From: Hans Verkuil <hverkuil@xs4all.nl>
To: Shuah Khan <shuahkh@osg.samsung.com>,
mchehab@osg.samsung.com, laurent.pinchart@ideasonboard.com,
sakari.ailus@iki.fi, hans.verkuil@cisco.com,
chehabrafael@gmail.com, javier@osg.samsung.com,
inki.dae@samsung.com, g.liakhovetski@gmx.de,
jh1009.sung@samsung.com
Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] media: Media Device Allocator API
Date: Fri, 27 May 2016 15:26:41 +0200 [thread overview]
Message-ID: <57484B11.2060400@xs4all.nl> (raw)
In-Reply-To: <90f39ad8de612214e52d7be35be3077b7510786a.1464132578.git.shuahkh@osg.samsung.com>
On 05/25/2016 01:39 AM, Shuah Khan wrote:
> Media Device Allocator API to allows multiple drivers share a media device.
> Using this API, drivers can allocate a media device with the shared struct
> device as the key. Once the media device is allocated by a driver, other
> drivers can get a reference to it. The media device is released when all
> the references are released.
>
> Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
> ---
> drivers/media/Makefile | 3 +-
> drivers/media/media-dev-allocator.c | 120 ++++++++++++++++++++++++++++++++++++
> include/media/media-dev-allocator.h | 85 +++++++++++++++++++++++++
> 3 files changed, 207 insertions(+), 1 deletion(-)
> create mode 100644 drivers/media/media-dev-allocator.c
> create mode 100644 include/media/media-dev-allocator.h
>
> diff --git a/drivers/media/Makefile b/drivers/media/Makefile
> index e608bbc..b08f091 100644
> --- a/drivers/media/Makefile
> +++ b/drivers/media/Makefile
> @@ -2,7 +2,8 @@
> # Makefile for the kernel multimedia device drivers.
> #
>
> -media-objs := media-device.o media-devnode.o media-entity.o
> +media-objs := media-device.o media-devnode.o media-entity.o \
> + media-dev-allocator.o
>
> #
> # I2C drivers should come before other drivers, otherwise they'll fail
> diff --git a/drivers/media/media-dev-allocator.c b/drivers/media/media-dev-allocator.c
> new file mode 100644
> index 0000000..b8c9811
> --- /dev/null
> +++ b/drivers/media/media-dev-allocator.c
> @@ -0,0 +1,120 @@
> +/*
> + * media-dev-allocator.c - Media Controller Device Allocator API
> + *
> + * Copyright (c) 2016 Shuah Khan <shuahkh@osg.samsung.com>
> + * Copyright (c) 2016 Samsung Electronics Co., Ltd.
> + *
> + * This file is released under the GPLv2.
> + * Credits: Suggested by Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> + */
> +
> +/*
> + * This file adds a global refcounted Media Controller Device Instance API.
> + * A system wide global media device list is managed and each media device
> + * includes a kref count. The last put on the media device releases the media
> + * device instance.
> + *
> +*/
> +
> +#include <linux/slab.h>
> +#include <linux/kref.h>
> +#include <linux/usb.h>
> +#include <media/media-device.h>
> +
> +static LIST_HEAD(media_device_list);
> +static DEFINE_MUTEX(media_device_lock);
> +
> +struct media_device_instance {
> + struct media_device mdev;
> + struct list_head list;
> + struct device *dev;
> + struct kref refcount;
> +};
> +
> +static inline struct media_device_instance *
> +to_media_device_instance(struct media_device *mdev)
> +{
> + return container_of(mdev, struct media_device_instance, mdev);
> +}
> +
> +static void media_device_instance_release(struct kref *kref)
> +{
> + struct media_device_instance *mdi =
> + container_of(kref, struct media_device_instance, refcount);
> +
> + dev_dbg(mdi->mdev.dev, "%s: mdev=%p\n", __func__, &mdi->mdev);
> +
> + mutex_lock(&media_device_lock);
> +
> + media_device_unregister(&mdi->mdev);
> + media_device_cleanup(&mdi->mdev);
> +
> + list_del(&mdi->list);
> + mutex_unlock(&media_device_lock);
> +
> + kfree(mdi);
> +}
> +
Add a comment here saying that media_device_lock has to be locked when
calling this get function.
> +static struct media_device *__media_device_get(struct device *dev,
> + bool allocate)
I think you can just drop the allocate argument: you're always allocating if
the media_device wasn't found.
> +{
> + struct media_device_instance *mdi;
> +
> + list_for_each_entry(mdi, &media_device_list, list) {
> + if (mdi->dev == dev) {
> + kref_get(&mdi->refcount);
> + dev_dbg(dev, "%s: get mdev=%p\n",
> + __func__, &mdi->mdev);
> + goto done;
Just say 'return &mdi->mdev;', no goto needed.
> + }
> + }
> +
> + if (!allocate) {
> + mdi = NULL;
> + goto done;
> + }
> +
> + mdi = kzalloc(sizeof(*mdi), GFP_KERNEL);
> + if (!mdi)
> + goto done;
Same here, just do 'return NULL;'
> +
> + mdi->dev = dev;
> + kref_init(&mdi->refcount);
> + list_add_tail(&mdi->list, &media_device_list);
> +
> + dev_dbg(dev, "%s: alloc mdev=%p\n", __func__, &mdi->mdev);
> +done:
> + return mdi ? &mdi->mdev : NULL;
> +}
> +
> +struct media_device *media_device_usb_allocate(struct usb_device *udev,
> + char *driver_name)
> +{
> + struct media_device *mdev;
> +
> + mutex_lock(&media_device_lock);
> + mdev = __media_device_get(&udev->dev, true);
> + if (!mdev) {
> + mutex_unlock(&media_device_lock);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + /* check if media device is already initialized */
> + if (!mdev->dev)
> + __media_device_usb_init(mdev, udev, udev->product,
> + driver_name);
> + mutex_unlock(&media_device_lock);
> +
> + dev_dbg(&udev->dev, "%s\n", __func__);
> + return mdev;
> +}
> +EXPORT_SYMBOL_GPL(media_device_usb_allocate);
> +
> +void media_device_delete(struct media_device *mdev)
> +{
> + struct media_device_instance *mdi = to_media_device_instance(mdev);
> +
> + dev_dbg(mdi->mdev.dev, "%s: mdev=%p\n", __func__, &mdi->mdev);
> + kref_put(&mdi->refcount, media_device_instance_release);
> +}
> +EXPORT_SYMBOL_GPL(media_device_delete);
> diff --git a/include/media/media-dev-allocator.h b/include/media/media-dev-allocator.h
> new file mode 100644
> index 0000000..fda032b
> --- /dev/null
> +++ b/include/media/media-dev-allocator.h
> @@ -0,0 +1,85 @@
> +/*
> + * media-dev-allocator.h - Media Controller Device Allocator API
> + *
> + * Copyright (c) 2016 Shuah Khan <shuahkh@osg.samsung.com>
> + * Copyright (c) 2016 Samsung Electronics Co., Ltd.
> + *
> + * This file is released under the GPLv2.
> + * Credits: Suggested by Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> + */
> +
> +/*
> + * This file adds a global ref-counted Media Controller Device Instance API.
> + * A system wide global media device list is managed and each media device
> + * includes a kref count. The last put on the media device releases the media
> + * device instance.
> +*/
> +
> +#ifndef _MEDIA_DEV_ALLOCTOR_H
> +#define _MEDIA_DEV_ALLOCTOR_H
> +
> +struct usb_device;
> +
> +#ifdef CONFIG_MEDIA_CONTROLLER
> +/**
> + * DOC: Media Controller Device Allocator API
> + *
> + * When media device belongs to more than one driver, the shared media device
> + * is allocated with the shared struct device as the key for look ups.
> + *
> + * Shared media device should stay in registered state until the last driver
> + * unregisters it. In addition, media device should be released when all the
> + * references are released. Each driver gets a reference to the media device
> + * during probe, when it allocates the media device. If media device is already
> + * allocated, allocate API bumps up the refcount and return the existing media
> + * device. Driver puts the reference back from its disconnect routine when it
> + * calls media_device_delete().
> + *
> + * Media device is unregistered and cleaned up from the kref put handler to
> + * ensure that the media device stays in registered state until the last driver
> + * unregisters the media device.
> + *
> + * Driver Usage:
> + *
> + * Drivers should use the media-core routines to get register reference and
> + * call media_device_delete() routine to make sure the shared media device
> + * delete is handled correctly.
> + *
> + * driver probe:
> + * Call media_device_usb_allocate() to allocate or get a reference
> + * Call media_device_register(), if media devnode isn't registered
> + *
> + * driver disconnect:
> + * Call media_device_delete() to free the media_device. Free'ing is
> + * handled by the put handler.
> + *
> + */
> +
> +/**
> + * media_device_usb_allocate() - Allocate and return media device
> + *
> + * @udev - struct usb_device pointer
> + * @driver_name
> + *
> + * This interface should be called to allocate a media device when multiple
> + * drivers share usb_device and the media device. This interface allocates
> + * media device and calls media_device_usb_init() to initialize it.
> + *
> + */
> +struct media_device *media_device_usb_allocate(struct usb_device *udev,
> + char *driver_name);
> +/**
> + * media_device_delete() - Release media device. Calls kref_put().
> + *
> + * @mdev - struct media_device pointer
> + *
> + * This interface should be called to put Media Device Instance kref.
> + */
> +void media_device_delete(struct media_device *mdev);
> +#else
> +static inline struct media_device *media_device_usb_allocate(
> + struct usb_device *udev, char *driver_name)
> + { return NULL; }
> +static inline void media_device_delete(struct media_device *mdev) { }
> +#endif /* CONFIG_MEDIA_CONTROLLER */
> +#endif
>
Regards,
Hans
next prev parent reply other threads:[~2016-05-27 13:26 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-24 23:39 [PATCH v2 0/2] Media Device Allocator API Shuah Khan
2016-05-24 23:39 ` [PATCH v2 1/2] media: " Shuah Khan
2016-05-27 13:26 ` Hans Verkuil [this message]
2016-05-27 20:44 ` Shuah Khan
2016-05-24 23:39 ` [PATCH v2 2/2] media: change au0828 to use " Shuah Khan
2016-06-28 19:56 ` [PATCH v2 0/2] " Shuah Khan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=57484B11.2060400@xs4all.nl \
--to=hverkuil@xs4all.nl \
--cc=chehabrafael@gmail.com \
--cc=g.liakhovetski@gmx.de \
--cc=hans.verkuil@cisco.com \
--cc=inki.dae@samsung.com \
--cc=javier@osg.samsung.com \
--cc=jh1009.sung@samsung.com \
--cc=laurent.pinchart@ideasonboard.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=mchehab@osg.samsung.com \
--cc=sakari.ailus@iki.fi \
--cc=shuahkh@osg.samsung.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).