[3/8] gpio: pci-idio-16: Implement get_multiple callback

Message ID e6a13288c45f824ba23ee8d1410cf0bf9c55fe60.1520886945.git.vilhelm.gray@gmail.com
State New
Headers show
Series
  • Implement get_multiple for ACCES and PC104 drivers
Related show

Commit Message

William Breathitt Gray March 12, 2018, 8:49 p.m.
The ACCES I/O PCI-IDIO-16 series of devices provides 16
optically-isolated digital inputs accessed via two 8-bit ports. Since
eight input lines are acquired on a single port input read, the
PCI-IDIO-16 GPIO driver may improve multiple input reads by utilizing a
get_multiple callback. This patch implements the
idio_16_gpio_get_multiple function which serves as the respective
get_multiple callback.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 drivers/gpio/gpio-pci-idio-16.c | 48 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

Comments

kbuild test robot March 13, 2018, 2:32 p.m. | #1
Hi William,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.16-rc5 next-20180313]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/William-Breathitt-Gray/Implement-get_multiple-for-ACCES-and-PC104-drivers/20180313-202244
config: x86_64-randconfig-x015-201810 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   drivers//gpio/gpio-pci-idio-16.c: In function 'idio_16_gpio_get_multiple':
>> drivers//gpio/gpio-pci-idio-16.c:147:35: warning: 'port_state' may be used uninitialized in this function [-Wmaybe-uninitialized]
      bits[BIT_WORD(i)] |= port_state << bit_word_offset;
                           ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~

vim +/port_state +147 drivers//gpio/gpio-pci-idio-16.c

   105	
   106	static int idio_16_gpio_get_multiple(struct gpio_chip *chip,
   107		unsigned long *mask, unsigned long *bits)
   108	{
   109		struct idio_16_gpio *const idio16gpio = gpiochip_get_data(chip);
   110		unsigned int i;
   111		const unsigned int gpio_reg_size = 8;
   112		unsigned int bit_word_offset;
   113		unsigned int bits_mask;
   114		const unsigned long reg_mask = GENMASK(gpio_reg_size, 0);
   115		unsigned long port_state;
   116	
   117		/* clear bits array to a clean slate */
   118		for (i = 0; i < chip->ngpio; i += BITS_PER_LONG)
   119			bits[i / BITS_PER_LONG] = 0;
   120	
   121		/* get bits are evaluated a gpio register size at a time */
   122		for (i = 0; i < chip->ngpio; i += gpio_reg_size) {
   123			bit_word_offset = i % BITS_PER_LONG;
   124			bits_mask = mask[BIT_WORD(i)] & (reg_mask << bit_word_offset);
   125			if (!bits_mask) {
   126				/* no get bits in this register so skip to next one */
   127				continue;
   128			}
   129	
   130			/* read bits from current gpio register */
   131			switch (i / gpio_reg_size) {
   132			case 0:
   133				port_state = ioread8(&idio16gpio->reg->out0_7);
   134				break;
   135			case 1:
   136				port_state = ioread8(&idio16gpio->reg->out8_15);
   137				break;
   138			case 2:
   139				port_state = ioread8(&idio16gpio->reg->in0_7);
   140				break;
   141			case 3:
   142				port_state = ioread8(&idio16gpio->reg->in8_15);
   143				break;
   144			}
   145	
   146			/* store acquired bits */
 > 147			bits[BIT_WORD(i)] |= port_state << bit_word_offset;
   148		}
   149	
   150		return 0;
   151	}
   152	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
Andy Shevchenko March 13, 2018, 4:04 p.m. | #2
On Mon, Mar 12, 2018 at 10:49 PM, William Breathitt Gray
<vilhelm.gray@gmail.com> wrote:

> +static int idio_16_gpio_get_multiple(struct gpio_chip *chip,
> +       unsigned long *mask, unsigned long *bits)
> +{


> +       /* clear bits array to a clean slate */
> +       for (i = 0; i < chip->ngpio; i += BITS_PER_LONG)
> +               bits[i / BITS_PER_LONG] = 0;

bitmap_clear() or bitmap_zero()

> +       /* get bits are evaluated a gpio register size at a time */
> +       for (i = 0; i < chip->ngpio; i += gpio_reg_size) {
> +               bit_word_offset = i % BITS_PER_LONG;
> +               bits_mask = mask[BIT_WORD(i)] & (reg_mask << bit_word_offset);
> +               if (!bits_mask) {
> +                       /* no get bits in this register so skip to next one */
> +                       continue;
> +               }

for_each_set_bit() ?

> +               /* store acquired bits */
> +               bits[BIT_WORD(i)] |= port_state << bit_word_offset;

__set_bit()
__clear_bit()

We have bitmap API for *ages*. Is it too hard to check?
William Breathitt Gray March 13, 2018, 8:20 p.m. | #3
On Tue, Mar 13, 2018 at 06:04:33PM +0200, Andy Shevchenko wrote:
>On Mon, Mar 12, 2018 at 10:49 PM, William Breathitt Gray
><vilhelm.gray@gmail.com> wrote:
>
>> +static int idio_16_gpio_get_multiple(struct gpio_chip *chip,
>> +       unsigned long *mask, unsigned long *bits)
>> +{
>
>
>> +       /* clear bits array to a clean slate */
>> +       for (i = 0; i < chip->ngpio; i += BITS_PER_LONG)
>> +               bits[i / BITS_PER_LONG] = 0;
>
>bitmap_clear() or bitmap_zero()

bitmap_zero() would be perfect for this situation. I'll submit a version
2 of this patchset with this change for the various drivers herein.

>
>> +       /* get bits are evaluated a gpio register size at a time */
>> +       for (i = 0; i < chip->ngpio; i += gpio_reg_size) {
>> +               bit_word_offset = i % BITS_PER_LONG;
>> +               bits_mask = mask[BIT_WORD(i)] & (reg_mask << bit_word_offset);
>> +               if (!bits_mask) {
>> +                       /* no get bits in this register so skip to next one */
>> +                       continue;
>> +               }
>
>for_each_set_bit() ?
>
>> +               /* store acquired bits */
>> +               bits[BIT_WORD(i)] |= port_state << bit_word_offset;
>
>__set_bit()
>__clear_bit()

I'm not sure for_each_set_bit() and __set_bit()/__clear_bit() would be
good for this particular situation since I'm working with the entire
register word (8 bits for this specific device) at a time.

Since I know each register word is 8-bits, I can make 8-bit jumps and
skips rather than evaluating each bit individually. Similarly, it seems
more efficient to store the input 8 bits at a time rather than breaking
it up to individual bits.

However, I do see how all these inline bitwise operations could make it
difficult to follow the code, so perhaps I can break it up across more
lines so that the logic of the loop becomes easier to read.

William Breathitt Gray

>
>We have bitmap API for *ages*. Is it too hard to check?
>
>-- 
>With Best Regards,
>Andy Shevchenko
--
To unsubscribe from this list: send the line "unsubscribe linux-gpio" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

diff --git a/drivers/gpio/gpio-pci-idio-16.c b/drivers/gpio/gpio-pci-idio-16.c
index 57d1b7fbf07b..8c5ec301c7ff 100644
--- a/drivers/gpio/gpio-pci-idio-16.c
+++ b/drivers/gpio/gpio-pci-idio-16.c
@@ -103,6 +103,53 @@  static int idio_16_gpio_get(struct gpio_chip *chip, unsigned int offset)
 	return !!(ioread8(&idio16gpio->reg->in8_15) & (mask >> 24));
 }
 
+static int idio_16_gpio_get_multiple(struct gpio_chip *chip,
+	unsigned long *mask, unsigned long *bits)
+{
+	struct idio_16_gpio *const idio16gpio = gpiochip_get_data(chip);
+	unsigned int i;
+	const unsigned int gpio_reg_size = 8;
+	unsigned int bit_word_offset;
+	unsigned int bits_mask;
+	const unsigned long reg_mask = GENMASK(gpio_reg_size, 0);
+	unsigned long port_state;
+
+	/* clear bits array to a clean slate */
+	for (i = 0; i < chip->ngpio; i += BITS_PER_LONG)
+		bits[i / BITS_PER_LONG] = 0;
+
+	/* get bits are evaluated a gpio register size at a time */
+	for (i = 0; i < chip->ngpio; i += gpio_reg_size) {
+		bit_word_offset = i % BITS_PER_LONG;
+		bits_mask = mask[BIT_WORD(i)] & (reg_mask << bit_word_offset);
+		if (!bits_mask) {
+			/* no get bits in this register so skip to next one */
+			continue;
+		}
+
+		/* read bits from current gpio register */
+		switch (i / gpio_reg_size) {
+		case 0:
+			port_state = ioread8(&idio16gpio->reg->out0_7);
+			break;
+		case 1:
+			port_state = ioread8(&idio16gpio->reg->out8_15);
+			break;
+		case 2:
+			port_state = ioread8(&idio16gpio->reg->in0_7);
+			break;
+		case 3:
+			port_state = ioread8(&idio16gpio->reg->in8_15);
+			break;
+		}
+
+		/* store acquired bits */
+		bits[BIT_WORD(i)] |= port_state << bit_word_offset;
+	}
+
+	return 0;
+}
+
 static void idio_16_gpio_set(struct gpio_chip *chip, unsigned int offset,
 	int value)
 {
@@ -299,6 +346,7 @@  static int idio_16_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	idio16gpio->chip.direction_input = idio_16_gpio_direction_input;
 	idio16gpio->chip.direction_output = idio_16_gpio_direction_output;
 	idio16gpio->chip.get = idio_16_gpio_get;
+	idio16gpio->chip.get_multiple = idio_16_gpio_get_multiple;
 	idio16gpio->chip.set = idio_16_gpio_set;
 	idio16gpio->chip.set_multiple = idio_16_gpio_set_multiple;