linux-kernel - [PATCH 1/7] RFC: media: Add media_request

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Message-Id: <20241220-media-rpi-hevc-dec-v1-1-0ebcc04ed42e@raspberrypi.com>
Date: Fri, 20 Dec 2024 16:21:12 +0000
From: Dave Stevenson <dave.stevenson@...pberrypi.com>
To: Sakari Ailus <sakari.ailus@...ux.intel.com>, 
 Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Florian Fainelli <florian.fainelli@...adcom.com>, 
 Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>, 
 John Cox <john.cox@...pberrypi.com>, Dom Cobley <dom@...pberrypi.com>, 
 review list <kernel-list@...pberrypi.com>, 
 Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
Cc: John Cox <jc@...esim.co.uk>, linux-media@...r.kernel.org, 
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-rpi-kernel@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, 
 Dave Stevenson <dave.stevenson@...pberrypi.com>, 
 John Cox <john.cox@...pberypi.com>
Subject: [PATCH 1/7] RFC: media: Add media_request_{pin,unpin} API

From: Ezequiel Garcia <ezequiel@...guardiasur.com.ar>

This is probably not the API we will want to add, but it
should show what semantics are needed by drivers.

The goal is to allow the OUTPUT (aka source) buffer and the
controls associated to a request to be released from the request,
and in particular return the OUTPUT buffer back to userspace,
without signalling the media request fd.

This is useful for devices that are able to pre-process
the OUTPUT buffer, therefore able to release it before
the decoding is finished. These drivers should signal
the media request fd only after the CAPTURE buffer is done.

Tested-by: John Cox <john.cox@...pberypi.com>
Signed-off-by: Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
Signed-off-by: Dave Stevenson <dave.stevenson@...pberrypi.com>
---
 drivers/media/mc/mc-request.c | 35 +++++++++++++++++++++++++++++++++++
 include/media/media-request.h | 12 ++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/drivers/media/mc/mc-request.c b/drivers/media/mc/mc-request.c
index 5edfc2791ce7..b5334389d846 100644
--- a/drivers/media/mc/mc-request.c
+++ b/drivers/media/mc/mc-request.c
@@ -499,3 +499,38 @@ void media_request_object_complete(struct media_request_object *obj)
 		media_request_put(req);
 }
 EXPORT_SYMBOL_GPL(media_request_object_complete);
+
+void media_request_pin(struct media_request *req)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&req->lock, flags);
+	if (WARN_ON(req->state != MEDIA_REQUEST_STATE_QUEUED))
+		goto unlock;
+	req->num_incomplete_objects++;
+unlock:
+	spin_unlock_irqrestore(&req->lock, flags);
+}
+EXPORT_SYMBOL_GPL(media_request_pin);
+
+void media_request_unpin(struct media_request *req)
+{
+	unsigned long flags;
+	bool completed = false;
+
+	spin_lock_irqsave(&req->lock, flags);
+	if (WARN_ON(!req->num_incomplete_objects) ||
+	    WARN_ON(req->state != MEDIA_REQUEST_STATE_QUEUED))
+		goto unlock;
+
+	if (!--req->num_incomplete_objects) {
+		req->state = MEDIA_REQUEST_STATE_COMPLETE;
+		wake_up_interruptible_all(&req->poll_wait);
+		completed = true;
+	}
+unlock:
+	spin_unlock_irqrestore(&req->lock, flags);
+	if (completed)
+		media_request_put(req);
+}
+EXPORT_SYMBOL_GPL(media_request_unpin);
diff --git a/include/media/media-request.h b/include/media/media-request.h
index d4ac557678a7..c48cfb710959 100644
--- a/include/media/media-request.h
+++ b/include/media/media-request.h
@@ -189,6 +189,10 @@ static inline void media_request_get(struct media_request *req)
  */
 void media_request_put(struct media_request *req);
 
+void media_request_pin(struct media_request *req);
+
+void media_request_unpin(struct media_request *req);
+
 /**
  * media_request_get_by_fd - Get a media request by fd
  *
@@ -228,6 +232,14 @@ static inline void media_request_put(struct media_request *req)
 {
 }
 
+static inline void media_request_pin(struct media_request *req)
+{
+}
+
+static inline void media_request_unpin(struct media_request *req)
+{
+}
+
 static inline struct media_request *
 media_request_get_by_fd(struct media_device *mdev, int request_fd)
 {

-- 
2.34.1