	connector->cec.notifier = notifier;
> > > > > +	connector->cec.funcs = &drm_connector_hdmi_cec_funcs;
> > > > > +
> > > > > +	mutex_unlock(&connector->cec.mutex);
> > > > > +
> > > > > +	return 0;
> > > > > +
> > > > > +err_unlock:
> > > > > +	mutex_unlock(&connector->cec.mutex);
> > > > > +
> > > > > +	return ret;
> > > > > +}
> > > > > +EXPORT_SYMBOL(drm_connector_hdmi_cec_notifier_register);
> > > > > +
> > > > > +#define to_hdmi_cec_adapter_ops(ops) \
> > > > > +	container_of(ops, struct drm_connector_hdmi_cec_adapter_ops, base)
> > > > > +
> > > > > +static int drm_connector_hdmi_cec_adap_enable(struct cec_adapter *adap, bool enable)
> > > > > +{
> > > > > +	struct drm_connector *connector = cec_get_drvdata(adap);
> > > > > +	struct drm_connector_hdmi_cec_adapter_ops *ops =
> > > > > +		to_hdmi_cec_adapter_ops(connector->cec.funcs);
> > > > > +
> > > > > +	return ops->enable(connector, enable);
> > > > > +}
> > > > > +
> > > > > +static int drm_connector_hdmi_cec_adap_log_addr(struct cec_adapter *adap, u8 logical_addr)
> > > > > +{
> > > > > +	struct drm_connector *connector = cec_get_drvdata(adap);
> > > > > +	struct drm_connector_hdmi_cec_adapter_ops *ops =
> > > > > +		to_hdmi_cec_adapter_ops(connector->cec.funcs);
> > > > > +
> > > > > +	return ops->log_addr(connector, logical_addr);
> > > > > +}
> > > > > +
> > > > > +static int drm_connector_hdmi_cec_adap_transmit(struct cec_adapter *adap, u8 attempts,
> > > > > +						u32 signal_free_time, struct cec_msg *msg)
> > > > > +{
> > > > > +	struct drm_connector *connector = cec_get_drvdata(adap);
> > > > > +	struct drm_connector_hdmi_cec_adapter_ops *ops =
> > > > > +		to_hdmi_cec_adapter_ops(connector->cec.funcs);
> > > > > +
> > > > > +	return ops->transmit(connector, attempts, signal_free_time, msg);
> > > > > +}
> > > > > +
> > > > > +static const struct cec_adap_ops drm_connector_hdmi_cec_adap_ops = {
> > > > > +	.adap_enable = drm_connector_hdmi_cec_adap_enable,
> > > > > +	.adap_log_addr = drm_connector_hdmi_cec_adap_log_addr,
> > > > > +	.adap_transmit = drm_connector_hdmi_cec_adap_transmit,
> > > > > +};
> > > > > +
> > > > > +int drm_connector_hdmi_cec_register(struct drm_connector *connector,
> > > > > +				    const struct drm_connector_hdmi_cec_adapter_ops *ops,
> > > > > +				    const char *name,
> > > > > +				    u8 available_las,
> > > > > +				    struct device *dev)
> > > > > +{
> > > > > +	struct cec_connector_info conn_info;
> > > > > +	struct cec_adapter *cec_adap;
> > > > > +	int ret;
> > > > > +
> > > > > +	if (!ops->base.unregister ||
> > > > > +	    !ops->init || !ops->enable || !ops->log_addr || !ops->transmit)
> > > > > +		return -EINVAL;
> > > > > +
> > > > > +	mutex_lock(&connector->cec.mutex);
> > > > > +
> > > > > +	if (connector->cec.funcs) {
> > > > > +		ret = -EBUSY;
> > > > > +		goto err_unlock;
> > > > > +	}
> > > > > +
> > > > > +	cec_adap = cec_allocate_adapter(&drm_connector_hdmi_cec_adap_ops, connector, name,
> > > > > +					CEC_CAP_DEFAULTS | CEC_CAP_CONNECTOR_INFO,
> > > > > +					available_las ? : CEC_MAX_LOG_ADDRS);
> > > > > +	ret = PTR_ERR_OR_ZERO(cec_adap);
> > > > > +	if (ret < 0)
> > > > > +		goto err_unlock;
> > > > > +
> > > > > +	cec_fill_conn_info_from_drm(&conn_info, connector);
> > > > > +	cec_s_conn_info(cec_adap, &conn_info);
> > > > > +
> > > > > +	connector->cec.adapter = cec_adap;
> > > > > +	connector->cec.funcs = &ops->base;
> > > > > +
> > > > > +	ret = ops->init(connector);
> > > > > +	if (ret < 0)
> > > > > +		goto err_delete_adapter;
> > > > > +
> > > > > +	ret = cec_register_adapter(cec_adap, dev);
> > > > > +	if (ret < 0)
> > > > > +		goto err_delete_adapter;
> > > > > +
> > > > > +	mutex_unlock(&connector->cec.mutex);
> > > > > +
> > > > > +	return 0;
> > > > > +
> > > > > +err_delete_adapter:
> > > > > +	cec_delete_adapter(cec_adap);
> > > > > +
> > > > > +	connector->cec.adapter = NULL;
> > > > > +
> > > > > +err_unlock:
> > > > > +	mutex_unlock(&connector->cec.mutex);
> > > > > +
> > > > > +	return ret;
> > > > > +}
> > > > > +EXPORT_SYMBOL(drm_connector_hdmi_cec_register);
> > > > > +
> > > > > +void drm_connector_hdmi_cec_received_msg(struct drm_connector *connector,
> > > > > +					 struct cec_msg *msg)
> > > > > +{
> > > > > +	cec_received_msg(connector->cec.adapter, msg);
> > > > > +}
> > > > > +EXPORT_SYMBOL(drm_connector_hdmi_cec_received_msg);
> > > > > +
> > > > > +void drm_connector_hdmi_cec_transmit_attempt_done(struct drm_connector *connector,
> > > > > +						  u8 status)
> > > > > +{
> > > > > +	cec_transmit_attempt_done(connector->cec.adapter, status);
> > > > > +}
> > > > > +EXPORT_SYMBOL(drm_connector_hdmi_cec_transmit_attempt_done);
> > > > > +
> > > > > +void drm_connector_hdmi_cec_transmit_done(struct drm_connector *connector,
> > > > > +					  u8 status,
> > > > > +					  u8 arb_lost_cnt, u8 nack_cnt,
> > > > > +					  u8 low_drive_cnt, u8 error_cnt)
> > > > > +{
> > > > > +	cec_transmit_done(connector->cec.adapter, status,
> > > > > +			  arb_lost_cnt, nack_cnt, low_drive_cnt, error_cnt);
> > > > > +}
> > > > > +EXPORT_SYMBOL(drm_connector_hdmi_cec_transmit_done);
> > > > > +
> > > > > +void drm_connector_hdmi_cec_phys_addr_invalidate(struct drm_connector *connector)
> > > > > +{
> > > > > +	mutex_lock(&connector->cec.mutex);
> > > > > +
> > > > > +	cec_phys_addr_invalidate(connector->cec.adapter);
> > > > > +	cec_notifier_phys_addr_invalidate(connector->cec.notifier);
> > > > > +
> > > > > +	mutex_unlock(&connector->cec.mutex);
> > > > > +}
> > > > > +EXPORT_SYMBOL(drm_connector_hdmi_cec_phys_addr_invalidate);
> > > > > +
> > > > > +void drm_connector_hdmi_cec_phys_addr_set(struct drm_connector *connector)
> > > > > +{
> > > > > +	mutex_lock(&connector->cec.mutex);
> > > > > +
> > > > > +	cec_s_phys_addr(connector->cec.adapter,
> > > > > +			connector->display_info.source_physical_address, false);
> > > > > +	cec_notifier_set_phys_addr(connector->cec.notifier,
> > > > > +				   connector->display_info.source_physical_address);
> > > > > +
> > > > > +	mutex_unlock(&connector->cec.mutex);
> > > > > +}
> > > > > +EXPORT_SYMBOL(drm_connector_hdmi_cec_phys_addr_set);
> > > > > diff --git a/include/drm/display/drm_hdmi_cec_helper.h b/include/drm/display/drm_hdmi_cec_helper.h
> > > > > new file mode 100644
> > > > > index 0000000000000000000000000000000000000000..cd6274e4ee9b3e41a2d85289c4a420b854340e19
> > > > > --- /dev/null
> > > > > +++ b/include/drm/display/drm_hdmi_cec_helper.h
> > > > > @@ -0,0 +1,61 @@
> > > > > +/* SPDX-License-Identifier: MIT */
> > > > > +
> > > > > +#ifndef DRM_DISPLAY_HDMI_CEC_HELPER
> > > > > +#define DRM_DISPLAY_HDMI_CEC_HELPER
> > > > > +
> > > > > +#include <drm/drm_connector.h>
> > > > > +
> > > > > +#include <linux/types.h>
> > > > > +
> > > > > +struct drm_connector;
> > > > > +
> > > > > +struct cec_msg;
> > > > > +struct device;
> > > > > +
> > > > > +struct drm_connector_hdmi_cec_adapter_ops {
> > > > > +	struct drm_connector_cec_funcs base;
> > > > > +
> > > > > +	int (*init)(struct drm_connector *connector);
> > > > > +	void (*uninit)(struct drm_connector *connector);
> > > > > +
> > > > > +	int (*enable)(struct drm_connector *connector, bool enable);
> > > > > +	int (*log_addr)(struct drm_connector *connector, u8 logical_addr);
> > > > > +	int (*transmit)(struct drm_connector *connector, u8 attempts,
> > > > > +			u32 signal_free_time, struct cec_msg *msg);
> > > > > +};
> > > > 
> > > > Why can't we merge drm_connector_cec_funcs and
> > > > drm_connector_cec_adapter_ops? They look equivalent to me?
> > > 
> > > Well, not exactly. The funcs is a generic interface. Notifiers do not
> > > need the adapter_ops. And cec_pin (sun4i) would also require a different
> > > set of callbacks. Thus I decided that it's easier to subclass funcs
> > > instead of adding all possible callbacks there.
> > 
> > There's two things here: cec_pin and cec_adapter are equivalent. They
> > provide the same feature, but one relies on an hardware controller, the
> > other bitbangs a GPIO. They are also mutually exclusive.
> > 
> > So I'd very much expect a different set of hooks there.
> 
> That's the point. Normal CEC adapters would need to implement these
> callbacks. CEC pin adapter will have a different set of callbacks.
> Notifiers do not need any extra callbacks at all.

Sure, and that's true for most of the KMS entities we support. What I
don't get is why that dual layer func structure is needed in the first
place. We have no other entity that works that way, and we typically
solve this using a helper.

Maxime

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