Hi Andy, On Thu, Oct 10, 2019 at 7:49 AM Andy Shevchenko <andy.shevchenko@xxxxxxxxx> wrote: > On Thu, Oct 10, 2019 at 5:31 AM Masahiro Yamada > <yamada.masahiro@xxxxxxxxxxxxx> wrote: > > On Thu, Oct 10, 2019 at 3:54 AM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > > > On Wed, Oct 9, 2019 at 7:09 PM Andy Shevchenko > > > <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote: > > > > On Thu, Oct 10, 2019 at 01:28:08AM +0900, Masahiro Yamada wrote: > > > > > On Thu, Oct 10, 2019 at 12:27 AM William Breathitt Gray > > > > > <vilhelm.gray@xxxxxxxxx> wrote: > > > > > > > > > > > > This macro iterates for each 8-bit group of bits (clump) with set bits, > > > > > > within a bitmap memory region. For each iteration, "start" is set to the > > > > > > bit offset of the found clump, while the respective clump value is > > > > > > stored to the location pointed by "clump". Additionally, the > > > > > > bitmap_get_value8 and bitmap_set_value8 functions are introduced to > > > > > > respectively get and set an 8-bit value in a bitmap memory region. > > > > > > > > > Why is the return type "unsigned long" where you know > > > > > it return the 8-bit value ? > > > > > > > > Because bitmap API operates on unsigned long type. This is not only > > > > consistency, but for sake of flexibility in case we would like to introduce > > > > more calls like clump16 or so. > > > > > > TBH, that doesn't convince me: those functions explicitly take/return an > > > 8-bit value, and have "8" in their name. The 8-bit value is never > > > really related to, retrieved from, or stored in a full "unsigned long" > > > element of a bitmap, only to/from/in a part (byte) of it. > > > > > > Following your rationale, all of iowrite{8,16,32,64}*() should take an > > > "unsigned long" value, too. > > > > > > > +1 > > > > Using u8/u16/u32/u64 looks more consistent with other bitmap helpers. > > > > void bitmap_from_arr32(unsigned long *bitmap, const u32 *buf, unsigned > > int nbits); > > void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap, unsigned int nbits); > > static inline void bitmap_from_u64(unsigned long *dst, u64 mask); > > > > > > > > If you want to see more examples from other parts, > > Geert's and yours examples both are not related. They are about > fixed-width properies when we know that is the part of protocol. > Here we have no protocol which stricts us to the mentioned fixed-width types. Yes you have: they are functions to store/retrieve an 8-bit value from the middle of the bitmap, which is reflected in their names ("clump8", "value8"). The input/output value is clearly separated from the actual bitmap, which is referenced by the "unsigned long *". If you add new "value16" functions, they will be intended to store/retrieve 16-bit values. Besides, if retrieving an 8-bit value requires passing an "unsigned long *", the caller needs two variables: one unsigned long to pass the address of, and one u8 to copy the returned value into. > So, I can tell an opposite, your arguments didn't convince me. > > Imagine the function which does an or / and / xor operation on bitmap. > Now, when I supply unsigned long, I will see > operations on one type in _one_ function independently of the size. > Your proposal will make an unneded churn. Depends on what kind of value you will use to do the logical operation with the bitmap: - Full bitmap => unsigned long * + size, - Single bitmap "word" => unsigned long, - 8-bit value => u8, - 16-bit value => u16 Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx 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