Hi Guennadi,
On 04/12/2013 05:40 PM, Guennadi Liakhovetski wrote:
> Currently bridge device drivers register devices for all subdevices
> synchronously, tupically, during their probing. E.g. if an I2C CMOS sensor
> is attached to a video bridge device, the bridge driver will create an I2C
> device and wait for the respective I2C driver to probe. This makes linking
> of devices straight forward, but this approach cannot be used with
> intrinsically asynchronous and unordered device registration systems like
> the Flattened Device Tree. To support such systems this patch adds an
> asynchronous subdevice registration framework to V4L2. To use it respective
> (e.g. I2C) subdevice drivers must register themselves with the framework.
> A bridge driver on the other hand must register notification callbacks,
> that will be called upon various related events.
>
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
> ---
>
> v9: addressed Laurent's comments (thanks)
> 1. moved valid hw->bus_type check
> 2. made v4l2_async_unregister() void
> 3. renamed struct v4l2_async_hw_device to struct v4l2_async_hw_info
> 4. merged struct v4l2_async_subdev_list into struct v4l2_subdev
> 5. fixed a typo
> 6. made subdev_num unsigned
>
> drivers/media/v4l2-core/Makefile | 3 +-
> drivers/media/v4l2-core/v4l2-async.c | 284 ++++++++++++++++++++++++++++++++++
> include/media/v4l2-async.h | 99 ++++++++++++
> include/media/v4l2-subdev.h | 10 ++
> 4 files changed, 395 insertions(+), 1 deletions(-)
> create mode 100644 drivers/media/v4l2-core/v4l2-async.c
> create mode 100644 include/media/v4l2-async.h
>
> diff --git a/drivers/media/v4l2-core/Makefile b/drivers/media/v4l2-core/Makefile
> index 628c630..4c33b8d6 100644
> --- a/drivers/media/v4l2-core/Makefile
> +++ b/drivers/media/v4l2-core/Makefile
> @@ -5,7 +5,8 @@
> tuner-objs := tuner-core.o
>
> videodev-objs := v4l2-dev.o v4l2-ioctl.o v4l2-device.o v4l2-fh.o \
> - v4l2-event.o v4l2-ctrls.o v4l2-subdev.o v4l2-clk.o
> + v4l2-event.o v4l2-ctrls.o v4l2-subdev.o v4l2-clk.o \
> + v4l2-async.o
> ifeq ($(CONFIG_COMPAT),y)
> videodev-objs += v4l2-compat-ioctl32.o
> endif
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> new file mode 100644
> index 0000000..98db2e0
> --- /dev/null
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -0,0 +1,284 @@
> +/*
> + * V4L2 asynchronous subdevice registration API
> + *
> + * Copyright (C) 2012-2013, Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
[...]
> +static void v4l2_async_cleanup(struct v4l2_async_subdev_list *asdl)
> +{
> + struct v4l2_subdev *sd = v4l2_async_to_subdev(asdl);
> +
> + v4l2_device_unregister_subdev(sd);
> + /* Subdevice driver will reprobe and put asdl back onto the list */
> + list_del_init(&asdl->list);
> + asdl->asd = NULL;
> + sd->dev = NULL;
> +}
> +
> +static void v4l2_async_unregister(struct v4l2_async_subdev_list *asdl)
> +{
> + struct v4l2_subdev *sd = v4l2_async_to_subdev(asdl);
> +
> + v4l2_async_cleanup(asdl);
> +
> + /* If we handled USB devices, we'd have to lock the parent too */
> + device_release_driver(sd->dev);
> +}
> +
> +int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
> + struct v4l2_async_notifier *notifier)
> +{
> + struct v4l2_async_subdev_list *asdl, *tmp;
> + struct v4l2_async_subdev *asd;
> + int i;
> +
> + notifier->v4l2_dev = v4l2_dev;
> + INIT_LIST_HEAD(¬ifier->waiting);
> + INIT_LIST_HEAD(¬ifier->done);
> +
> + for (i = 0; i < notifier->subdev_num; i++) {
> + asd = notifier->subdev[i];
> +
> + switch (asd->hw.bus_type) {
> + case V4L2_ASYNC_BUS_CUSTOM:
> + case V4L2_ASYNC_BUS_PLATFORM:
> + case V4L2_ASYNC_BUS_I2C:
> + break;
> + default:
> + dev_err(notifier->v4l2_dev ? notifier->v4l2_dev->dev : NULL,
> + "Invalid bus-type %u on %p\n",
> + asd->hw.bus_type, asd);
> + return -EINVAL;
> + }
> + list_add_tail(&asd->list, ¬ifier->waiting);
> + }
> +
> + mutex_lock(&list_lock);
> +
> + /* Keep also completed notifiers on the list */
> + list_add(¬ifier->list, ¬ifier_list);
> +
> + list_for_each_entry_safe(asdl, tmp, &subdev_list, list) {
> + int ret;
> +
> + asd = v4l2_async_belongs(notifier, asdl);
> + if (!asd)
> + continue;
> +
> + ret = v4l2_async_test_notify(notifier, asdl, asd);
> + if (ret < 0) {
> + mutex_unlock(&list_lock);
> + return ret;
> + }
> + }
> +
> + mutex_unlock(&list_lock);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(v4l2_async_notifier_register);
> +
> +void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
> +{
> + struct v4l2_async_subdev_list *asdl, *tmp;
> + int i = 0;
> + struct device **dev = kcalloc(notifier->subdev_num,
> + sizeof(*dev), GFP_KERNEL);
> + if (!dev)
> + dev_err(notifier->v4l2_dev->dev,
> + "Failed to allocate device cache!\n");
> +
> + mutex_lock(&list_lock);
> +
> + list_del(¬ifier->list);
> +
> + list_for_each_entry_safe(asdl, tmp, ¬ifier->done, list) {
> + if (dev) {
> + struct v4l2_subdev *sd = v4l2_async_to_subdev(asdl);
> + dev[i++] = get_device(sd->dev);
> + }
> + v4l2_async_unregister(asdl);
Hmm, couldn't we do without the **dev array ? Now when struct v42_subdev has
struct device * embedded in it ?
And if we can't get hold off struct device object is it safe to call
v4l2_async_unregister(), which references it ?
Why is get_device() optional ? Some comment might be useful here.
> +
> + if (notifier->unbind)
> + notifier->unbind(notifier, asdl);
> + }
> +
> + mutex_unlock(&list_lock);
> +
> + if (dev) {
> + while (i--) {
> + if (dev[i] && device_attach(dev[i]) < 0)
> + dev_err(dev[i], "Failed to re-probe to %s\n",
> + dev[i]->driver ? dev[i]->driver->name : "(none)");
Is it safe to reference dev->driver without holding struct device::mutex ?
> + put_device(dev[i]);
> + }
> + kfree(dev);
> + }
> + /*
> + * Don't care about the waiting list, it is initialised and populated
> + * upon notifier registration.
> + */
> +}
> +EXPORT_SYMBOL(v4l2_async_notifier_unregister);
> +
> +int v4l2_async_register_subdev(struct v4l2_subdev *sd)
> +{
> + struct v4l2_async_subdev_list *asdl = &sd->asdl;
> + struct v4l2_async_notifier *notifier;
> +
> + mutex_lock(&list_lock);
> +
> + INIT_LIST_HEAD(&asdl->list);
> +
> + list_for_each_entry(notifier, ¬ifier_list, list) {
> + struct v4l2_async_subdev *asd = v4l2_async_belongs(notifier, asdl);
> + if (asd) {
> + int ret = v4l2_async_test_notify(notifier, asdl, asd);
> + mutex_unlock(&list_lock);
> + return ret;
> + }
> + }
> +
> + /* None matched, wait for hot-plugging */
> + list_add(&asdl->list, &subdev_list);
> +
> + mutex_unlock(&list_lock);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(v4l2_async_register_subdev);
> +
> +void v4l2_async_unregister_subdev(struct v4l2_subdev *sd)
> +{
> + struct v4l2_async_subdev_list *asdl = &sd->asdl;
> + struct v4l2_async_notifier *notifier = asdl->notifier;
> + struct device *dev;
This variable appears unused, except a single assignment below.
> + if (!asdl->asd) {
> + if (!list_empty(&asdl->list))
> + v4l2_async_cleanup(asdl);
> + return;
> + }
> +
> + mutex_lock(&list_lock);
> +
> + dev = sd->dev;
> + list_add(&asdl->asd->list, ¬ifier->waiting);
> +
> + v4l2_async_cleanup(asdl);
> +
> + if (notifier->unbind)
> + notifier->unbind(notifier, asdl);
> +
> + mutex_unlock(&list_lock);
> +}
> +EXPORT_SYMBOL(v4l2_async_unregister_subdev);
> diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
> new file mode 100644
> index 0000000..c638f5c
> --- /dev/null
> +++ b/include/media/v4l2-async.h
> @@ -0,0 +1,99 @@
> +/*
> + * V4L2 asynchronous subdevice registration API
> + *
> + * Copyright (C) 2012-2013, Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#ifndef V4L2_ASYNC_H
> +#define V4L2_ASYNC_H
> +
> +#include <linux/list.h>
> +#include <linux/mutex.h>
> +
> +struct device;
> +struct v4l2_device;
> +struct v4l2_subdev;
> +struct v4l2_async_notifier;
> +
> +enum v4l2_async_bus_type {
> + V4L2_ASYNC_BUS_CUSTOM,
> + V4L2_ASYNC_BUS_PLATFORM,
> + V4L2_ASYNC_BUS_I2C,
> +};
> +
> +struct v4l2_async_hw_info {
> + enum v4l2_async_bus_type bus_type;
> + union {
> + struct {
> + const char *name;
> + } platform;
> + struct {
> + int adapter_id;
> + unsigned short address;
> + } i2c;
> + struct {
> + bool (*match)(struct device *,
> + struct v4l2_async_hw_info *);
> + void *priv;
> + } custom;
> + } match;
> +};
> +
> +/**
> + * struct v4l2_async_subdev - sub-device descriptor, as known to a bridge
> + * @hw: this device descriptor
> + * @list: member in a list of subdevices
> + */
> +struct v4l2_async_subdev {
> + struct v4l2_async_hw_info hw;
> + struct list_head list;
> +};
> +
> +/**
> + * v4l2_async_subdev_list - provided by subdevices
> + * @list: member in a list of subdevices
> + * @asd: pointer to respective struct v4l2_async_subdev
> + * @notifier: pointer to managing notifier
> + */
> +struct v4l2_async_subdev_list {
> + struct list_head list;
> + struct v4l2_async_subdev *asd;
> + struct v4l2_async_notifier *notifier;
> +};
> +
> +/**
> + * v4l2_async_notifier - provided by bridges
It probably makes sense to just say e.g.
v4l2_async_notifier - v4l2_device notifier data structure
I mean at least "bridge" to me doesn't sound generic enough.
> + * @subdev_num: number of subdevices
> + * @subdev: array of pointers to subdevices
> + * @v4l2_dev: pointer to struct v4l2_device
> + * @waiting: list of subdevices, waiting for their drivers
> + * @done: list of subdevices, already probed
> + * @list: member in a global list of notifiers
> + * @bound: a subdevice driver has successfully probed one of subdevices
> + * @complete: all subdevices have been probed successfully
> + * @unbind: a subdevice is leaving
> + */
> +struct v4l2_async_notifier {
> + unsigned int subdev_num;
> + struct v4l2_async_subdev **subdev;
> + struct v4l2_device *v4l2_dev;
> + struct list_head waiting;
> + struct list_head done;
> + struct list_head list;
> + int (*bound)(struct v4l2_async_notifier *notifier,
> + struct v4l2_async_subdev_list *asdl);
> + int (*complete)(struct v4l2_async_notifier *notifier);
> + void (*unbind)(struct v4l2_async_notifier *notifier,
> + struct v4l2_async_subdev_list *asdl);
I would preffer to simply pass struct v4l2_subdev * to bound/unbind.
Since it is about just one subdevice's status change, why do we need
struct v4l2_async_subdev_list ?
> +};
> +
> +int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
> + struct v4l2_async_notifier *notifier);
> +void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier);
How about naming it v4l2_device_notifier_(un)register() ?
> +int v4l2_async_register_subdev(struct v4l2_subdev *sd);
> +void v4l2_async_unregister_subdev(struct v4l2_subdev *sd);
Hopefully, one day it just becomes v4l2_(un)register_subdev() :-)
> +#endif
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index 5298d67..21174af 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -24,6 +24,7 @@
> #include <linux/types.h>
> #include <linux/v4l2-subdev.h>
> #include <media/media-entity.h>
> +#include <media/v4l2-async.h>
> #include <media/v4l2-common.h>
> #include <media/v4l2-dev.h>
> #include <media/v4l2-fh.h>
> @@ -585,8 +586,17 @@ struct v4l2_subdev {
> void *host_priv;
> /* subdev device node */
> struct video_device *devnode;
> + /* pointer to the physical device */
> + struct device *dev;
> + struct v4l2_async_subdev_list asdl;
Why not embed respective fields directly in struct v4l2_subdev, rather
than adding this new data structure ? I find this all code pretty much
convoluted, probably one of the reason is that there are multiple
list_head objects at various levels.
> };
>
> +static inline struct v4l2_subdev *v4l2_async_to_subdev(
> + struct v4l2_async_subdev_list *asdl)
> +{
> + return container_of(asdl, struct v4l2_subdev, asdl);
> +}
> +
> #define media_entity_to_v4l2_subdev(ent) \
> container_of(ent, struct v4l2_subdev, entity)
> #define vdev_to_v4l2_subdev(vdev) \
>
Thanks,
Sylwester
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