On Fri, Jun 10, 2022 at 7:53 AM Xiaohui Zhang <xiaohuizhang@xxxxxxxxxx> wrote: > > Similar to the handling of read/write in commit 108e4d4de2b5 > ("iio:proximity:sx9324: Fix hardware gain read/write"), we thought > a patch might be needed here as well. > > There are four possible gain values according to 'sx9360_gain_vals[]': > > 1, 2, 4, and 8 > > The values are off by one when writing and reading the register. The > bits should be set according to this equation: > > ilog2(<gain>) + 1 > > so that a gain of 8 is 0x4 in the register field and a gain of 4 is 0x3 > in the register field, etc. Note that a gain of 0 is reserved per the > datasheet. The default gain (SX9360_REG_PROX_CTRL0_GAIN_1) is also > wrong. It should be 0x1 << 3, i.e. 0x8, not 0x80 which is setting the > reserved bit 7. > > Fix this all up to properly handle the hardware gain and return errors > for invalid settings. ... > + regval = FIELD_GET(SX9360_REG_PROX_CTRL0_GAIN_MASK, regval); > + if (regval) > + regval--; > + else if (regval == SX9360_REG_PROX_CTRL0_GAIN_RSVD || > + regval > SX9360_REG_PROX_CTRL0_GAIN_8) else?! Isn't it a dead code? How has it been tested? > + return -EINVAL; > + *val = 1 << regval; Even in the original code this is wrong in accordance with C standard. It might have potentially UB. BIT(), for example, solves this issue. You may do what it does under the hood. -- With Best Regards, Andy Shevchenko