Hi Sebastian, On Tue, Dec 6, 2016 at 12:03 PM, Sebastian Frias <s...@laposte.net> wrote: > 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?
No. I mean that "value" is a way too generic name. Hence "GENVALUE" may be suitable for a macro local to a driver, but is way too generic and fuzzy for a global function. > There's already GENMASK, which "generates a mask". Yes. And it generates a (bit)mask, which is clear from its name. But a "value" is just too generic for a global function, and make me think of a pseudo-random number generator ;-) >>> 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. Actually I more like the SETBITFIELD name... >>> 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. BITFIELD_INSERT()? 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
