| Message ID | 5906381114b14d5b0359510a1d23accbd239eaa5.1538441919.git.vilhelm.gray@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | Introduce the for_each_set_clump macro | expand |
On 2018-10-02 03:14, William Breathitt Gray wrote: > /* clear bits array to a clean slate */ > bitmap_zero(bits, chip->ngpio); > > - /* get bits are evaluated a gpio port register at a time */ > - for (i = 0; i < ARRAY_SIZE(ports); i++) { > - /* gpio offset in bits array */ > - bits_offset = i * gpio_reg_size; > - > - /* word index for bits array */ > - word_index = BIT_WORD(bits_offset); > - > - /* gpio offset within current word of bits array */ > - word_offset = bits_offset % BITS_PER_LONG; > - > - /* mask of get bits for current gpio within current word */ > - word_mask = mask[word_index] & (port_mask << word_offset); > - if (!word_mask) { > - /* no get bits in this port so skip to next one */ > - continue; > - } > - > - /* read bits from current gpio port */ > + for_each_set_clump(i, word, offset, mask, ARRAY_SIZE(ports), 8) { > port_state = inb(dio48egpio->base + ports[i]); > - > - /* store acquired bits at respective bits array offset */ > - bits[word_index] |= port_state << word_offset; > + bits[word] |= port_state << offset; Somewhat unrelated to this series, but is the existing code correct? I'd expect the RHS to be masked by word_mask; otherwise we might set bits in bits[] that were not requested? And if one does that, the !word_mask test is merely an optimization to avoid reading the gpios when the result would be ignored anyway. Perhaps no caller cares. Rasmus
On Tue, Oct 02, 2018 at 09:00:45AM +0200, Rasmus Villemoes wrote: > On 2018-10-02 03:14, William Breathitt Gray wrote: > > /* clear bits array to a clean slate */ > > bitmap_zero(bits, chip->ngpio); > > > > - /* get bits are evaluated a gpio port register at a time */ > > - for (i = 0; i < ARRAY_SIZE(ports); i++) { > > - /* gpio offset in bits array */ > > - bits_offset = i * gpio_reg_size; > > - > > - /* word index for bits array */ > > - word_index = BIT_WORD(bits_offset); > > - > > - /* gpio offset within current word of bits array */ > > - word_offset = bits_offset % BITS_PER_LONG; > > - > > - /* mask of get bits for current gpio within current word */ > > - word_mask = mask[word_index] & (port_mask << word_offset); > > - if (!word_mask) { > > - /* no get bits in this port so skip to next one */ > > - continue; > > - } > > - > > - /* read bits from current gpio port */ > > + for_each_set_clump(i, word, offset, mask, ARRAY_SIZE(ports), 8) { > > port_state = inb(dio48egpio->base + ports[i]); > > - > > - /* store acquired bits at respective bits array offset */ > > - bits[word_index] |= port_state << word_offset; > > + bits[word] |= port_state << offset; > > Somewhat unrelated to this series, but is the existing code correct? I'd > expect the RHS to be masked by word_mask; otherwise we might set bits in > bits[] that were not requested? And if one does that, the !word_mask > test is merely an optimization to avoid reading the gpios when the > result would be ignored anyway. Perhaps no caller cares. > > Rasmus I don't think the caller cares in this case. Take a look at the gpiod_get_array_value_complex function: the desired inputs are collected before gpio_chip_get_multiple is called and then looped through after -- unrequested bits are simply ignored. This caller behavior also makes sense because a bit value of 0 in the bits array does not necessarily mean the input was not requested, but may instead mean that the value at the input is 0; therefore, the caller must keep track of the requested inputs rather than try to deduce them from the values in the bits array. William Breathitt Gray
On 2018-10-14 06:19, William Breathitt Gray wrote: > a bit value of 0 in the > bits array does not necessarily mean the input was not requested, but > may instead mean that the value at the input is 0; sure enough, but... > therefore, the caller > must keep track of the requested inputs rather than try to deduce them > from the values in the bits array. ...I don't agree that this logically follows. A caller might reasonably expect not to find any bits set in positions other than those in mask. A simple example would be caller that just tried to ask "are any of _these_ inputs set"; it would be reasonable to implement that using bitmap_empty() on the returned bitset, without first having to mask by the mask he passed in. Rasmus
On Mon, Oct 15, 2018 at 01:59:33PM +0200, Rasmus Villemoes wrote: > On 2018-10-14 06:19, William Breathitt Gray wrote: > > > a bit value of 0 in the > > bits array does not necessarily mean the input was not requested, but > > may instead mean that the value at the input is 0; > > sure enough, but... > > > therefore, the caller > > must keep track of the requested inputs rather than try to deduce them > > from the values in the bits array. > > ...I don't agree that this logically follows. A caller might reasonably > expect not to find any bits set in positions other than those in mask. A > simple example would be caller that just tried to ask "are any of > _these_ inputs set"; it would be reasonable to implement that using > bitmap_empty() on the returned bitset, without first having to mask by > the mask he passed in. > > Rasmus I see your point. It would be good to keep the behavior consistent with what would be expected by the user -- and adding an additional AND operation at the end to mask away the unrequested bits should not really affect the performance to a discernible degree -- so I'll submit a patchset implementing the mask for these drivers some time this weekend. William Breathitt Gray
diff --git a/drivers/gpio/gpio-104-dio-48e.c b/drivers/gpio/gpio-104-dio-48e.c index 9c4e07fcb74b..77eeaa36094c 100644 --- a/drivers/gpio/gpio-104-dio-48e.c +++ b/drivers/gpio/gpio-104-dio-48e.c @@ -183,46 +183,23 @@ static int dio48e_gpio_get(struct gpio_chip *chip, unsigned offset) return !!(port_state & mask); } +static const size_t ports[] = { 0, 1, 2, 4, 5, 6 }; + static int dio48e_gpio_get_multiple(struct gpio_chip *chip, unsigned long *mask, unsigned long *bits) { struct dio48e_gpio *const dio48egpio = gpiochip_get_data(chip); size_t i; - static const size_t ports[] = { 0, 1, 2, 4, 5, 6 }; - const unsigned int gpio_reg_size = 8; - unsigned int bits_offset; - size_t word_index; - unsigned int word_offset; - unsigned long word_mask; - const unsigned long port_mask = GENMASK(gpio_reg_size - 1, 0); + size_t word; + unsigned int offset; unsigned long port_state; /* clear bits array to a clean slate */ bitmap_zero(bits, chip->ngpio); - /* get bits are evaluated a gpio port register at a time */ - for (i = 0; i < ARRAY_SIZE(ports); i++) { - /* gpio offset in bits array */ - bits_offset = i * gpio_reg_size; - - /* word index for bits array */ - word_index = BIT_WORD(bits_offset); - - /* gpio offset within current word of bits array */ - word_offset = bits_offset % BITS_PER_LONG; - - /* mask of get bits for current gpio within current word */ - word_mask = mask[word_index] & (port_mask << word_offset); - if (!word_mask) { - /* no get bits in this port so skip to next one */ - continue; - } - - /* read bits from current gpio port */ + for_each_set_clump(i, word, offset, mask, ARRAY_SIZE(ports), 8) { port_state = inb(dio48egpio->base + ports[i]); - - /* store acquired bits at respective bits array offset */ - bits[word_index] |= port_state << word_offset; + bits[word] |= port_state << offset; } return 0; @@ -252,37 +229,25 @@ static void dio48e_gpio_set_multiple(struct gpio_chip *chip, unsigned long *mask, unsigned long *bits) { struct dio48e_gpio *const dio48egpio = gpiochip_get_data(chip); - unsigned int i; - const unsigned int gpio_reg_size = 8; - unsigned int port; - unsigned int out_port; + size_t i; + size_t word; + unsigned int offset; + unsigned int iomask; unsigned int bitmask; unsigned long flags; - /* set bits are evaluated a gpio register size at a time */ - for (i = 0; i < chip->ngpio; i += gpio_reg_size) { - /* no more set bits in this mask word; skip to the next word */ - if (!mask[BIT_WORD(i)]) { - i = (BIT_WORD(i) + 1) * BITS_PER_LONG - gpio_reg_size; - continue; - } - - port = i / gpio_reg_size; - out_port = (port > 2) ? port + 1 : port; - bitmask = mask[BIT_WORD(i)] & bits[BIT_WORD(i)]; + for_each_set_clump(i, word, offset, mask, ARRAY_SIZE(ports), 8) { + iomask = mask[word] >> offset; + bitmask = iomask & (bits[word] >> offset); raw_spin_lock_irqsave(&dio48egpio->lock, flags); /* update output state data and set device gpio register */ - dio48egpio->out_state[port] &= ~mask[BIT_WORD(i)]; - dio48egpio->out_state[port] |= bitmask; - outb(dio48egpio->out_state[port], dio48egpio->base + out_port); + dio48egpio->out_state[i] &= ~iomask; + dio48egpio->out_state[i] |= bitmask; + outb(dio48egpio->out_state[i], dio48egpio->base + ports[i]); raw_spin_unlock_irqrestore(&dio48egpio->lock, flags); - - /* prepare for next gpio register set */ - mask[BIT_WORD(i)] >>= gpio_reg_size; - bits[BIT_WORD(i)] >>= gpio_reg_size; } }
Replace verbose implementation in get_multiple/set_multiple callbacks with for_each_set_clump macro to simplify code and improve clarity. Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com> --- drivers/gpio/gpio-104-dio-48e.c | 67 ++++++++------------------------- 1 file changed, 16 insertions(+), 51 deletions(-)