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MAX6642: Better detection schema

PATCH Superseded Per Dalén 2 participants 2 messages May 25, 2011 Hardware monitoring

v1 of 2 Superseded Latest is v2 →

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Per Dalén

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#0 lore raw

PATCH 1/1 MAX6642: Better detection schema

Made the improvement for the detection schema suggested by Guenter Roeck.
---
Check for non-existing registers, registers 0x04, 0x06 and 0xff, which are supported by other Maxim chips. Reading such registers returns the previously read value.

Signed-off-by Per Dalen <[email protected]>

---

drivers/hwmon/max6642.c +18 -4
index 0f9fc40..69c7f9e 100644
@@ -64,6 +64,14 @@ static const unsigned short normal_i2c[] = {
 #define MAX6642_REG_W_REMOTE_HIGH	0x0D
 
 /*
+ * Registers for detection tests, these registers isn't pressent and
+ * will only show the last valid register read.
+ */
+#define MAX6642_REG_R_DUMMY_1          0x04
+#define MAX6642_REG_R_DUMMY_2          0x06
+#define MAX6642_REG_R_DUMMY_3          0xFF
+
+/*
  * Conversions
  */
 

@@ -126,14 +134,16 @@ static int max6642_detect(struct i2c_client *client,
 			  struct i2c_board_info *info)
 {
 	struct i2c_adapter *adapter = client->adapter;
-	u8 reg_config, reg_status, man_id;
+	u8 reg_config, reg_status, man_id, dummy_reg1, dummy_reg2;
 
 	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
 		return -ENODEV;
 
 	/* identification */
 	man_id = i2c_smbus_read_byte_data(client, MAX6642_REG_R_MAN_ID);
-	if (man_id != 0x4D)
+	dummy_reg1 = i2c_smbus_read_byte_data(client, MAX6642_REG_R_DUMMY_1);
+	if ((man_id != 0x4D) &&
+	    (man_id != dummy_reg1))
 		return -ENODEV;
 
 	/*

@@ -142,9 +152,13 @@ static int max6642_detect(struct i2c_client *client,
 	 * zero in the status register.
 	 */
 	reg_config = i2c_smbus_read_byte_data(client, MAX6642_REG_R_CONFIG);
+	dummy_reg1 = i2c_smbus_read_byte_data(client, MAX6642_REG_R_DUMMY_2);
 	reg_status = i2c_smbus_read_byte_data(client, MAX6642_REG_R_STATUS);
-	if (((reg_config & 0x0f) != 0x00) ||
-	    ((reg_status & 0x2b) != 0x00))
+	dummy_reg2 = i2c_smbus_read_byte_data(client, MAX6642_REG_R_DUMMY_3);
+	if ((reg_config & 0x0f) != 0x00 ||
+	    (reg_status & 0x2b) != 0x00 ||
+	    reg_config != dummy_reg1 ||
+	    reg_status != dummy_reg2)
 		return -ENODEV;
 
 	strlcpy(info->type, "max6642", I2C_NAME_SIZE);

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#1 lore raw

Hi Per,

Quoted 34 lines · Per Dalén

Made the improvement for the detection schema suggested by Guenter Roeck.
---
Check for non-existing registers, registers 0x04, 0x06 and 0xff, which are supported by other Maxim chips. Reading such registers returns the previously read value.

Signed-off-by Per Dalen <[email protected]>

---

drivers/hwmon/max6642.c +9 -1
index 0f9fc40..69c7f9e 100644
@@ -64,6 +64,14 @@ static const unsigned short normal_i2c[] = {
 #define MAX6642_REG_W_REMOTE_HIGH	0x0D
 
 /*
+ * Registers for detection tests, these registers isn't pressent and
+ * will only show the last valid register read.
+ */
+#define MAX6642_REG_R_DUMMY_1          0x04
+#define MAX6642_REG_R_DUMMY_2          0x06
+#define MAX6642_REG_R_DUMMY_3          0xFF
+
+/*
  * Conversions
  */
 

@@ -126,14 +134,16 @@ static int max6642_detect(struct i2c_client *client,
 			  struct i2c_board_info *info)
 {
 	struct i2c_adapter *adapter = client->adapter;
-	u8 reg_config, reg_status, man_id;
+	u8 reg_config, reg_status, man_id, dummy_reg1, dummy_reg2;

drivers/hwmon/max6642.c static int max6642_detect(struct i2c_client *client, · line 146

Quoted 10 lines
drivers/hwmon/max6642.c +3 -1
 
 	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
 		return -ENODEV;
 
 	/* identification */
 	man_id = i2c_smbus_read_byte_data(client, MAX6642_REG_R_MAN_ID);
-	if (man_id != 0x4D)
+	dummy_reg1 = i2c_smbus_read_byte_data(client, MAX6642_REG_R_DUMMY_1);
+	if ((man_id != 0x4D) &&
+	    (man_id != dummy_reg1))

Please drop all the unnecessary () and the unnecessary line break. Also, I think the logic is wrong. It should be

	if (man_id != 0x4d || man_id != dummy_reg1)
Quoted 6 lines
drivers/hwmon/max6642.c +0 -0
 		return -ENODEV;
 
 	/*

@@ -142,9 +152,13 @@ static int max6642_detect(struct i2c_client *client,
 	 * zero in the status register.
 	 */

drivers/hwmon/max6642.c static int max6642_detect(struct i2c_client *client, · line 161

Quoted 10 lines
drivers/hwmon/max6642.c +6 -2
 	reg_config = i2c_smbus_read_byte_data(client, MAX6642_REG_R_CONFIG);
+	dummy_reg1 = i2c_smbus_read_byte_data(client, MAX6642_REG_R_DUMMY_2);
 	reg_status = i2c_smbus_read_byte_data(client, MAX6642_REG_R_STATUS);
-	if (((reg_config & 0x0f) != 0x00) ||
-	    ((reg_status & 0x2b) != 0x00))
+	dummy_reg2 = i2c_smbus_read_byte_data(client, MAX6642_REG_R_DUMMY_3);
+	if ((reg_config & 0x0f) != 0x00 ||
+	    (reg_status & 0x2b) != 0x00 ||
+	    reg_config != dummy_reg1 ||
+	    reg_status != dummy_reg2)

Please remove unnecessary line breaks.

I think it is better to read all dummy registers right after reading man_id. This way we know for sure that the MAX6642 will return 0x4d when reading those registers, and you can check each of the registers against man_id in the first if statement above.

Thanks,
Guenter

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