[PATCH 3/7] Functions to fetch POSIX dynamic clock object

[Erez Geva]

Add kernel functions to fetch a pointer to a POSIX dynamic clock
using a user file description dynamic clock ID.

Signed-off-by: Erez Geva <erez.geva.ext@xxxxxxxxxxx>
---
 include/linux/posix-clock.h | 39 +++++++++++++++++++
 kernel/time/posix-clock.c   | 76 +++++++++++++++++++++++++++++++++++++
 2 files changed, 115 insertions(+)

diff --git a/include/linux/posix-clock.h b/include/linux/posix-clock.h
index 468328b1e1dd..e90bd90d3a01 100644
--- a/include/linux/posix-clock.h
+++ b/include/linux/posix-clock.h
@@ -116,4 +116,43 @@ int posix_clock_register(struct posix_clock *clk, struct device *dev);
  */
 void posix_clock_unregister(struct posix_clock *clk);
 
+/**
+ * posix_clock_get_clock() - get reference to a posix clock
+ * @id: A user clockid that uses a posix clock
+ *
+ * Used by kernel code to get a reference to a posix clock.
+ * Increase the reference count, ensure the referece is not removed.
+ */
+struct posix_clock *posix_clock_get_clock(clockid_t id);
+
+/**
+ * posix_clock_put_clock() - release a reference to a posix clock
+ * @clk: The reference to a posix clock to release
+ *
+ * Release a reference to a posix clock.
+ * Reduce the reference count.
+ */
+int posix_clock_put_clock(struct posix_clock *clk);
+
+/**
+ * posix_clock_gettime() - get time from posix clock
+ * @clk: A reference to a posix clock
+ * @ts: pointer to a time structure used to store the time from the posix clock
+ *
+ * Retrieve the time from a posix clock.
+ * In case the clock device was removed, the function return error.
+ */
+int posix_clock_gettime(struct posix_clock *clk, struct timespec64 *ts);
+
+/**
+ * posix_clock_adjtime() - get tune parameters from posix clock
+ * @clk: A reference to a posix clock
+ * @tx: pointer to a kernel timex structure used to store
+ *      the tune parameters from the posix clock
+ *
+ * Retrieve the tune parameters from a posix clock.
+ * In case the clock device was removed, the function return error.
+ */
+int posix_clock_adjtime(struct posix_clock *clk, struct __kernel_timex *tx);
+
 #endif
diff --git a/kernel/time/posix-clock.c b/kernel/time/posix-clock.c
index 77c0c2370b6d..1e205eea6ebd 100644
--- a/kernel/time/posix-clock.c
+++ b/kernel/time/posix-clock.c
@@ -315,3 +315,79 @@ const struct k_clock clock_posix_dynamic = {
 	.clock_get_timespec	= pc_clock_gettime,
 	.clock_adj		= pc_clock_adjtime,
 };
+
+struct posix_clock *posix_clock_get_clock(clockid_t id)
+{
+	int err;
+	struct posix_clock_desc cd;
+
+	/* Verify we use posix clock ID */
+	if (!is_clockid_fd_clock(id))
+		return ERR_PTR(-EINVAL);
+
+	err = get_clock_desc(id, &cd);
+	if (err)
+		return ERR_PTR(err);
+
+	get_device(cd.clk->dev);
+
+	put_clock_desc(&cd);
+
+	return cd.clk;
+}
+EXPORT_SYMBOL_GPL(posix_clock_get_clock);
+
+int posix_clock_put_clock(struct posix_clock *clk)
+{
+	if (IS_ERR_OR_NULL(clk))
+		return -EINVAL;
+	put_device(clk->dev);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(posix_clock_put_clock);
+
+int posix_clock_gettime(struct posix_clock *clk, struct timespec64 *ts)
+{
+	int err;
+
+	if (IS_ERR_OR_NULL(clk))
+		return -EINVAL;
+
+	down_read(&clk->rwsem);
+
+	if (clk->zombie)
+		err = -ENODEV;
+	else if (clk->ops.clock_gettime)
+		err = clk->ops.clock_gettime(clk, ts);
+	else
+		err = -EOPNOTSUPP;
+
+	up_read(&clk->rwsem);
+	return err;
+}
+EXPORT_SYMBOL_GPL(posix_clock_gettime);
+
+int posix_clock_adjtime(struct posix_clock *clk, struct __kernel_timex *tx)
+{
+	int err;
+
+	/* Allow read only */
+	if (tx->modes != 0)
+		return -EINVAL;
+
+	if (IS_ERR_OR_NULL(clk))
+		return -EINVAL;
+
+	down_read(&clk->rwsem);
+
+	if (clk->zombie)
+		err = -ENODEV;
+	else if (clk->ops.clock_adjtime)
+		err = clk->ops.clock_adjtime(clk, tx);
+	else
+		err = -EOPNOTSUPP;
+
+	up_read(&clk->rwsem);
+	return err;
+}
+EXPORT_SYMBOL_GPL(posix_clock_adjtime);
-- 
2.20.1