On 06/12/16 11:42, Geert Uytterhoeven wrote: > On Tue, Dec 6, 2016 at 11:31 AM, Sebastian Frias <s...@laposte.net> wrote: >> On 05/12/16 18:48, Geert Uytterhoeven wrote: >>> On Mon, Dec 5, 2016 at 2:36 PM, Sebastian Frias <s...@laposte.net> wrote: >>>> Introduce SETBITFIELD(msb, lsb, value) macro to ease dealing with >>>> continuous bitfields, just as BIT(x) does for single bits. >>> >>> If it's a bitfield, why not calling it that way? >> >> I don't know if you saw v2 (or v3 for that matter), but the name was changed >> to GENVALUE. > > ... which means "generate a value"?? >
Yes. Although I'm not sure if I understood the essence of your point. Are you suggesting that the name should be GENERATE_A_VALUE? There's already GENMASK, which "generates a mask". >> Also a small use case was added to the commit message: >> >> "Introduce GENVALUE(msb, lsb, value) macro..." >> "...This is useful mostly for creating values to be packed together >> via OR operations, ex: >> >> u32 val = 0x11110000; >> val |= GENVALUE(19, 12, 0x5a); > > "val |= 0x5a << 12;" looks much more readable to me... > Well, the idea behind this is that one can use it like: (see https://marc.info/?l=linux-kernel&m=148095872915717&w=2) ... #define TIMEOUT_CLK_UNIT_MHZ BIT(6) #define BUS_CLK_FREQ_FOR_SD_CLK(x) GENVALUE(14,7,x) ... val = 0; val |= TIMEOUT_CLK_UNIT_MHZ; /* unit: MHz */ val |= BUS_CLK_FREQ_FOR_SD_CLK(200); /* SDIO clock: 200MHz */ ... which makes it very practical for writing macros for associated HW documentation. >> now 'val = 0x1115a000'" >> >>> So what about BITFIELD(start ,size), like arch/tile/kernel/tile-desc_32.c >>> has? >>> >>>> SETBITFIELD_ULL(msb, lsb, value) macro is also added. >>> >>> Confused by the need for a "value" parameter... >> >> "value" is the value to be massaged (shifted, masked) into a [msb:lsb] >> bitfield. > > OK. So it inserts a value into a bitfield. > > Yes, that can be useful. Now let's find a sensible name for this. > Perhaps inspired by a PowerPC mnemonic? At least that would be more > obvious than "GENVALUE", IMHO... I'm open to suggestions. > > Gr{oetje,eeting}s, > > Geert > > -- > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- > ge...@linux-m68k.org > > In personal conversations with technical people, I call myself a hacker. But > when I'm talking to journalists I just say "programmer" or something like > that. > -- Linus Torvalds >
