Messages in this thread | | | Subject | Re: [PATCH] lm75: add lm75b detection | From | Guenter Roeck <> | Date | Sun, 27 Oct 2019 16:03:39 -0700 |
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On 10/26/19 1:10 AM, Rain Wang wrote: > The National Semiconductor LM75B is very similar as the > LM75A, but it has no ID byte register 7, and unused registers > return 0xff rather than the last read value like LM75A. > > Signed-off-by: Rain Wang <rain_wang@jabil.com>
I am quite hesitant to touch the detect function for this chip. Each addition increases the risk for false positives. What is the use case ?
Thanks, Guenter
> --- > drivers/hwmon/lm75.c | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c > index 5e6392294c03..a718f9eb4d72 100644 > --- a/drivers/hwmon/lm75.c > +++ b/drivers/hwmon/lm75.c > @@ -760,6 +760,7 @@ static int lm75_detect(struct i2c_client *new_client, > int i; > int conf, hyst, os; > bool is_lm75a = 0; > + bool is_lm75b = 0; > > if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA | > I2C_FUNC_SMBUS_WORD_DATA)) > @@ -780,8 +781,12 @@ static int lm75_detect(struct i2c_client *new_client, > * register 7, and unused registers return 0xff rather than the > * last read value. > * > + * The National Semiconductor LM75B is very similar as the > + * LM75A, but it has no ID byte register 7, and unused registers > + * return 0xff rather than the last read value like LM75A. > + * > * Note that this function only detects the original National > - * Semiconductor LM75 and the LM75A. Clones from other vendors > + * Semiconductor LM75 and the LM75A/B. Clones from other vendors > * aren't detected, on purpose, because they are typically never > * found on PC hardware. They are found on embedded designs where > * they can be instantiated explicitly so detection is not needed. > @@ -806,6 +811,13 @@ static int lm75_detect(struct i2c_client *new_client, > is_lm75a = 1; > hyst = i2c_smbus_read_byte_data(new_client, 2); > os = i2c_smbus_read_byte_data(new_client, 3); > + } else if (i2c_smbus_read_byte_data(new_client, 4) == 0xff > + && i2c_smbus_read_byte_data(new_client, 5) == 0xff > + && i2c_smbus_read_byte_data(new_client, 6) == 0xff) { > + /* LM75B detection */ > + is_lm75b = 1; > + hyst = i2c_smbus_read_byte_data(new_client, 2); > + os = i2c_smbus_read_byte_data(new_client, 3); > } else { /* Traditional style LM75 detection */ > /* Unused addresses */ > hyst = i2c_smbus_read_byte_data(new_client, 2); > @@ -839,7 +851,8 @@ static int lm75_detect(struct i2c_client *new_client, > return -ENODEV; > } > > - strlcpy(info->type, is_lm75a ? "lm75a" : "lm75", I2C_NAME_SIZE); > + strlcpy(info->type, is_lm75a ? > + "lm75a" : (is_lm75b ? "lm75b" : "lm75"), I2C_NAME_SIZE); > > return 0; > } >
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