Re: [PATCH 1/7] video: add HDMI state notifier support

From: Cheng-yi Chiang
Date: Mon Jun 03 2019 - 22:37:12 EST

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On Mon, Jun 3, 2019 at 4:09 PM Daniel Vetter <daniel@xxxxxxxx> wrote:
>
> On Mon, Jun 03, 2019 at 09:45:49AM +0200, Hans Verkuil wrote:
> > On 6/3/19 6:32 AM, Cheng-Yi Chiang wrote:
> > > From: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> > >
> > > Add support for HDMI hotplug and EDID notifiers, which is used to convey
> > > information from HDMI drivers to their CEC and audio counterparts.
> > >
> > > Based on an earlier version from Russell King:
> > >
> > > https://patchwork.kernel.org/patch/9277043/
> > >
> > > The hdmi_notifier is a reference counted object containing the HDMI state
> > > of an HDMI device.
> > >
> > > When a new notifier is registered the current state will be reported to
> > > that notifier at registration time.
> > >
> > > Based on Hans Verkuil's patch:
> > >
> > > https://patchwork.kernel.org/patch/9472521/
> >
> > Erm, you are aware that this patch morphed into a CEC-specific notifier
> > found in drivers/media/cec/cec-notifier.c?
> >
> > I don't think it makes sense to have two notifier implementations in the kernel.
> > The original intention was to have the notifier deal with both CEC and ASoC
> > notifications, but there was not enough interest for the ASoC bits at the time
> > and it was dropped.
> >
> > I am planning changes to the cec-notifier API, I hope to work on that this
> > week. I'll CC you when I post those. Those might be a good starting point
> > to convert the cec-notifier to an hdmi-notifier as was originally intended.
> >
> > I've added your colleague Dariusz Marcinkiewicz to the CC list since he's been
> > working on some nice cec-notifier improvements as well.
>
> We also have some interfaces for drm/alsa interactions around hdmi
> already in drm/drm_audio_component.h, but it's not used by anything
> outside of i915. Imo we should extend that, not reinvent a new wheel.
>
Hi Daniel,
Thank you for the pointer. Looking at the ops, it seems that it is
specific to HDA.
I am not familiar with drm and HDA. I am not sure how applicable it
would be to report jack status to ASoC.
There is a use case in sound/soc/codecs/hdac_hdmi.c though so it
should be possible.

> Another note: notifiers considered evil, imo. Gets the job done for one
> case, as soon as you have multiple devices and need to make sure you get
> the update for the right one it all comes crashing down. Please create an
> api which registers for updates from a specific device only, plus
> something that has real callbacks (like the drm_audio_component.h thing we
> started already).

To clarify a bit, this hdmi-notifier indeed supports updating from a
specific device only.
hdmi_notifier_get takes a device and return the notifier.

It seems that a major difference between drm_audio_components and
hdmi-notifier is that
drm_audio_components defines all supported ops in drm_audio_component_audio_ops.
On the other hand, hdmi-notifier passes different events using an enum
like HDMI_CONNECTED and let listener handle different events.
In this regard I agree with you that drm_audio_component is cleaner.
Anyway, I will look into it a bit more and see how it works.

Thanks again!

> -Daniel
>
> >
> > Regards,
> >
> > Hans
> >
> > >
> > > Modified by Cheng-Yi Chiang:
> > > - Add a section in MAINTAINER.
> > > - Changes connected and has_eld to bitfield of unsigned int.
> > > - Other minor fixes to pass checkpatch.pl --strict checks.
> > >
> > > Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> > > Acked-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
> > > Signed-off-by: Cheng-Yi Chiang <cychiang@xxxxxxxxxxxx>
> > > ---
> > > The original patch is at
> > > https://lore.kernel.org/linux-arm-kernel/20161213150813.37966-2-hverkuil@xxxxxxxxx
> > >
> > > MAINTAINERS | 6 ++
> > > drivers/video/Kconfig | 3 +
> > > drivers/video/Makefile | 1 +
> > > drivers/video/hdmi-notifier.c | 145 ++++++++++++++++++++++++++++++++++
> > > include/linux/hdmi-notifier.h | 112 ++++++++++++++++++++++++++
> > > 5 files changed, 267 insertions(+)
> > > create mode 100644 drivers/video/hdmi-notifier.c
> > > create mode 100644 include/linux/hdmi-notifier.h
> > >
> > > diff --git a/MAINTAINERS b/MAINTAINERS
> > > index 5cfbea4ce575..ffb7376f9509 100644
> > > --- a/MAINTAINERS
> > > +++ b/MAINTAINERS
> > > @@ -16676,6 +16676,12 @@ W: https://linuxtv.org
> > > S: Maintained
> > > F: drivers/media/platform/vicodec/*
> > >
> > > +VIDEO FRAMEWORK
> > > +M: Hans Verkuil <hverkuil@xxxxxxxxx>
> > > +L: linux-media@xxxxxxxxxxxxxxx
> > > +F: drivers/video/hdmi-notifier.*
> > > +S: Maintained
> > > +
> > > VIDEO MULTIPLEXER DRIVER
> > > M: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
> > > L: linux-media@xxxxxxxxxxxxxxx
> > > diff --git a/drivers/video/Kconfig b/drivers/video/Kconfig
> > > index 83d3d271ca15..000ba9bc0ae7 100644
> > > --- a/drivers/video/Kconfig
> > > +++ b/drivers/video/Kconfig
> > > @@ -34,6 +34,9 @@ config VIDEOMODE_HELPERS
> > > config HDMI
> > > bool
> > >
> > > +config HDMI_NOTIFIERS
> > > + bool
> > > +
> > > endif # HAS_IOMEM
> > >
> > > if VT
> > > diff --git a/drivers/video/Makefile b/drivers/video/Makefile
> > > index df7650adede9..eff4736102ca 100644
> > > --- a/drivers/video/Makefile
> > > +++ b/drivers/video/Makefile
> > > @@ -1,6 +1,7 @@
> > > # SPDX-License-Identifier: GPL-2.0
> > > obj-$(CONFIG_VGASTATE) += vgastate.o
> > > obj-$(CONFIG_HDMI) += hdmi.o
> > > +obj-$(CONFIG_HDMI_NOTIFIERS) += hdmi-notifier.o
> > >
> > > obj-$(CONFIG_VT) += console/
> > > obj-$(CONFIG_FB_STI) += console/
> > > diff --git a/drivers/video/hdmi-notifier.c b/drivers/video/hdmi-notifier.c
> > > new file mode 100644
> > > index 000000000000..d1eedf661648
> > > --- /dev/null
> > > +++ b/drivers/video/hdmi-notifier.c
> > > @@ -0,0 +1,145 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/* hdmi-notifier.c - notify interested parties of (dis)connect and EDID
> > > + * events
> > > + *
> > > + * Copyright 2016 Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
> > > + * Copyright 2016 Cisco Systems, Inc. and/or its affiliates.
> > > + * All rights reserved.
> > > + */
> > > +
> > > +#include <linux/export.h>
> > > +#include <linux/hdmi-notifier.h>
> > > +#include <linux/string.h>
> > > +#include <linux/slab.h>
> > > +#include <linux/list.h>
> > > +
> > > +static LIST_HEAD(hdmi_notifiers);
> > > +static DEFINE_MUTEX(hdmi_notifiers_lock);
> > > +
> > > +struct hdmi_notifier *hdmi_notifier_get(struct device *dev)
> > > +{
> > > + struct hdmi_notifier *n;
> > > +
> > > + mutex_lock(&hdmi_notifiers_lock);
> > > + list_for_each_entry(n, &hdmi_notifiers, head) {
> > > + if (n->dev == dev) {
> > > + mutex_unlock(&hdmi_notifiers_lock);
> > > + kref_get(&n->kref);
> > > + return n;
> > > + }
> > > + }
> > > + n = kzalloc(sizeof(*n), GFP_KERNEL);
> > > + if (!n)
> > > + goto unlock;
> > > + n->dev = dev;
> > > + mutex_init(&n->lock);
> > > + BLOCKING_INIT_NOTIFIER_HEAD(&n->notifiers);
> > > + kref_init(&n->kref);
> > > + list_add_tail(&n->head, &hdmi_notifiers);
> > > +unlock:
> > > + mutex_unlock(&hdmi_notifiers_lock);
> > > + return n;
> > > +}
> > > +EXPORT_SYMBOL_GPL(hdmi_notifier_get);
> > > +
> > > +static void hdmi_notifier_release(struct kref *kref)
> > > +{
> > > + struct hdmi_notifier *n =
> > > + container_of(kref, struct hdmi_notifier, kref);
> > > +
> > > + mutex_lock(&hdmi_notifiers_lock);
> > > + list_del(&n->head);
> > > + mutex_unlock(&hdmi_notifiers_lock);
> > > + kfree(n->edid);
> > > + kfree(n);
> > > +}
> > > +
> > > +void hdmi_notifier_put(struct hdmi_notifier *n)
> > > +{
> > > + kref_put(&n->kref, hdmi_notifier_release);
> > > +}
> > > +EXPORT_SYMBOL_GPL(hdmi_notifier_put);
> > > +
> > > +int hdmi_notifier_register(struct hdmi_notifier *n, struct notifier_block *nb)
> > > +{
> > > + int ret = blocking_notifier_chain_register(&n->notifiers, nb);
> > > +
> > > + if (ret)
> > > + return ret;
> > > + kref_get(&n->kref);
> > > + mutex_lock(&n->lock);
> > > + if (n->connected) {
> > > + blocking_notifier_call_chain(&n->notifiers, HDMI_CONNECTED, n);
> > > + if (n->edid_size)
> > > + blocking_notifier_call_chain(&n->notifiers,
> > > + HDMI_NEW_EDID, n);
> > > + if (n->has_eld)
> > > + blocking_notifier_call_chain(&n->notifiers,
> > > + HDMI_NEW_ELD, n);
> > > + }
> > > + mutex_unlock(&n->lock);
> > > + return 0;
> > > +}
> > > +EXPORT_SYMBOL_GPL(hdmi_notifier_register);
> > > +
> > > +int hdmi_notifier_unregister(struct hdmi_notifier *n, struct notifier_block *nb)
> > > +{
> > > + int ret = blocking_notifier_chain_unregister(&n->notifiers, nb);
> > > +
> > > + if (ret == 0)
> > > + hdmi_notifier_put(n);
> > > + return ret;
> > > +}
> > > +EXPORT_SYMBOL_GPL(hdmi_notifier_unregister);
> > > +
> > > +void hdmi_event_connect(struct hdmi_notifier *n)
> > > +{
> > > + mutex_lock(&n->lock);
> > > + n->connected = true;
> > > + blocking_notifier_call_chain(&n->notifiers, HDMI_CONNECTED, n);
> > > + mutex_unlock(&n->lock);
> > > +}
> > > +EXPORT_SYMBOL_GPL(hdmi_event_connect);
> > > +
> > > +void hdmi_event_disconnect(struct hdmi_notifier *n)
> > > +{
> > > + mutex_lock(&n->lock);
> > > + n->connected = false;
> > > + n->has_eld = false;
> > > + n->edid_size = 0;
> > > + blocking_notifier_call_chain(&n->notifiers, HDMI_DISCONNECTED, n);
> > > + mutex_unlock(&n->lock);
> > > +}
> > > +EXPORT_SYMBOL_GPL(hdmi_event_disconnect);
> > > +
> > > +int hdmi_event_new_edid(struct hdmi_notifier *n, const void *edid, size_t size)
> > > +{
> > > + mutex_lock(&n->lock);
> > > + if (n->edid_allocated_size < size) {
> > > + void *p = kmalloc(size, GFP_KERNEL);
> > > +
> > > + if (!p) {
> > > + mutex_unlock(&n->lock);
> > > + return -ENOMEM;
> > > + }
> > > + kfree(n->edid);
> > > + n->edid = p;
> > > + n->edid_allocated_size = size;
> > > + }
> > > + memcpy(n->edid, edid, size);
> > > + n->edid_size = size;
> > > + blocking_notifier_call_chain(&n->notifiers, HDMI_NEW_EDID, n);
> > > + mutex_unlock(&n->lock);
> > > + return 0;
> > > +}
> > > +EXPORT_SYMBOL_GPL(hdmi_event_new_edid);
> > > +
> > > +void hdmi_event_new_eld(struct hdmi_notifier *n, const u8 eld[128])
> > > +{
> > > + mutex_lock(&n->lock);
> > > + memcpy(n->eld, eld, sizeof(n->eld));
> > > + n->has_eld = true;
> > > + blocking_notifier_call_chain(&n->notifiers, HDMI_NEW_ELD, n);
> > > + mutex_unlock(&n->lock);
> > > +}
> > > +EXPORT_SYMBOL_GPL(hdmi_event_new_eld);
> > > diff --git a/include/linux/hdmi-notifier.h b/include/linux/hdmi-notifier.h
> > > new file mode 100644
> > > index 000000000000..c8f35110e3e3
> > > --- /dev/null
> > > +++ b/include/linux/hdmi-notifier.h
> > > @@ -0,0 +1,112 @@
> > > +/* SPDX-License-Identifier: GPL-2.0
> > > + * hdmi-notifier.h - notify interested parties of (dis)connect and EDID
> > > + * events
> > > + *
> > > + * Copyright 2016 Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
> > > + * Copyright 2016 Cisco Systems, Inc. and/or its affiliates.
> > > + * All rights reserved.
> > > + */
> > > +
> > > +#ifndef LINUX_HDMI_NOTIFIER_H
> > > +#define LINUX_HDMI_NOTIFIER_H
> > > +
> > > +#include <linux/types.h>
> > > +#include <linux/notifier.h>
> > > +#include <linux/kref.h>
> > > +
> > > +enum {
> > > + HDMI_CONNECTED,
> > > + HDMI_DISCONNECTED,
> > > + HDMI_NEW_EDID,
> > > + HDMI_NEW_ELD,
> > > +};
> > > +
> > > +struct device;
> > > +
> > > +struct hdmi_notifier {
> > > + /* Lock to protect callback registration and notification. */
> > > + struct mutex lock;
> > > + struct list_head head;
> > > + struct kref kref;
> > > + struct blocking_notifier_head notifiers;
> > > + struct device *dev;
> > > +
> > > + /* Current state */
> > > + unsigned int connected : 1;
> > > + unsigned int has_eld : 1;
> > > + unsigned char eld[128];
> > > + void *edid;
> > > + size_t edid_size;
> > > + size_t edid_allocated_size;
> > > +};
> > > +
> > > +/**
> > > + * hdmi_notifier_get - find or create a new hdmi_notifier for the given device.
> > > + * @dev: device that sends the events.
> > > + *
> > > + * If a notifier for device @dev already exists, then increase the refcount
> > > + * and return that notifier.
> > > + *
> > > + * If it doesn't exist, then allocate a new notifier struct and return a
> > > + * pointer to that new struct.
> > > + *
> > > + * Return NULL if the memory could not be allocated.
> > > + */
> > > +struct hdmi_notifier *hdmi_notifier_get(struct device *dev);
> > > +
> > > +/**
> > > + * hdmi_notifier_put - decrease refcount and delete when the refcount reaches 0.
> > > + * @n: notifier
> > > + */
> > > +void hdmi_notifier_put(struct hdmi_notifier *n);
> > > +
> > > +/**
> > > + * hdmi_notifier_register - register the notifier with the notifier_block.
> > > + * @n: the HDMI notifier
> > > + * @nb: the notifier_block
> > > + */
> > > +int hdmi_notifier_register(struct hdmi_notifier *n, struct notifier_block *nb);
> > > +
> > > +/**
> > > + * hdmi_notifier_unregister - unregister the notifier with the notifier_block.
> > > + * @n: the HDMI notifier
> > > + * @nb: the notifier_block
> > > + */
> > > +int hdmi_notifier_unregister(struct hdmi_notifier *n,
> > > + struct notifier_block *nb);
> > > +
> > > +/**
> > > + * hdmi_event_connect - send a connect event.
> > > + * @n: the HDMI notifier
> > > + *
> > > + * Send an HDMI_CONNECTED event to any registered parties.
> > > + */
> > > +void hdmi_event_connect(struct hdmi_notifier *n);
> > > +
> > > +/**
> > > + * hdmi_event_disconnect - send a disconnect event.
> > > + * @n: the HDMI notifier
> > > + *
> > > + * Send an HDMI_DISCONNECTED event to any registered parties.
> > > + */
> > > +void hdmi_event_disconnect(struct hdmi_notifier *n);
> > > +
> > > +/**
> > > + * hdmi_event_new_edid - send a new EDID event.
> > > + * @n: the HDMI notifier
> > > + *
> > > + * Send an HDMI_NEW_EDID event to any registered parties.
> > > + * This function will make a copy the EDID so it can return -ENOMEM if
> > > + * no memory could be allocated.
> > > + */
> > > +int hdmi_event_new_edid(struct hdmi_notifier *n, const void *edid, size_t size);
> > > +
> > > +/**
> > > + * hdmi_event_new_eld - send a new ELD event.
> > > + * @n: the HDMI notifier
> > > + *
> > > + * Send an HDMI_NEW_ELD event to any registered parties.
> > > + */
> > > +void hdmi_event_new_eld(struct hdmi_notifier *n, const u8 eld[128]);
> > > +
> > > +#endif
> > >
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

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In reply to: Daniel Vetter: "Re: [PATCH 1/7] video: add HDMI state notifier support"
Next in thread: Daniel Vetter: "Re: [PATCH 1/7] video: add HDMI state notifier support"
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