From: David Garbett <David.Garbett@arm.com>
Date: Mon, 2 Jul 2012 09:18:27 +0000 (+0100)
Subject: Add implementation of poll() to dma_buf using KDS
X-Git-Url: http://git.cascardo.eti.br/?a=commitdiff_plain;h=5d1bb28fa72400006b3956ab7d869dffd091af23;p=cascardo%2Flinux.git

Add implementation of poll() to dma_buf using KDS

BUG=chrome-os-partner:11949
TEST=local build, run on ARM

Change-Id: I955e12be4d52e771eccc267befff8b42f316c150
Signed-off-by: Ray Smith <Raymond.Smith@arm.com>
Reviewed-on: https://gerrit.chromium.org/gerrit/27056
Commit-Ready: John Sheu <sheu@chromium.org>
Reviewed-by: John Sheu <sheu@chromium.org>
Tested-by: John Sheu <sheu@chromium.org>
---

diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
index c286212e7d36..09e687885b0d 100644
--- a/drivers/base/dma-buf.c
+++ b/drivers/base/dma-buf.c
@@ -27,6 +27,8 @@
 #include <linux/dma-buf.h>
 #include <linux/anon_inodes.h>
 #include <linux/export.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
 
 static inline int is_dma_buf_file(struct file *);
 
@@ -40,6 +42,7 @@ static int dma_buf_release(struct inode *inode, struct file *file)
 	dmabuf = file->private_data;
 
 	dmabuf->ops->release(dmabuf);
+	kds_callback_term(&dmabuf->kds_cb);
 	kds_resource_term(&dmabuf->kds);
 	kfree(dmabuf);
 	return 0;
@@ -62,9 +65,92 @@ static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma)
 	return dmabuf->ops->mmap(dmabuf, vma);
 }
 
+
+static void dma_buf_kds_cb_fn(void *param1, void *param2)
+{
+	struct kds_resource_set **rset_ptr = param1;
+	struct kds_resource_set *rset = *rset_ptr;
+	wait_queue_head_t *wait_queue = param2;
+
+	kfree(rset_ptr);
+	kds_resource_set_release(&rset);
+	wake_up(wait_queue);
+}
+
+static int dma_buf_kds_check(struct kds_resource *kds,
+		unsigned long exclusive, int *poll_ret)
+{
+	/* Synchronous wait with 0 timeout - poll availability */
+	struct kds_resource_set *rset = kds_waitall(1, &exclusive, &kds, 0);
+
+	if (IS_ERR(rset))
+		return POLLERR;
+
+	if (rset) {
+		kds_resource_set_release(&rset);
+		*poll_ret = POLLIN | POLLRDNORM;
+		if (exclusive)
+			*poll_ret |=  POLLOUT | POLLWRNORM;
+		return 1;
+	} else {
+		return 0;
+	}
+}
+
+static unsigned int dma_buf_poll(struct file *file,
+		struct poll_table_struct *wait)
+{
+	struct dma_buf *dmabuf;
+	struct kds_resource *kds;
+	unsigned int ret = 0;
+
+	if (!is_dma_buf_file(file))
+		return POLLERR;
+
+	dmabuf = file->private_data;
+	kds    = &dmabuf->kds;
+
+	if (poll_does_not_wait(wait)) {
+		/* Check for exclusive access (superset of shared) first */
+		if (!dma_buf_kds_check(kds, 1ul, &ret))
+			dma_buf_kds_check(kds, 0ul, &ret);
+	} else {
+		int events = poll_requested_events(wait);
+		unsigned long exclusive;
+		wait_queue_head_t *wq;
+		struct kds_resource_set **rset_ptr =
+				kmalloc(sizeof(*rset_ptr), GFP_KERNEL);
+
+		if (!rset_ptr)
+			return POLL_ERR;
+
+		if (events & POLLOUT) {
+			wq = &dmabuf->wq_exclusive;
+			exclusive = 1;
+		} else {
+			wq = &dmabuf->wq_shared;
+			exclusive = 0;
+		}
+		poll_wait(file, wq, wait);
+		ret = kds_async_waitall(rset_ptr, KDS_FLAG_LOCKED_WAIT,
+				&dmabuf->kds_cb, rset_ptr, wq, 1, &exclusive,
+				&kds);
+
+		if (IS_ERR_VALUE(ret)) {
+			ret = POLL_ERR;
+			kfree(rset_ptr);
+		} else {
+			/* Can't allow access until callback */
+			ret = 0;
+		}
+	}
+	return ret;
+}
+
 static const struct file_operations dma_buf_fops = {
 	.release	= dma_buf_release,
 	.mmap		= dma_buf_mmap_internal,
+	.poll		= dma_buf_poll,
 };
 
 /*
@@ -121,7 +207,10 @@ struct dma_buf *dma_buf_export(void *priv, const struct dma_buf_ops *ops,
 	mutex_init(&dmabuf->lock);
 	INIT_LIST_HEAD(&dmabuf->attachments);
 
+	init_waitqueue_head(&dmabuf->wq_exclusive);
+	init_waitqueue_head(&dmabuf->wq_shared);
 	kds_resource_init(&dmabuf->kds);
+	kds_callback_init(&dmabuf->kds_cb, 1, dma_buf_kds_cb_fn);
 
 	return dmabuf;
 }
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 0dc41378f59c..6e824d23fa7d 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -31,6 +31,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/fs.h>
 #include <linux/kds.h>
+#include <linux/wait.h>
 
 struct device;
 struct dma_buf;
@@ -123,6 +124,9 @@ struct dma_buf {
 	/* mutex to serialize list manipulation and attach/detach */
 	struct mutex lock;
 	struct kds_resource kds;
+	wait_queue_head_t wq_exclusive;
+	wait_queue_head_t wq_shared;
+	struct kds_callback kds_cb;
 	void *priv;
 };