| Message ID | 20240801144918.6156-2-linux@roeck-us.net (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | hwmon: (lm92) Cleanup and conversion to with_info API | expand |
On Thu, Aug 01, 2024 at 07:49:13AM -0700, Guenter Roeck wrote: > Checking three configuration register bits and the manufacturer ID > register to auto-detect LM92 is a bit vague. Repeat twice on replicated > register addresses to improve detection accuracy. Check the manufacturer > ID first and bail out immediately without reading the other register if > there is a mismatch to reduce the number of i2c transfers needed in that > case. Also explicitly test for an error from reading the configuration > register to avoid potential situations where the returned error masked > against 0xe0 is 0. > > While at it, drop "lm92: Found National Semiconductor LM92 chip" detection > noise. > > Signed-off-by: Guenter Roeck <linux@roeck-us.net> Reviewed-by: Tzung-Bi Shih <tzungbi@kernel.org>
diff --git a/drivers/hwmon/lm92.c b/drivers/hwmon/lm92.c index 46579a3e1715..e2d8c8afcbfa 100644 --- a/drivers/hwmon/lm92.c +++ b/drivers/hwmon/lm92.c @@ -272,20 +272,28 @@ static int lm92_detect(struct i2c_client *new_client, struct i2c_board_info *info) { struct i2c_adapter *adapter = new_client->adapter; - u8 config; - u16 man_id; + u8 config_addr = LM92_REG_CONFIG; + u8 man_id_addr = LM92_REG_MAN_ID; + int i, regval; if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA)) return -ENODEV; - config = i2c_smbus_read_byte_data(new_client, LM92_REG_CONFIG); - man_id = i2c_smbus_read_word_data(new_client, LM92_REG_MAN_ID); - - if ((config & 0xe0) == 0x00 && man_id == 0x0180) - pr_info("lm92: Found National Semiconductor LM92 chip\n"); - else - return -ENODEV; + /* + * Register values repeat with multiples of 8. + * Read twice to improve detection accuracy. + */ + for (i = 0; i < 2; i++) { + regval = i2c_smbus_read_word_data(new_client, man_id_addr); + if (regval != 0x0180) + return -ENODEV; + regval = i2c_smbus_read_byte_data(new_client, config_addr); + if (regval < 0 || (regval & 0xe0)) + return -ENODEV; + config_addr += 8; + man_id_addr += 8; + } strscpy(info->type, "lm92", I2C_NAME_SIZE);
Checking three configuration register bits and the manufacturer ID register to auto-detect LM92 is a bit vague. Repeat twice on replicated register addresses to improve detection accuracy. Check the manufacturer ID first and bail out immediately without reading the other register if there is a mismatch to reduce the number of i2c transfers needed in that case. Also explicitly test for an error from reading the configuration register to avoid potential situations where the returned error masked against 0xe0 is 0. While at it, drop "lm92: Found National Semiconductor LM92 chip" detection noise. Signed-off-by: Guenter Roeck <linux@roeck-us.net> --- drivers/hwmon/lm92.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-)