[PATCH v4 02/17] clk: Check that ops of composite clock components exist before calling

[Sean Anderson <seanga2@gmail.com>]

clk_composite_ops was shared between all devices in the composite clock
driver.  If one clock had a feature (such as supporting set_parent) which
another clock did not, it could call a null pointer dereference.

This patch does three things
1. It adds null-pointer checks to all composite clock functions.
2. It makes clk_composite_ops const and sets its functions at compile-time.
3. It adds some basic sanity checks to num_parents.

The combined effect of these changes is that any of mux, rate, or gate can
be NULL, and composite clocks will still function normally. Previously, at
least mux had to exist, since clk_composite_get_parent was used to
determine the parent for clk_register.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Acked-by: Lukasz Majewski <lukma@denx.de>
---

Changes in v4:
- Return ENOTSUPP not ENOSYS with no set_parent

Changes in v3:
- Don't return an error code where a no-op would be fine

 drivers/clk/clk-composite.c | 57 +++++++++++++++++++++++--------------
 1 file changed, 35 insertions(+), 22 deletions(-)

diff --git a/drivers/clk/clk-composite.c b/drivers/clk/clk-composite.c
index 3d84036c9e..bcf6b9c689 100644
--- a/drivers/clk/clk-composite.c
+++ b/drivers/clk/clk-composite.c
@@ -22,7 +22,10 @@ static u8 clk_composite_get_parent(struct clk *clk)
 		(struct clk *)dev_get_clk_ptr(clk->dev) : clk);
 	struct clk *mux = composite->mux;
 
-	return clk_mux_get_parent(mux);
+	if (mux)
+		return clk_mux_get_parent(mux);
+	else
+		return 0;
 }
 
 static int clk_composite_set_parent(struct clk *clk, struct clk *parent)
@@ -32,7 +35,10 @@ static int clk_composite_set_parent(struct clk *clk, struct clk *parent)
 	const struct clk_ops *mux_ops = composite->mux_ops;
 	struct clk *mux = composite->mux;
 
-	return mux_ops->set_parent(mux, parent);
+	if (mux && mux_ops)
+		return mux_ops->set_parent(mux, parent);
+	else
+		return -ENOTSUPP;
 }
 
 static unsigned long clk_composite_recalc_rate(struct clk *clk)
@@ -42,7 +48,10 @@ static unsigned long clk_composite_recalc_rate(struct clk *clk)
 	const struct clk_ops *rate_ops = composite->rate_ops;
 	struct clk *rate = composite->rate;
 
-	return rate_ops->get_rate(rate);
+	if (rate && rate_ops)
+		return rate_ops->get_rate(rate);
+	else
+		return clk_get_parent_rate(clk);
 }
 
 static ulong clk_composite_set_rate(struct clk *clk, unsigned long rate)
@@ -52,7 +61,10 @@ static ulong clk_composite_set_rate(struct clk *clk, unsigned long rate)
 	const struct clk_ops *rate_ops = composite->rate_ops;
 	struct clk *clk_rate = composite->rate;
 
-	return rate_ops->set_rate(clk_rate, rate);
+	if (rate && rate_ops)
+		return rate_ops->set_rate(clk_rate, rate);
+	else
+		return clk_get_rate(clk);
 }
 
 static int clk_composite_enable(struct clk *clk)
@@ -62,7 +74,10 @@ static int clk_composite_enable(struct clk *clk)
 	const struct clk_ops *gate_ops = composite->gate_ops;
 	struct clk *gate = composite->gate;
 
-	return gate_ops->enable(gate);
+	if (gate && gate_ops)
+		return gate_ops->enable(gate);
+	else
+		return 0;
 }
 
 static int clk_composite_disable(struct clk *clk)
@@ -72,15 +87,12 @@ static int clk_composite_disable(struct clk *clk)
 	const struct clk_ops *gate_ops = composite->gate_ops;
 	struct clk *gate = composite->gate;
 
-	gate_ops->disable(gate);
-
-	return 0;
+	if (gate && gate_ops)
+		return gate_ops->disable(gate);
+	else
+		return 0;
 }
 
-struct clk_ops clk_composite_ops = {
-	/* This will be set according to clk_register_composite */
-};
-
 struct clk *clk_register_composite(struct device *dev, const char *name,
 				   const char * const *parent_names,
 				   int num_parents, struct clk *mux,
@@ -94,7 +106,9 @@ struct clk *clk_register_composite(struct device *dev, const char *name,
 	struct clk *clk;
 	struct clk_composite *composite;
 	int ret;
-	struct clk_ops *composite_ops = &clk_composite_ops;
+
+	if (!num_parents || (num_parents != 1 && !mux))
+		return ERR_PTR(-EINVAL);
 
 	composite = kzalloc(sizeof(*composite), GFP_KERNEL);
 	if (!composite)
@@ -103,8 +117,6 @@ struct clk *clk_register_composite(struct device *dev, const char *name,
 	if (mux && mux_ops) {
 		composite->mux = mux;
 		composite->mux_ops = mux_ops;
-		if (mux_ops->set_parent)
-			composite_ops->set_parent = clk_composite_set_parent;
 		mux->data = (ulong)composite;
 	}
 
@@ -113,11 +125,6 @@ struct clk *clk_register_composite(struct device *dev, const char *name,
 			clk = ERR_PTR(-EINVAL);
 			goto err;
 		}
-		composite_ops->get_rate = clk_composite_recalc_rate;
-
-		/* .set_rate requires either .round_rate or .determine_rate */
-		if (rate_ops->set_rate)
-			composite_ops->set_rate = clk_composite_set_rate;
 
 		composite->rate = rate;
 		composite->rate_ops = rate_ops;
@@ -132,8 +139,6 @@ struct clk *clk_register_composite(struct device *dev, const char *name,
 
 		composite->gate = gate;
 		composite->gate_ops = gate_ops;
-		composite_ops->enable = clk_composite_enable;
-		composite_ops->disable = clk_composite_disable;
 		gate->data = (ulong)composite;
 	}
 
@@ -159,6 +164,14 @@ err:
 	return clk;
 }
 
+static const struct clk_ops clk_composite_ops = {
+	.set_parent = clk_composite_set_parent,
+	.get_rate = clk_composite_recalc_rate,
+	.set_rate = clk_composite_set_rate,
+	.enable = clk_composite_enable,
+	.disable = clk_composite_disable,
+};
+
 U_BOOT_DRIVER(clk_composite) = {
 	.name	= UBOOT_DM_CLK_COMPOSITE,
 	.id	= UCLASS_CLK,
-- 
2.25.0