Re: [PATCH v13 01/11] bitops: Introduce the for_each_set_clump8 macro
On Thu, Mar 28, 2019 at 01:30:13PM +0900, William Breathitt Gray wrote: > On Wed, Mar 27, 2019 at 07:42:54AM +0100, Lukas Wunner wrote: > > On Wed, Mar 27, 2019 at 01:58:45PM +0900, William Breathitt Gray 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. > > > > I would have preferred static inlines for bitmap_get_value8(), > > bitmap_set_value8() and find_next_clump8() to make this as fast > > as possible in the callers because I've personally worked with > > an industrial application where the GPIO pins of a 74x164 are > > written every 250 usec. > > I'm not sure these can be static inline since the symbols are exported > for use outside this file. By static inlines I meant that the functions are moved to the appropriate header file in include/linux/. You don't need to worry about exporting in that case as the code is local to each module. For smallish functions like these, static inlines are usually fine. See drivers/dma/virt-dma.h for an extreme case of static inlines (as compared to the much smaller virt-dma.c). Thanks, Lukas
Re: [PATCH v13 01/11] bitops: Introduce the for_each_set_clump8 macro
On Wed, Mar 27, 2019 at 07:42:54AM +0100, Lukas Wunner wrote: > On Wed, Mar 27, 2019 at 01:58:45PM +0900, William Breathitt Gray 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. > > I would have preferred static inlines for bitmap_get_value8(), > bitmap_set_value8() and find_next_clump8() to make this as fast > as possible in the callers because I've personally worked with > an industrial application where the GPIO pins of a 74x164 are > written every 250 usec. > > But apart from that I like this series a lot, thanks for working on it. > > Lukas I'm not sure these can be static inline since the symbols are exported for use outside this file. However, in theory I have no objection from a performance standpoint. Since my devices don't have such strict realtime requirements as your 74x164 application, I'll defer this decision to someone more knowledgeable in this area; perhaps someone else can comment in this thread with their advice and suggestions. William Breathitt Gray
Re: [PATCH v13 01/11] bitops: Introduce the for_each_set_clump8 macro
On Wed, Mar 27, 2019 at 01:58:45PM +0900, William Breathitt Gray 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.
> +unsigned long bitmap_get_value8(const unsigned long *addr, unsigned long
> start)
> +{
> + const size_t idx = BIT_WORD(start);
> + const unsigned long offset = start % BITS_PER_LONG;
> +
> + return (addr[idx] >> offset) & 0xFF;
I would spell index instead of idx, but it's minor and up to you.
> +}
--
With Best Regards,
Andy Shevchenko
Re: [PATCH v13 01/11] bitops: Introduce the for_each_set_clump8 macro
On Wed, Mar 27, 2019 at 01:58:45PM +0900, William Breathitt Gray 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. I would have preferred static inlines for bitmap_get_value8(), bitmap_set_value8() and find_next_clump8() to make this as fast as possible in the callers because I've personally worked with an industrial application where the GPIO pins of a 74x164 are written every 250 usec. But apart from that I like this series a lot, thanks for working on it. Lukas
