On 9/8/23 21:45, Jonathan Cameron wrote:
+static int bm1390_read_temp(struct bm1390_data *data, int *temp) +{ + u8 temp_reg[2] __aligned(2); + __be16 *temp_raw; + int ret; + s16 val; + bool negative; + + ret = regmap_bulk_read(data->regmap, BM1390_REG_TEMP_HI, &temp_reg, + sizeof(temp_reg)); + if (ret) + return ret; + + if (temp_reg[0] & 0x80) + negative = true; + else + negative = false; + + temp_raw = (__be16 *)&temp_reg[0]; + val = be16_to_cpu(*temp_raw); + + if (negative) { + /* + * Two's complement. I am not sure if all supported + * architectures actually use 2's complement represantation ofAFAIK they do. Many IIO drivers would be broken if not..
Great. Then I think it means we really can treat the combined value of the registers as s16 BE. Should make this much simpler :)
+ * signed ints. If yes, then we could just do the endianes + * conversion and say this is the s16 value. However, as I + * don't know, and as the conversion is pretty simple. let's + * just convert the signed 2's complement to absolute value and + * multiply by -1. + */ + val = ~val + 1; + val *= -1; + } + + *temp = val; + + return 0; +}
-- Matti Vaittinen Linux kernel developer at ROHM Semiconductors Oulu Finland ~~ When things go utterly wrong vim users can always type :help! ~~
