extcon: realtek: add the error handler for nvmem_cell_read

There are following smatch warning:
drivers/extcon/extcon-rtk-type-c.c:905 __updated_type_c_parameter_by_efuse()
error: 'buf' dereferencing possible ERR_PTR()

The nvmem_cell_read may fail to read. So, driver must handle failure cases.

Link: https://lore.kernel.org/all/20231016053510.28881-1-stanley_chang@realtek.com/

Fixes: 8a590d7 ("extcon: add Realtek DHC RTD SoC Type-C driver")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/a469dd51-f5d5-4e8f-ba36-6c7cea046fb8@moroto.mountain/
Signed-off-by: Stanley Chang <stanley_chang@realtek.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

drivers/extcon/extcon-rtk-type-c.c

@@ -901,25 +901,26 @@ static int __updated_type_c_parameter_by_efuse(struct type_c_data *type_c)
 		int value_mask = (BIT(value_size) - 1);
 
 		buf = nvmem_cell_read(cell, &buf_size);
-
-		cc1_0p2v = get_value((buf[0] >> value_size * 0) & value_mask);
-		cc1_0p8v = get_value((buf[0] >> value_size * 1) & value_mask);
-		cc1_2p6v = get_value((buf[1] >> value_size * 0) & value_mask);
-		cc1_0p66v = get_value((buf[1] >> value_size * 1) & value_mask);
-		cc1_1p23v = get_value((buf[2] >> value_size * 0) & value_mask);
-
-		cc2_0p2v = get_value((buf[3] >> value_size * 0) & value_mask);
-		cc2_0p8v = get_value((buf[3] >> value_size * 1) & value_mask);
-		cc2_2p6v = get_value((buf[4] >> value_size * 0) & value_mask);
-		cc2_0p66v = get_value((buf[4] >> value_size * 1) & value_mask);
-		cc2_1p23v = get_value((buf[5] >> value_size * 0) & value_mask);
-
-		cc1_4p7k = get_value((buf[6] >> value_size * 0) & value_mask);
-		cc1_12k = get_value((buf[6] >> value_size * 1) & value_mask);
-		cc2_4p7k = get_value((buf[7] >> value_size * 0) & value_mask);
-		cc2_12k = get_value((buf[7] >> value_size * 1) & value_mask);
-
-		kfree(buf);
+		if (!IS_ERR(buf)) {
+			cc1_0p2v = get_value((buf[0] >> value_size * 0) & value_mask);
+			cc1_0p8v = get_value((buf[0] >> value_size * 1) & value_mask);
+			cc1_2p6v = get_value((buf[1] >> value_size * 0) & value_mask);
+			cc1_0p66v = get_value((buf[1] >> value_size * 1) & value_mask);
+			cc1_1p23v = get_value((buf[2] >> value_size * 0) & value_mask);
+
+			cc2_0p2v = get_value((buf[3] >> value_size * 0) & value_mask);
+			cc2_0p8v = get_value((buf[3] >> value_size * 1) & value_mask);
+			cc2_2p6v = get_value((buf[4] >> value_size * 0) & value_mask);
+			cc2_0p66v = get_value((buf[4] >> value_size * 1) & value_mask);
+			cc2_1p23v = get_value((buf[5] >> value_size * 0) & value_mask);
+
+			cc1_4p7k = get_value((buf[6] >> value_size * 0) & value_mask);
+			cc1_12k = get_value((buf[6] >> value_size * 1) & value_mask);
+			cc2_4p7k = get_value((buf[7] >> value_size * 0) & value_mask);
+			cc2_12k = get_value((buf[7] >> value_size * 1) & value_mask);
+
+			kfree(buf);
+		}
 		nvmem_cell_put(cell);
 	}
 
@@ -984,29 +985,30 @@ static int __updated_type_c_parameter_by_efuse_v2(struct type_c_data *type_c)
 		int value_mask = (BIT(value_size) - 1);
 
 		buf = nvmem_cell_read(cell, &buf_size);
-
-		value_size = 5;
-		value_mask = (BIT(value_size) - 1);
-		cc1_4p7k = buf[0] & value_mask;
-		cc1_12k = buf[1] & value_mask;
-		cc2_4p7k = buf[2] & value_mask;
-		cc2_12k = buf[3] & value_mask;
-
-		value_size = 4;
-		value_mask = (BIT(value_size) - 1);
-		cc1_0p2v = (buf[4] >> value_size * 0) & value_mask;
-		cc1_0p66v = (buf[4] >> value_size * 1) & value_mask;
-		cc1_0p8v = (buf[5] >> value_size * 0) & value_mask;
-		cc1_1p23v = (buf[5] >> value_size * 1) & value_mask;
-		cc1_2p6v = (buf[6] >> value_size * 0) & value_mask;
-
-		cc2_0p2v = (buf[6] >> value_size * 1) & value_mask;
-		cc2_0p66v = (buf[7] >> value_size * 0) & value_mask;
-		cc2_0p8v = (buf[7] >> value_size * 1) & value_mask;
-		cc2_1p23v = (buf[8] >> value_size * 0) & value_mask;
-		cc2_2p6v = (buf[8] >> value_size * 1) & value_mask;
-
-		kfree(buf);
+		if (!IS_ERR(buf)) {
+			value_size = 5;
+			value_mask = (BIT(value_size) - 1);
+			cc1_4p7k = buf[0] & value_mask;
+			cc1_12k = buf[1] & value_mask;
+			cc2_4p7k = buf[2] & value_mask;
+			cc2_12k = buf[3] & value_mask;
+
+			value_size = 4;
+			value_mask = (BIT(value_size) - 1);
+			cc1_0p2v = (buf[4] >> value_size * 0) & value_mask;
+			cc1_0p66v = (buf[4] >> value_size * 1) & value_mask;
+			cc1_0p8v = (buf[5] >> value_size * 0) & value_mask;
+			cc1_1p23v = (buf[5] >> value_size * 1) & value_mask;
+			cc1_2p6v = (buf[6] >> value_size * 0) & value_mask;
+
+			cc2_0p2v = (buf[6] >> value_size * 1) & value_mask;
+			cc2_0p66v = (buf[7] >> value_size * 0) & value_mask;
+			cc2_0p8v = (buf[7] >> value_size * 1) & value_mask;
+			cc2_1p23v = (buf[8] >> value_size * 0) & value_mask;
+			cc2_2p6v = (buf[8] >> value_size * 1) & value_mask;
+
+			kfree(buf);
+		}
 		nvmem_cell_put(cell);
 	}