On Mon, Apr 22, 2024 at 7:10 AM Jacky Huang <ychuang570808@xxxxxxxxx> wrote: > On 2024/4/10 下午 04:54, Andy Shevchenko wrote: ... > >> +#define MA35_GP_MODE_MASK_WIDTH 2 > >> + > >> +#define MA35_GP_SLEWCTL_MASK_WIDTH 2 > > I looked at the code how you use these... Oh, please switch to FIELD_GET() / > > FIELD_PREP() (don't forget to include bitfield.h) > > > > ... > > > > ... > >> + regval &= ~GENMASK(setting->shift + MA35_MFP_BITS_PER_PORT - 1, > >> + setting->shift); > > This will generate an awful code. Use respective FIELD_*() macros. > > > > ... > > > >> + regval &= ~GENMASK(gpio * MA35_GP_MODE_MASK_WIDTH - 1, > >> + gpio * MA35_GP_MODE_MASK_WIDTH); > >> + regval |= mode << gpio * MA35_GP_MODE_MASK_WIDTH; > > Ditto. > > > > ... > > > >> + regval &= GENMASK(gpio * MA35_GP_MODE_MASK_WIDTH - 1, > >> + gpio * MA35_GP_MODE_MASK_WIDTH); > >> + > >> + return regval >> gpio * MA35_GP_MODE_MASK_WIDTH; > > Ditto. ... > Allow me to remove irrelevant parts. > > I attempted to follow your advice and use FIELD_GET() and FIELD_PREP(), > but found > it impractical. The reason is that these two macros require their 'mask' > argument > to be a constant, otherwise compilation errors occur, which is the issue > I encountered. > Since the mask here is calculated and not a constant, compilation errors > occur. > > Taking MA35_GP_REG_MODE as an example, within 32 bits, every 2 bits > represent > the mode of a GPIO pin, and the mask is obtained by GENMASK(gpio * 2 -1, > gpio * 2), This is not good for the compiler, it can't figure out (at least in some _supported_ by Linux kernel versions on some architectures) that GENMASK can be constant here just left-shifted by arbitrary bits. > where the 'gpio' argument is a variable, not a constant, leading to > compilation > errors. > > Due to this reason, I will leave this part unchanged, or do you have any > other suggestions? If you need non-constant field_get()/field_prep(), add a new patch that moves them from drivers/iio/temperature/mlx90614.c (and there are more custom implementations: https://elixir.bootlin.com/linux/latest/A/ident/field_get) to the bitfield.h and use them in your code. -- With Best Regards, Andy Shevchenko
