[PATCH] clk: mux: let clk_mux_val_to_index return U8_MAX in the error case

[Heiner Kallweit <hkallweit1@gmail.com>]

Currently this function may return a negative errno, but almost no
user checks for the error case. Only imx_clk_gpr_mux_get_parent()
does, but mentions in a comment that they'd prefer a dummy value.
Other users cast the negative errno to u8 instead, what may result
in unwanted results.
Let's deal with this by returning u8 and U8_MAX in the error case.
Then clk_core_get_parent_by_index() can detect that the index is
out of range.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 drivers/clk/clk-mux.c        | 8 ++++----
 include/linux/clk-provider.h | 4 ++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/clk/clk-mux.c b/drivers/clk/clk-mux.c
index fa817c317..be0f317ee 100644
--- a/drivers/clk/clk-mux.c
+++ b/drivers/clk/clk-mux.c
@@ -40,8 +40,8 @@ static inline void clk_mux_writel(struct clk_mux *mux, u32 val)
 		writel(val, mux->reg);
 }
 
-int clk_mux_val_to_index(struct clk_hw *hw, const u32 *table, unsigned int flags,
-			 unsigned int val)
+u8 clk_mux_val_to_index(struct clk_hw *hw, const u32 *table, unsigned int flags,
+			unsigned int val)
 {
 	int num_parents = clk_hw_get_num_parents(hw);
 
@@ -51,7 +51,7 @@ int clk_mux_val_to_index(struct clk_hw *hw, const u32 *table, unsigned int flags
 		for (i = 0; i < num_parents; i++)
 			if (table[i] == val)
 				return i;
-		return -EINVAL;
+		return U8_MAX;
 	}
 
 	if (val && (flags & CLK_MUX_INDEX_BIT))
@@ -61,7 +61,7 @@ int clk_mux_val_to_index(struct clk_hw *hw, const u32 *table, unsigned int flags
 		val--;
 
 	if (val >= num_parents)
-		return -EINVAL;
+		return U8_MAX;
 
 	return val;
 }
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index faad3cdc1..62fb4118c 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -1069,8 +1069,8 @@ struct clk *clk_register_mux_table(struct device *dev, const char *name,
 			      NULL, (parent_data), (flags), (reg), (shift),   \
 			      BIT((width)) - 1, (clk_mux_flags), table, (lock))
 
-int clk_mux_val_to_index(struct clk_hw *hw, const u32 *table, unsigned int flags,
-			 unsigned int val);
+u8 clk_mux_val_to_index(struct clk_hw *hw, const u32 *table, unsigned int flags,
+			unsigned int val);
 unsigned int clk_mux_index_to_val(const u32 *table, unsigned int flags, u8 index);
 
 void clk_unregister_mux(struct clk *clk);
-- 
2.40.0