Jakub Kicinski <[email protected]> writes: > Common approach to accessing register fields is to define > structures or sets of macros containing mask and shift pair. > Operations on the register are then performed as follows: > > field = (reg >> shift) & mask; > > reg &= ~(mask << shift); > reg |= (field & mask) << shift; > > Defining shift and mask separately is tedious. Ivo van Doorn > came up with an idea of computing them at compilation time > based on a single shifted mask (later refined by Felix) which > can be used like this: > > #define REG_FIELD 0x000ff000 > > field = FIELD_GET(REG_FIELD, reg); > > reg &= ~REG_FIELD; > reg |= FIELD_PUT(REG_FIELD, field); > > FIELD_{GET,PUT} macros take care of finding out what the > appropriate shift is based on compilation time ffs operation. > > GENMASK can be used to define registers (which is usually > less error-prone and easier to match with datasheets). > > This approach is the most convenient I've seen so to limit code > multiplication let's move the macros to a global header file. > Attempts to use static inlines instead of macros failed due > to false positive triggering of BUILD_BUG_ON()s, especially with > GCC < 6.0. > > Signed-off-by: Jakub Kicinski <[email protected]> > Reviewed-by: Dinan Gunawardena <[email protected]>
Are people ok with this? I think they are useful and I can take these through my tree, but I would prefer to get an ack from other maintainers first. Dave? Andrew? Full patches here: https://patchwork.kernel.org/patch/9284153/ https://patchwork.kernel.org/patch/9284155/ -- Kalle Valo
