[PATCH 0/5] Add GPIO set_multiple callback support for ISA_BUS_API drivers

[PATCH 0/5] Add GPIO set_multiple callback support for ISA_BUS_API drivers

[William Breathitt Gray]

Most of the ISA_BUS_API drivers control GPIO via 8-bit ioport registers.
Since updating any given GPIO line involves writing out all 8 bits for
the respective register, it makes sense to add support for the GPIO
set_multiple callback function so that multiple GPIO lines may be set
more efficiently. This patchset adds such support in each respective
driver.

William Breathitt Gray (5):
  gpio: 104-dio-48e: Add set_multiple callback function support
  gpio: 104-idio-16: Add set_multiple callback function support
  gpio: gpio-mm: Add set_multiple callback function support
  gpio: ws16c48: Add set_multiple callback function support
  iio: stx104: Add GPIO set_multiple callback function support

 drivers/gpio/gpio-104-dio-48e.c | 39 +++++++++++++++++++++++++++++++++++++++
 drivers/gpio/gpio-104-idio-16.c | 20 ++++++++++++++++++++
 drivers/gpio/gpio-gpio-mm.c     | 39 +++++++++++++++++++++++++++++++++++++++
 drivers/gpio/gpio-ws16c48.c     | 41 +++++++++++++++++++++++++++++++++++++++++
 drivers/iio/adc/stx104.c        | 23 +++++++++++++++++++++++
 5 files changed, 162 insertions(+)

-- 
2.11.0

[PATCH 1/5] gpio: 104-dio-48e: Add set_multiple callback function support

[William Breathitt Gray]

The ACCES 104-DIO-48E series provides registers where 8 lines of GPIO
may be set at a time. This patch add support for the set_multiple
callback function, thus allowing multiple GPIO output lines to be set
more efficiently in groups.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 drivers/gpio/gpio-104-dio-48e.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/gpio/gpio-104-dio-48e.c b/drivers/gpio/gpio-104-dio-48e.c
index fcf776971ca9..7bc891f1d11a 100644
--- a/drivers/gpio/gpio-104-dio-48e.c
+++ b/drivers/gpio/gpio-104-dio-48e.c
@@ -204,6 +204,44 @@ static void dio48e_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
 	spin_unlock_irqrestore(&dio48egpio->lock, flags);
 }
 
+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;
+	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)];
+
+		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);
+
+		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;
+	}
+}
+
 static void dio48e_irq_ack(struct irq_data *data)
 {
 }
@@ -328,6 +366,7 @@ static int dio48e_probe(struct device *dev, unsigned int id)
 	dio48egpio->chip.direction_output = dio48e_gpio_direction_output;
 	dio48egpio->chip.get = dio48e_gpio_get;
 	dio48egpio->chip.set = dio48e_gpio_set;
+	dio48egpio->chip.set_multiple = dio48e_gpio_set_multiple;
 	dio48egpio->base = base[id];
 	dio48egpio->irq = irq[id];
 
-- 
2.11.0

Re: [PATCH 1/5] gpio: 104-dio-48e: Add set_multiple callback function support

[Linus Walleij]

On Thu, Jan 19, 2017 at 4:05 PM, William Breathitt Gray
<vilhelm.gray@gmail.com> wrote:

> The ACCES 104-DIO-48E series provides registers where 8 lines of GPIO
> may be set at a time. This patch add support for the set_multiple
> callback function, thus allowing multiple GPIO output lines to be set
> more efficiently in groups.
>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>

Patch applied.

Yours,
Linus Walleij

[PATCH 2/5] gpio: 104-idio-16: Add set_multiple callback function support

[William Breathitt Gray]

The ACCES 104-IDIO-16 series provides registers where 8 lines of GPIO
may be set at a time. This patch add support for the set_multiple
callback function, thus allowing multiple GPIO output lines to be set
more efficiently in groups.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 drivers/gpio/gpio-104-idio-16.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/gpio/gpio-104-idio-16.c b/drivers/gpio/gpio-104-idio-16.c
index 6787b8fcf0d8..a57900fd0dc7 100644
--- a/drivers/gpio/gpio-104-idio-16.c
+++ b/drivers/gpio/gpio-104-idio-16.c
@@ -116,6 +116,25 @@ static void idio_16_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
 	spin_unlock_irqrestore(&idio16gpio->lock, flags);
 }
 
+static void idio_16_gpio_set_multiple(struct gpio_chip *chip,
+	unsigned long *mask, unsigned long *bits)
+{
+	struct idio_16_gpio *const idio16gpio = gpiochip_get_data(chip);
+	unsigned long flags;
+
+	spin_lock_irqsave(&idio16gpio->lock, flags);
+
+	idio16gpio->out_state &= ~*mask;
+	idio16gpio->out_state |= *mask & *bits;
+
+	if (*mask & 0xFF)
+		outb(idio16gpio->out_state, idio16gpio->base);
+	if ((*mask >> 8) & 0xFF)
+		outb(idio16gpio->out_state >> 8, idio16gpio->base + 4);
+
+	spin_unlock_irqrestore(&idio16gpio->lock, flags);
+}
+
 static void idio_16_irq_ack(struct irq_data *data)
 {
 }
@@ -219,6 +238,7 @@ static int idio_16_probe(struct device *dev, unsigned int id)
 	idio16gpio->chip.direction_output = idio_16_gpio_direction_output;
 	idio16gpio->chip.get = idio_16_gpio_get;
 	idio16gpio->chip.set = idio_16_gpio_set;
+	idio16gpio->chip.set_multiple = idio_16_gpio_set_multiple;
 	idio16gpio->base = base[id];
 	idio16gpio->irq = irq[id];
 	idio16gpio->out_state = 0xFFFF;
-- 
2.11.0

Re: [PATCH 2/5] gpio: 104-idio-16: Add set_multiple callback function support

[Linus Walleij]

On Thu, Jan 19, 2017 at 4:05 PM, William Breathitt Gray
<vilhelm.gray@gmail.com> wrote:

> The ACCES 104-IDIO-16 series provides registers where 8 lines of GPIO
> may be set at a time. This patch add support for the set_multiple
> callback function, thus allowing multiple GPIO output lines to be set
> more efficiently in groups.
>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>

Patch applied.

Yours,
Linus Walleij

[PATCH 3/5] gpio: gpio-mm: Add set_multiple callback function support

[William Breathitt Gray]

The Diamond Systems GPIO-MM series provides registers where 8 lines of
GPIO may be set at a time. This patch add support for the set_multiple
callback function, thus allowing multiple GPIO output lines to be set
more efficiently in groups.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 drivers/gpio/gpio-gpio-mm.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/gpio/gpio-gpio-mm.c b/drivers/gpio/gpio-gpio-mm.c
index 1e7def9449ce..093489556c54 100644
--- a/drivers/gpio/gpio-gpio-mm.c
+++ b/drivers/gpio/gpio-gpio-mm.c
@@ -192,6 +192,44 @@ static void gpiomm_gpio_set(struct gpio_chip *chip, unsigned int offset,
 	spin_unlock_irqrestore(&gpiommgpio->lock, flags);
 }
 
+static void gpiomm_gpio_set_multiple(struct gpio_chip *chip,
+	unsigned long *mask, unsigned long *bits)
+{
+	struct gpiomm_gpio *const gpiommgpio = gpiochip_get_data(chip);
+	unsigned int i;
+	const unsigned int gpio_reg_size = 8;
+	unsigned int port;
+	unsigned int out_port;
+	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)];
+
+		spin_lock_irqsave(&gpiommgpio->lock, flags);
+
+		/* update output state data and set device gpio register */
+		gpiommgpio->out_state[port] &= ~mask[BIT_WORD(i)];
+		gpiommgpio->out_state[port] |= bitmask;
+		outb(gpiommgpio->out_state[port], gpiommgpio->base + out_port);
+
+		spin_unlock_irqrestore(&gpiommgpio->lock, flags);
+
+		/* prepare for next gpio register set */
+		mask[BIT_WORD(i)] >>= gpio_reg_size;
+		bits[BIT_WORD(i)] >>= gpio_reg_size;
+	}
+}
+
 static int gpiomm_probe(struct device *dev, unsigned int id)
 {
 	struct gpiomm_gpio *gpiommgpio;
@@ -218,6 +256,7 @@ static int gpiomm_probe(struct device *dev, unsigned int id)
 	gpiommgpio->chip.direction_output = gpiomm_gpio_direction_output;
 	gpiommgpio->chip.get = gpiomm_gpio_get;
 	gpiommgpio->chip.set = gpiomm_gpio_set;
+	gpiommgpio->chip.set_multiple = gpiomm_gpio_set_multiple;
 	gpiommgpio->base = base[id];
 
 	spin_lock_init(&gpiommgpio->lock);
-- 
2.11.0

Re: [PATCH 3/5] gpio: gpio-mm: Add set_multiple callback function support

[Linus Walleij]

On Thu, Jan 19, 2017 at 4:05 PM, William Breathitt Gray
<vilhelm.gray@gmail.com> wrote:

> The Diamond Systems GPIO-MM series provides registers where 8 lines of
> GPIO may be set at a time. This patch add support for the set_multiple
> callback function, thus allowing multiple GPIO output lines to be set
> more efficiently in groups.
>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>

Patch applied.

Yours,
Linus Walleij

[PATCH 4/5] gpio: ws16c48: Add set_multiple callback function support

[William Breathitt Gray]

The WinSystems WS16C48 provides registers where 8 lines of GPIO may be
set at a time. This patch add support for the set_multiple callback
function, thus allowing multiple GPIO output lines to be set more
efficiently in groups.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 drivers/gpio/gpio-ws16c48.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/drivers/gpio/gpio-ws16c48.c b/drivers/gpio/gpio-ws16c48.c
index eaa71d440ccf..25e539530c08 100644
--- a/drivers/gpio/gpio-ws16c48.c
+++ b/drivers/gpio/gpio-ws16c48.c
@@ -155,6 +155,46 @@ static void ws16c48_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
 	spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
 }
 
+static void ws16c48_gpio_set_multiple(struct gpio_chip *chip,
+	unsigned long *mask, unsigned long *bits)
+{
+	struct ws16c48_gpio *const ws16c48gpio = gpiochip_get_data(chip);
+	unsigned int i;
+	const unsigned int gpio_reg_size = 8;
+	unsigned int port;
+	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;
+
+		/* mask out GPIO configured for input */
+		iomask = mask[BIT_WORD(i)] & ~ws16c48gpio->io_state[port];
+		bitmask = iomask & bits[BIT_WORD(i)];
+
+		spin_lock_irqsave(&ws16c48gpio->lock, flags);
+
+		/* update output state data and set device gpio register */
+		ws16c48gpio->out_state[port] &= ~iomask;
+		ws16c48gpio->out_state[port] |= bitmask;
+		outb(ws16c48gpio->out_state[port], ws16c48gpio->base + port);
+
+		spin_unlock_irqrestore(&ws16c48gpio->lock, flags);
+
+		/* prepare for next gpio register set */
+		mask[BIT_WORD(i)] >>= gpio_reg_size;
+		bits[BIT_WORD(i)] >>= gpio_reg_size;
+	}
+}
+
 static void ws16c48_irq_ack(struct irq_data *data)
 {
 	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
@@ -329,6 +369,7 @@ static int ws16c48_probe(struct device *dev, unsigned int id)
 	ws16c48gpio->chip.direction_output = ws16c48_gpio_direction_output;
 	ws16c48gpio->chip.get = ws16c48_gpio_get;
 	ws16c48gpio->chip.set = ws16c48_gpio_set;
+	ws16c48gpio->chip.set_multiple = ws16c48_gpio_set_multiple;
 	ws16c48gpio->base = base[id];
 	ws16c48gpio->irq = irq[id];
 
-- 
2.11.0

Re: [PATCH 4/5] gpio: ws16c48: Add set_multiple callback function support

[Linus Walleij]

On Thu, Jan 19, 2017 at 4:05 PM, William Breathitt Gray
<vilhelm.gray-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> The WinSystems WS16C48 provides registers where 8 lines of GPIO may be
> set at a time. This patch add support for the set_multiple callback
> function, thus allowing multiple GPIO output lines to be set more
> efficiently in groups.
>
> Signed-off-by: William Breathitt Gray <vilhelm.gray-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>

Patch applied.

Yours,
Linus Walleij

[PATCH 5/5] iio: stx104: Add GPIO set_multiple callback function support

[William Breathitt Gray]

The Apex Embedded Systems STX104 series provides a digital output
register where 4 lines may be set at a time. This patch add support for
the set_multiple callback function, thus allowing multiple digital
output lines to be set more efficiently in groups.

Cc: Jonathan Cameron <jic23-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Hartmut Knaack <knaack.h-Mmb7MZpHnFY@public.gmane.org>
Cc: Lars-Peter Clausen <lars-Qo5EllUWu/uELgA04lAiVw@public.gmane.org>
Cc: Peter Meerwald-Stadler <pmeerw-jW+XmwGofnusTnJN9+BGXg@public.gmane.org>
Signed-off-by: William Breathitt Gray <vilhelm.gray-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 drivers/iio/adc/stx104.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/iio/adc/stx104.c b/drivers/iio/adc/stx104.c
index 7e3645749eaf..6971293909f7 100644
--- a/drivers/iio/adc/stx104.c
+++ b/drivers/iio/adc/stx104.c
@@ -266,6 +266,28 @@ static void stx104_gpio_set(struct gpio_chip *chip, unsigned int offset,
 	spin_unlock_irqrestore(&stx104gpio->lock, flags);
 }
 
+static void stx104_gpio_set_multiple(struct gpio_chip *chip,
+	unsigned long *mask, unsigned long *bits)
+{
+	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
+	unsigned long flags;
+
+	/* verify masked GPIO are output */
+	if (!(*mask & 0xF0))
+		return;
+
+	*mask >>= 4;
+	*bits >>= 4;
+
+	spin_lock_irqsave(&stx104gpio->lock, flags);
+
+	stx104gpio->out_state &= ~*mask;
+	stx104gpio->out_state |= *mask & *bits;
+	outb(stx104gpio->out_state, stx104gpio->base);
+
+	spin_unlock_irqrestore(&stx104gpio->lock, flags);
+}
+
 static int stx104_probe(struct device *dev, unsigned int id)
 {
 	struct iio_dev *indio_dev;
@@ -330,6 +352,7 @@ static int stx104_probe(struct device *dev, unsigned int id)
 	stx104gpio->chip.direction_output = stx104_gpio_direction_output;
 	stx104gpio->chip.get = stx104_gpio_get;
 	stx104gpio->chip.set = stx104_gpio_set;
+	stx104gpio->chip.set_multiple = stx104_gpio_set_multiple;
 	stx104gpio->base = base[id] + 3;
 	stx104gpio->out_state = 0x0;
 
-- 
2.11.0

Re: [PATCH 5/5] iio: stx104: Add GPIO set_multiple callback function support

[Jonathan Cameron]

On 19/01/17 15:06, William Breathitt Gray wrote:
> The Apex Embedded Systems STX104 series provides a digital output
> register where 4 lines may be set at a time. This patch add support for
> the set_multiple callback function, thus allowing multiple digital
> output lines to be set more efficiently in groups.
> 
> Cc: Jonathan Cameron <jic23@kernel.org>
> Cc: Hartmut Knaack <knaack.h@gmx.de>
> Cc: Lars-Peter Clausen <lars@metafoo.de>
> Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Acked-by: Jonathan Cameron <jic23@kernel.org>
> ---
>  drivers/iio/adc/stx104.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/drivers/iio/adc/stx104.c b/drivers/iio/adc/stx104.c
> index 7e3645749eaf..6971293909f7 100644
> --- a/drivers/iio/adc/stx104.c
> +++ b/drivers/iio/adc/stx104.c
> @@ -266,6 +266,28 @@ static void stx104_gpio_set(struct gpio_chip *chip, unsigned int offset,
>  	spin_unlock_irqrestore(&stx104gpio->lock, flags);
>  }
>  
> +static void stx104_gpio_set_multiple(struct gpio_chip *chip,
> +	unsigned long *mask, unsigned long *bits)
> +{
> +	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
> +	unsigned long flags;
> +
> +	/* verify masked GPIO are output */
> +	if (!(*mask & 0xF0))
> +		return;
> +
> +	*mask >>= 4;
> +	*bits >>= 4;
> +
> +	spin_lock_irqsave(&stx104gpio->lock, flags);
> +
> +	stx104gpio->out_state &= ~*mask;
> +	stx104gpio->out_state |= *mask & *bits;
> +	outb(stx104gpio->out_state, stx104gpio->base);
> +
> +	spin_unlock_irqrestore(&stx104gpio->lock, flags);
> +}
> +
>  static int stx104_probe(struct device *dev, unsigned int id)
>  {
>  	struct iio_dev *indio_dev;
> @@ -330,6 +352,7 @@ static int stx104_probe(struct device *dev, unsigned int id)
>  	stx104gpio->chip.direction_output = stx104_gpio_direction_output;
>  	stx104gpio->chip.get = stx104_gpio_get;
>  	stx104gpio->chip.set = stx104_gpio_set;
> +	stx104gpio->chip.set_multiple = stx104_gpio_set_multiple;
>  	stx104gpio->base = base[id] + 3;
>  	stx104gpio->out_state = 0x0;
>  
> 

Re: [PATCH 5/5] iio: stx104: Add GPIO set_multiple callback function support

[William Breathitt Gray]

On Sun, Jan 22, 2017 at 01:23:07PM +0000, Jonathan Cameron wrote:
>On 19/01/17 15:06, William Breathitt Gray wrote:
>> The Apex Embedded Systems STX104 series provides a digital output
>> register where 4 lines may be set at a time. This patch add support for
>> the set_multiple callback function, thus allowing multiple digital
>> output lines to be set more efficiently in groups.
>> 
>> Cc: Jonathan Cameron <jic23@kernel.org>
>> Cc: Hartmut Knaack <knaack.h@gmx.de>
>> Cc: Lars-Peter Clausen <lars@metafoo.de>
>> Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
>> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
>Acked-by: Jonathan Cameron <jic23@kernel.org>

Jonathan Cameron,

Would you pick this patch up in one of your iio.git branches?

Thanks,

William Breathitt Gray

Re: [PATCH 5/5] iio: stx104: Add GPIO set_multiple callback function support

[Jonathan Cameron]

On 31/01/17 20:03, William Breathitt Gray wrote:
> On Sun, Jan 22, 2017 at 01:23:07PM +0000, Jonathan Cameron wrote:
>> On 19/01/17 15:06, William Breathitt Gray wrote:
>>> The Apex Embedded Systems STX104 series provides a digital output
>>> register where 4 lines may be set at a time. This patch add support for
>>> the set_multiple callback function, thus allowing multiple digital
>>> output lines to be set more efficiently in groups.
>>>
>>> Cc: Jonathan Cameron <jic23@kernel.org>
>>> Cc: Hartmut Knaack <knaack.h@gmx.de>
>>> Cc: Lars-Peter Clausen <lars@metafoo.de>
>>> Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
>>> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
>> Acked-by: Jonathan Cameron <jic23@kernel.org>
> 
> Jonathan Cameron,
> 
> Would you pick this patch up in one of your iio.git branches?
Sure.  For some reason I got into my head this should go via the gpio
tree, but no reason why really.

Anyhow, applied, but there was some fuzz.

Applied to the toreg branch of iio.git and pushed out as testing for
the autobuilders to play with it.

Thanks.

Jonathan
> 
> Thanks,
> 
> William Breathitt Gray
> 

Re: [PATCH 5/5] iio: stx104: Add GPIO set_multiple callback function support

[Linus Walleij]

On Thu, Jan 19, 2017 at 4:06 PM, William Breathitt Gray
<vilhelm.gray@gmail.com> wrote:

> The Apex Embedded Systems STX104 series provides a digital output
> register where 4 lines may be set at a time. This patch add support for
> the set_multiple callback function, thus allowing multiple digital
> output lines to be set more efficiently in groups.
>
> Cc: Jonathan Cameron <jic23@kernel.org>
> Cc: Hartmut Knaack <knaack.h@gmx.de>
> Cc: Lars-Peter Clausen <lars@metafoo.de>
> Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Best if Jonathan queues this so the changes reside in the
IIO tree.

Yours,
Linus Walleij