Re: [PATCH v5 1/4] gpiolib: Pass bitmaps, not integer arrays, to get/set array

Miguel Ojeda
2018-08-30T11:11:24Z

Hi Janusz,

On Wed, Aug 29, 2018 at 10:48 PM, Janusz Krzysztofik
<jmkrzyszt@gmail.com> wrote:
> Most users of get/set array functions iterate consecutive bits of data,
> usually a single integer, while processing array of results obtained
> from, or building an array of values to be passed to those functions.
> Save time wasted on those iterations by changing the functions' API to
> accept bitmaps.
>
> All current users are updated as well.
>
> More benefits from the change are expected as soon as planned support
> for accepting/passing those bitmaps directly from/to respective GPIO
> chip callbacks if applicable is implemented.
>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Miguel Ojeda Sandonis <miguel.ojeda.sandonis@gmail.com>
> Cc: Peter Korsgaard <peter.korsgaard@barco.com>
> Cc: Peter Rosin <peda@axentia.se>
> Cc: Andrew Lunn <andrew@lunn.ch>
> Cc: Florian Fainelli <f.fainelli@gmail.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Dominik Brodowski <linux@dominikbrodowski.net>
> Cc: Kishon Vijay Abraham I <kishon@ti.com>
> Cc: Lars-Peter Clausen <lars@metafoo.de>
> Cc: Michael Hennerich <Michael.Hennerich@analog.com>
> Cc: Jonathan Cameron <jic23@kernel.org>
> Cc: Hartmut Knaack <knaack.h@gmx.de>
> Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Jiri Slaby <jslaby@suse.com>
> Signed-off-by: Janusz Krzysztofik <jmkrzyszt@gmail.com>
> Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
> ---
> Documentation/driver-api/gpio/consumer.rst | 22 ++++----
> drivers/auxdisplay/hd44780.c | 52 +++++++++--------
> drivers/bus/ts-nbus.c | 19 ++-----
> drivers/gpio/gpio-max3191x.c | 17 +++---
> drivers/gpio/gpiolib.c | 86 +++++++++++++++--------------
> drivers/gpio/gpiolib.h | 4 +-
> drivers/i2c/muxes/i2c-mux-gpio.c | 8 +--
> drivers/mmc/core/pwrseq_simple.c | 13 ++---
> drivers/mux/gpio.c | 9 +--
> drivers/net/phy/mdio-mux-gpio.c | 3 +-
> drivers/pcmcia/soc_common.c | 11 ++--
> drivers/phy/motorola/phy-mapphone-mdm6600.c | 17 +++---
> drivers/staging/iio/adc/ad7606.c | 9 +--
> drivers/tty/serial/serial_mctrl_gpio.c | 7 ++-
> include/linux/gpio/consumer.h | 18 +++---
> 15 files changed, 140 insertions(+), 155 deletions(-)
>
> diff --git a/Documentation/driver-api/gpio/consumer.rst b/Documentation/driver-api/gpio/consumer.rst
> index aa03f389d41d..ed68042ddccf 100644
> --- a/Documentation/driver-api/gpio/consumer.rst
> +++ b/Documentation/driver-api/gpio/consumer.rst
> @@ -323,29 +323,29 @@ The following functions get or set the values of an array of GPIOs::
>
> int gpiod_get_array_value(unsigned int array_size,
> struct gpio_desc **desc_array,
> - int *value_array);
> + unsigned long *value_bitmap);
> int gpiod_get_raw_array_value(unsigned int array_size,
> struct gpio_desc **desc_array,
> - int *value_array);
> + unsigned long *value_bitmap);
> int gpiod_get_array_value_cansleep(unsigned int array_size,
> struct gpio_desc **desc_array,
> - int *value_array);
> + unsigned long *value_bitmap);
> int gpiod_get_raw_array_value_cansleep(unsigned int array_size,
> struct gpio_desc **desc_array,
> - int *value_array);
> + unsigned long *value_bitmap);
>
> void gpiod_set_array_value(unsigned int array_size,
> struct gpio_desc **desc_array,
> - int *value_array)
> + unsigned long *value_bitmap)
> void gpiod_set_raw_array_value(unsigned int array_size,
> struct gpio_desc **desc_array,
> - int *value_array)
> + unsigned long *value_bitmap)
> void gpiod_set_array_value_cansleep(unsigned int array_size,
> struct gpio_desc **desc_array,
> - int *value_array)
> + unsigned long *value_bitmap)
> void gpiod_set_raw_array_value_cansleep(unsigned int array_size,
> struct gpio_desc **desc_array,
> - int *value_array)
> + unsigned long *value_bitmap)
>
> The array can be an arbitrary set of GPIOs. The functions will try to access
> GPIOs belonging to the same bank or chip simultaneously if supported by the
> @@ -356,8 +356,8 @@ accessed sequentially.
> The functions take three arguments:
> * array_size - the number of array elements
> * desc_array - an array of GPIO descriptors
> - * value_array - an array to store the GPIOs' values (get) or
> - an array of values to assign to the GPIOs (set)
> + * value_bitmap - a bitmap to store the GPIOs' values (get) or
> + a bitmap of values to assign to the GPIOs (set)
>
> The descriptor array can be obtained using the gpiod_get_array() function
> or one of its variants. If the group of descriptors returned by that function
> @@ -366,7 +366,7 @@ the struct gpio_descs returned by gpiod_get_array()::
>
> struct gpio_descs *my_gpio_descs = gpiod_get_array(...);
> gpiod_set_array_value(my_gpio_descs->ndescs, my_gpio_descs->desc,
> - my_gpio_values);
> + my_gpio_value_bitmap);
>
> It is also possible to access a completely arbitrary array of descriptors. The
> descriptors may be obtained using any combination of gpiod_get() and
> diff --git a/drivers/auxdisplay/hd44780.c b/drivers/auxdisplay/hd44780.c
> index f1a42f0f1ded..bbbd6a29bf01 100644
> --- a/drivers/auxdisplay/hd44780.c
> +++ b/drivers/auxdisplay/hd44780.c
> @@ -62,20 +62,19 @@ static void hd44780_strobe_gpio(struct hd44780 *hd)
> /* write to an LCD panel register in 8 bit GPIO mode */
> static void hd44780_write_gpio8(struct hd44780 *hd, u8 val, unsigned int rs)
> {
> - int values[10]; /* for DATA[0-7], RS, RW */
> - unsigned int i, n;
> + unsigned long value_bitmap[1]; /* for DATA[0-7], RS, RW */

(I read your comments in the other email)

I still find this odd, but if everyone is going to have this change
done like this, consistency is better.

> + unsigned int n;
>
> - for (i = 0; i < 8; i++)
> - values[PIN_DATA0 + i] = !!(val & BIT(i));
> - values[PIN_CTRL_RS] = rs;
> + value_bitmap[0] = val;
> + __assign_bit(PIN_CTRL_RS, value_bitmap, rs);
> n = 9;
> if (hd->pins[PIN_CTRL_RW]) {
> - values[PIN_CTRL_RW] = 0;
> + __clear_bit(PIN_CTRL_RW, value_bitmap);
> n++;
> }
>
> /* Present the data to the port */
> - gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA0], values);
> + gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA0], value_bitmap);
>
> hd44780_strobe_gpio(hd);
> }
> @@ -83,32 +82,31 @@ static void hd44780_write_gpio8(struct hd44780 *hd, u8 val, unsigned int rs)
> /* write to an LCD panel register in 4 bit GPIO mode */
> static void hd44780_write_gpio4(struct hd44780 *hd, u8 val, unsigned int rs)
> {
> - int values[10]; /* for DATA[0-7], RS, RW, but DATA[0-3] is unused */
> - unsigned int i, n;
> + /* for DATA[0-7], RS, RW, but DATA[0-3] is unused */
> + unsigned long value_bitmap[1];

Ditto.

> + unsigned int n;
>
> /* High nibble + RS, RW */
> - for (i = 4; i < 8; i++)
> - values[PIN_DATA0 + i] = !!(val & BIT(i));
> - values[PIN_CTRL_RS] = rs;
> + value_bitmap[0] = val;
> + __assign_bit(PIN_CTRL_RS, value_bitmap, rs);
> n = 5;
> if (hd->pins[PIN_CTRL_RW]) {
> - values[PIN_CTRL_RW] = 0;
> + __clear_bit(PIN_CTRL_RW, value_bitmap);
> n++;
> }
> + value_bitmap[0] >>= PIN_DATA4;
>
> /* Present the data to the port */
> - gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4],
> - &values[PIN_DATA4]);
> + gpiod_set_array_value_cansleep(n, &hd->pins[PIN_DATA4], value_bitmap);
>
> hd44780_strobe_gpio(hd);
>
> /* Low nibble */
> - for (i = 0; i < 4; i++)
> - values[PIN_DATA4 + i] = !!(val & BIT(i));
> + value_bitmap[0] &= ~((1 << PIN_DATA4) - 1);
> + value_bitmap[0] |= val & ~((1 << PIN_DATA4) - 1);

This is still wrong! What I originally meant in my v4 review is that
there is an extra ~ in the second line.

Also, a couple of general comments:

- Please review the list of CCs (I was not CC'd originally, so maybe
there are other maintainers that aren't, either)
- In general, the new code seems harder to read than the original one
(but that is my impression).

Thanks for your effort! :-)

Cheers,
Miguel