On 06/04/18 22:35, Sakari Ailus wrote:
> Hi Hans,
>
> Thanks for your work on this. A few comments below...
>
> On Wed, Mar 28, 2018 at 03:50:05PM +0200, Hans Verkuil wrote:
>> From: Hans Verkuil <hans.verkuil@xxxxxxxxx>
>>
>> Implement the core of the media request processing.
>>
>> Drivers can bind request objects to a request. These objects
>> can then be marked completed if the driver finished using them,
>> or just be unbound if the results do not need to be kept (e.g.
>> in the case of buffers).
>>
>> Once all objects that were added are either unbound or completed,
>> the request is marked 'complete' and a POLLPRI signal is sent
>> via poll.
>>
>> Both requests and request objects are refcounted.
>>
>> While a request is queued its refcount is incremented (since it
>> is in use by a driver). Once it is completed the refcount is
>> decremented. When the user closes the request file descriptor
>> the refcount is also decremented. Once it reaches 0 all request
>> objects in the request are unbound and put() and the request
>> itself is freed.
>>
>> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
>> ---
>> drivers/media/media-request.c | 269 +++++++++++++++++++++++++++++++++++++++++-
>> include/media/media-request.h | 148 +++++++++++++++++++++++
>> 2 files changed, 416 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/media/media-request.c b/drivers/media/media-request.c
>> index ead78613fdbe..8135d9d32af9 100644
>> --- a/drivers/media/media-request.c
>> +++ b/drivers/media/media-request.c
>> @@ -16,8 +16,275 @@
>> #include <media/media-device.h>
>> #include <media/media-request.h>
>>
>> +static const char * const request_state[] = {
>> + "idle",
>> + "queueing",
>> + "queued",
>> + "complete",
>> + "cleaning",
>> +};
>> +
>> +static const char *
>> +media_request_state_str(enum media_request_state state)
>> +{
>> + if (WARN_ON(state >= ARRAY_SIZE(request_state)))
>> + return "unknown";
>> + return request_state[state];
>> +}
>> +
>> +static void media_request_clean(struct media_request *req)
>> +{
>> + struct media_request_object *obj, *obj_safe;
>> +
>> + WARN_ON(req->state != MEDIA_REQUEST_STATE_CLEANING);
>> +
>> + list_for_each_entry_safe(obj, obj_safe, &req->objects, list) {
>> + media_request_object_unbind(obj);
>> + media_request_object_put(obj);
>> + }
>> +
>> + req->num_incomplete_objects = 0;
>> + wake_up_interruptible(&req->poll_wait);
>> +}
>> +
>> +static void media_request_release(struct kref *kref)
>> +{
>> + struct media_request *req =
>> + container_of(kref, struct media_request, kref);
>> + struct media_device *mdev = req->mdev;
>> + unsigned long flags;
>> +
>> + dev_dbg(mdev->dev, "request: release %s\n", req->debug_str);
>> +
>> + spin_lock_irqsave(&req->lock, flags);
>> + req->state = MEDIA_REQUEST_STATE_CLEANING;
>> + spin_unlock_irqrestore(&req->lock, flags);
>> +
>> + media_request_clean(req);
>> +
>> + if (mdev->ops->req_free)
>> + mdev->ops->req_free(req);
>> + else
>> + kfree(req);
>> +}
>> +
>> +void media_request_put(struct media_request *req)
>> +{
>> + kref_put(&req->kref, media_request_release);
>> +}
>> +EXPORT_SYMBOL_GPL(media_request_put);
>> +
>> +static int media_request_close(struct inode *inode, struct file *filp)
>> +{
>> + struct media_request *req = filp->private_data;
>> +
>> + media_request_put(req);
>
> One more newline?
>
>> + return 0;
>> +}
>> +
>> +static unsigned int media_request_poll(struct file *filp,
>> + struct poll_table_struct *wait)
>> +{
>> + struct media_request *req = filp->private_data;
>> + unsigned long flags;
>> + enum media_request_state state;
>> +
>> + if (!(poll_requested_events(wait) & POLLPRI))
>> + return 0;
>> +
>> + spin_lock_irqsave(&req->lock, flags);
>> + state = req->state;
>> + spin_unlock_irqrestore(&req->lock, flags);
>> +
>> + if (state == MEDIA_REQUEST_STATE_COMPLETE)
>> + return POLLPRI;
>> + if (state == MEDIA_REQUEST_STATE_IDLE)
>
> Should this be
>
> if (state != MEDIA_REQUEST_STATE_QUEUED)
Good question. I'll take another look at this.
>
> ? (Also see my other comment on the QUEUEING state below.)
>
>> + return POLLERR;
>> +
>> + poll_wait(filp, &req->poll_wait, wait);
>
> Newline?
>
>> + return 0;
>> +}
>> +
>> +static long media_request_ioctl(struct file *filp, unsigned int cmd,
>> + unsigned long __arg)
>> +{
>> + return -ENOIOCTLCMD;
>> +}
>> +
>> +static const struct file_operations request_fops = {
>> + .owner = THIS_MODULE,
>> + .poll = media_request_poll,
>> + .unlocked_ioctl = media_request_ioctl,
>> + .release = media_request_close,
>> +};
>> +
>> int media_request_alloc(struct media_device *mdev,
>> struct media_request_alloc *alloc)
>> {
>> - return -ENOMEM;
>> + struct media_request *req;
>> + struct file *filp;
>> + char comm[TASK_COMM_LEN];
>> + int fd;
>> + int ret;
>> +
>> + fd = get_unused_fd_flags(O_CLOEXEC);
>> + if (fd < 0)
>> + return fd;
>> +
>> + filp = anon_inode_getfile("request", &request_fops, NULL, O_CLOEXEC);
>> + if (IS_ERR(filp)) {
>> + ret = PTR_ERR(filp);
>> + goto err_put_fd;
>> + }
>> +
>> + if (mdev->ops->req_alloc)
>> + req = mdev->ops->req_alloc(mdev);
>> + else
>> + req = kzalloc(sizeof(*req), GFP_KERNEL);
>> + if (!req) {
>> + ret = -ENOMEM;
>> + goto err_fput;
>> + }
>> +
>> + filp->private_data = req;
>> + req->mdev = mdev;
>> + req->state = MEDIA_REQUEST_STATE_IDLE;
>> + req->num_incomplete_objects = 0;
>> + kref_init(&req->kref);
>> + INIT_LIST_HEAD(&req->objects);
>> + spin_lock_init(&req->lock);
>> + init_waitqueue_head(&req->poll_wait);
>> +
>> + alloc->fd = fd;
>> +
>> + get_task_comm(comm, current);
>> + snprintf(req->debug_str, sizeof(req->debug_str), "%s:%d",
>> + comm, fd);
>> + dev_dbg(mdev->dev, "request: allocated %s\n", req->debug_str);
>> +
>> + fd_install(fd, filp);
>> +
>> + return 0;
>> +
>> +err_fput:
>> + fput(filp);
>> +
>> +err_put_fd:
>> + put_unused_fd(fd);
>> +
>> + return ret;
>> +}
>> +
>> +static void media_request_object_release(struct kref *kref)
>> +{
>> + struct media_request_object *obj =
>> + container_of(kref, struct media_request_object, kref);
>> + struct media_request *req = obj->req;
>> +
>> + if (req)
>> + media_request_object_unbind(obj);
>
> Newline?
>
>> + obj->ops->release(obj);
>> +}
>> +
>> +void media_request_object_put(struct media_request_object *obj)
>> +{
>> + kref_put(&obj->kref, media_request_object_release);
>> +}
>> +EXPORT_SYMBOL_GPL(media_request_object_put);
>> +
>> +void media_request_object_init(struct media_request_object *obj)
>> +{
>> + obj->ops = NULL;
>> + obj->req = NULL;
>> + obj->priv = NULL;
>> + obj->completed = false;
>
> The function is intended to be used on a freshly allocated object only. The
> allocation function should already zero the memory, so there should be no
> need to do this here anymore.
Actually, that's not true. struct vb2_buffer contains struct media_request_object
but it is only allocated when you allocate the buffers, after that this has to
be initialized every time you queue or prepare a buffer for a request.
It's probably true for everything else though, but buffers are the exception.
>
>> + INIT_LIST_HEAD(&obj->list);
>
> There's no need to init this as it's a member of a list, not a head.
>
>> + kref_init(&obj->kref);
>> +}
>> +EXPORT_SYMBOL_GPL(media_request_object_init);
>> +
>> +void media_request_object_bind(struct media_request *req,
>> + const struct media_request_object_ops *ops,
>> + void *priv,
>> + struct media_request_object *obj)
>> +{
>> + unsigned long flags;
>> +
>> + WARN_ON(!ops->release);
>> + obj->req = req;
>> + obj->ops = ops;
>> + obj->priv = priv;
>> + spin_lock_irqsave(&req->lock, flags);
>> + if (WARN_ON(req->state != MEDIA_REQUEST_STATE_IDLE))
>
> How do you find out that a request is not in an idle state? I'd say you
> can't be sure otherwise as a request may be queued whilst another process
> is binding an object to it. I think the check here should be used prevent
> that.
??? If a request is being queued then the state is QUEUEING and you cannot
bind this object due to the test above. That's also the reason for having the
QUEUEING state: to prevent binding an object to a request that is in the
process of being queued.
>
> I'd also assign fields other than req in object init as objects may be
> unbound from requests and outlive requests (video buffers, for instance).
> No ops nor priv field may be changed during a lifetime of an object.
Sorry, no idea what you mean. Could it be that you want to move the ops and
priv arguments to the object_init() function instead of the bind()?
If that's the case, then I'll have to look at that. I think I did that at
one point in time, but I moved it to the bind for some reason.
>
>> + goto unlock;
>> + list_add_tail(&obj->list, &req->objects);
>> + req->num_incomplete_objects++;
>> +unlock:
>> + spin_unlock_irqrestore(&req->lock, flags);
>> +}
>> +EXPORT_SYMBOL_GPL(media_request_object_bind);
>> +
>> +void media_request_object_unbind(struct media_request_object *obj)
>> +{
>> + struct media_request *req = obj->req;
>> + unsigned long flags;
>> + bool completed = false;
>> +
>> + if (!req)
>> + return;
>> +
>> + spin_lock_irqsave(&req->lock, flags);
>> + list_del(&obj->list);
>> + obj->req = NULL;
>> +
>> + if (req->state == MEDIA_REQUEST_STATE_COMPLETE ||
>> + req->state == MEDIA_REQUEST_STATE_CLEANING)
>> + goto unlock;
>> +
>> + if (WARN_ON(req->state == MEDIA_REQUEST_STATE_QUEUEING))
>> + goto unlock;
>> +
>> + if (WARN_ON(!req->num_incomplete_objects))
>> + goto unlock;
>> +
>> + req->num_incomplete_objects--;
>> + if (req->state == MEDIA_REQUEST_STATE_QUEUED &&
>> + !req->num_incomplete_objects) {
>> + req->state = MEDIA_REQUEST_STATE_COMPLETE;
>> + completed = true;
>> + wake_up_interruptible(&req->poll_wait);
>> + }
>> +unlock:
>> + spin_unlock_irqrestore(&req->lock, flags);
>> + if (obj->ops->unbind)
>> + obj->ops->unbind(obj);
>> + if (completed)
>> + media_request_put(req);
>> +}
>> +EXPORT_SYMBOL_GPL(media_request_object_unbind);
>> +
>> +void media_request_object_complete(struct media_request_object *obj)
>> +{
>> + struct media_request *req = obj->req;
>> + unsigned long flags;
>> + bool completed = false;
>> +
>> + spin_lock_irqsave(&req->lock, flags);
>> + if (obj->completed)
>> + goto unlock;
>> + obj->completed = true;
>> + if (WARN_ON(!req->num_incomplete_objects) ||
>> + WARN_ON(req->state != MEDIA_REQUEST_STATE_QUEUED))
>
> If an object completes very soon after a request is queued, it is possible
> that the request is still in QUEUEING state. I'm actually beginning to
> wonder whether this state is useful; would it bring trouble if we just put
> it to QUEUED right from the beginning?
I think it would be better to split the req_queue op in two ops, so
media_request_ioctl_queue() would do this (pseudo code):
req->state = MEDIA_REQUEST_STATE_PREPARING;
ret = req->ops->req_prepare(req);
if (ret) {
req->state = IDLE;
return ret;
}
req->state = QUEUED;
req->ops->req_queue(req); // void function, must always succeed
return 0;
I think this works safely.
>
>> + goto unlock;
>> +
>> + if (!--req->num_incomplete_objects) {
>> + req->state = MEDIA_REQUEST_STATE_COMPLETE;
>> + wake_up_interruptible(&req->poll_wait);
>> + completed = true;
>> + }
>
> Newline here...
>
>> +unlock:
>> + spin_unlock_irqrestore(&req->lock, flags);
>
> and here?
>
>> + if (completed)
>> + media_request_put(req);
>> }
>> +EXPORT_SYMBOL_GPL(media_request_object_complete);
>> diff --git a/include/media/media-request.h b/include/media/media-request.h
>> index dae3eccd9aa7..baed99eb1279 100644
>> --- a/include/media/media-request.h
>> +++ b/include/media/media-request.h
>> @@ -16,7 +16,155 @@
>>
>> #include <media/media-device.h>
>>
>> +enum media_request_state {
>> + MEDIA_REQUEST_STATE_IDLE,
>> + MEDIA_REQUEST_STATE_QUEUEING,
>> + MEDIA_REQUEST_STATE_QUEUED,
>> + MEDIA_REQUEST_STATE_COMPLETE,
>> + MEDIA_REQUEST_STATE_CLEANING,
>> +};
>> +
>> +struct media_request_object;
>> +
>> +/**
>> + * struct media_request - Media device request
>
> And here (plus " *").
>
>> + * @mdev: Media device this request belongs to
>> + * @kref: Reference count
>> + * @debug_prefix: Prefix for debug messages (process name:fd)
>> + * @state: The state of the request
>> + * @objects: List of @struct media_request_object request objects
>> + * @num_objects: The number objects in the request
>> + * @num_completed_objects: The number of completed objects in the request
>> + * @poll_wait: Wait queue for poll
>> + * @lock: Serializes access to this struct
>> + */
>> +struct media_request {
>> + struct media_device *mdev;
>> + struct kref kref;
>> + char debug_str[TASK_COMM_LEN + 11];
>> + enum media_request_state state;
>> + struct list_head objects;
>> + unsigned int num_incomplete_objects;
>> + struct wait_queue_head poll_wait;
>> + spinlock_t lock;
>> +};
>> +
>> +#ifdef CONFIG_MEDIA_CONTROLLER
>> +static inline void media_request_get(struct media_request *req)
>> +{
>> + kref_get(&req->kref);
>> +}
>> +
>> +void media_request_put(struct media_request *req);
>> +
>> int media_request_alloc(struct media_device *mdev,
>> struct media_request_alloc *alloc);
>> +#else
>> +static inline void media_request_get(struct media_request *req)
>> +{
>> +}
>> +
>> +static inline void media_request_put(struct media_request *req)
>> +{
>> +}
>> +#endif
>> +
>> +struct media_request_object_ops {
>> + int (*prepare)(struct media_request_object *object);
>> + void (*unprepare)(struct media_request_object *object);
>> + void (*queue)(struct media_request_object *object);
>> + void (*unbind)(struct media_request_object *object);
>> + void (*release)(struct media_request_object *object);
>> +};
>> +
>> +/**
>> + * struct media_request_object - An opaque object that belongs to a media
>> + * request
>> + *
>> + * @priv: object's priv pointer
>> + * @list: List entry of the object for @struct media_request
>> + * @kref: Reference count of the object, acquire before releasing req->lock
>> + *
>> + * An object related to the request. This struct is embedded in the
>> + * larger object data.
>> + */
>> +struct media_request_object {
>> + const struct media_request_object_ops *ops;
>> + void *priv;
>> + struct media_request *req;
>> + struct list_head list;
>> + struct kref kref;
>> + bool completed;
>> +};
>> +
>> +#ifdef CONFIG_MEDIA_CONTROLLER
>> +static inline void media_request_object_get(struct media_request_object *obj)
>> +{
>> + kref_get(&obj->kref);
>> +}
>> +
>> +/**
>> + * media_request_object_put - Put a media request object
>> + *
>> + * @obj: The object
>> + *
>> + * Put a media request object. Once all references are gone, the
>> + * object's memory is released.
>> + */
>> +void media_request_object_put(struct media_request_object *obj);
>> +
>> +/**
>> + * media_request_object_init - Initialise a media request object
>> + *
>> + * Initialise a media request object. The object will be released using the
>> + * release callback of the ops once it has no references (this function
>> + * initialises references to one).
>> + */
>> +void media_request_object_init(struct media_request_object *obj);
>> +
>> +/**
>> + * media_request_object_bind - Bind a media request object to a request
>> + */
>> +void media_request_object_bind(struct media_request *req,
>> + const struct media_request_object_ops *ops,
>> + void *priv,
>> + struct media_request_object *obj);
>> +
>> +void media_request_object_unbind(struct media_request_object *obj);
>> +
>> +/**
>> + * media_request_object_complete - Mark the media request object as complete
>> + */
>> +void media_request_object_complete(struct media_request_object *obj);
>> +#else
>> +static inline void media_request_object_get(struct media_request_object *obj)
>> +{
>> +}
>> +
>> +static inline void media_request_object_put(struct media_request_object *obj)
>> +{
>> +}
>> +
>> +static inline void media_request_object_init(struct media_request_object *obj)
>> +{
>> + obj->ops = NULL;
>> + obj->req = NULL;
>> +}
>> +
>> +static inline void media_request_object_bind(struct media_request *req,
>> + const struct media_request_object_ops *ops,
>> + void *priv,
>> + struct media_request_object *obj)
>> +{
>> +}
>> +
>> +static inline void media_request_object_unbind(struct media_request_object *obj)
>> +{
>> +}
>> +
>> +static inline void media_request_object_complete(struct media_request_object *obj)
>> +{
>> +}
>> +#endif
>>
>> #endif
>
Regards,
Hans
