Darrick J. Wong wrote:
I just realized I failed to respond to this point, here is my response:
>> Why use read_byte twice in read16, but write_word in write16?
>
> A "16 bit" register is really two 8 bit register reads/writes, and the
> register with the lower address has to be read/written first. Hence the
> weird helper functions.
>
Here is the code you use for this:
+static inline int adt7470_read_word_data(struct i2c_client *client, u8 reg)
+{
+ u16 foo;
+ foo = i2c_smbus_read_byte_data(client, reg);
+ foo |= ((u16)i2c_smbus_read_byte_data(client, reg + 1) << 8);
+ return foo;
+}
+
+static inline int adt7470_write_word_data(struct i2c_client *client, u8 reg,
+ u16 value)
+{
+ u16 x = cpu_to_le16(value);
+
+ return i2c_smbus_write_word_data(client, reg, x & 0xFF)
+ && i2c_smbus_write_word_data(client, reg + 1, x >> 8);
+}
+
I understand that you need to somehow read / write a byte 2 times to get a
word, but why in adt7470_read_word_data() call i2c_smbus_read_byte_data twice?
while in adt7470_write_word_data() you use cpu_to_le16() and then
i2c_smbus_write_word_data(). Why not use i2c_smbus_read_word_data() in
adt7470_read_word_data() instead of calling i2c_smbus_read_byte_data twice?
BTW I have serious doubts about you calling cpu_to_le16(), I would expect that
i2c_smbus_write_word_data() wants the data to be in cpu endianness.
Regards,
Hans
