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Message-ID: <CAHp75Vdr8hVBU9x1U2s7K_fp773YqeRpM4bPFaYWKeTSp9qV7w@mail.gmail.com>
Date: Mon, 2 Dec 2013 13:49:43 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Alexandre Courbot <acourbot@...dia.com>
Cc: Linus Walleij <linus.walleij@...aro.org>,
Mika Westerberg <mika.westerberg@...ux.intel.com>,
Rhyland Klein <rklein@...dia.com>,
Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] gpio: better lookup method for platform GPIOs
On Mon, Dec 2, 2013 at 1:01 PM, Alexandre Courbot <acourbot@...dia.com> wrote:
> Change the format of the platform GPIO lookup tables to make them less
> confusing and improve lookup efficiency.
>
> The previous format was a single linked-list that required to compare
> the device name and function ID of every single GPIO defined for each
> lookup. Switch that to a list of per-device tables, so that the lookup
> can be done in two steps, omitting the GPIOs that are not relevant for a
> particular device.
>
> The matching rules are now defined as follows:
> - The device name must match *exactly*, and can be NULL for GPIOs not
> assigned to a particular device,
> - If the function ID in the lookup table is NULL, the con_id argument of
> gpiod_get() will not be used for lookup. However, if it is defined, it
> must match exactly.
> - The index must always match.
Thanks for an updated version.
Few minor comments below.
Comments about loops are here as well.
I any case:
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
>
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> Acked-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> ---
> Changes since v1:
> - Applied most fixes suggested by Andy
> - Hopefully safer and less confusing table lookup algorithm
> - Added Mika's ack
>
> Documentation/gpio/board.txt | 25 ++++++----
> drivers/gpio/gpiolib.c | 109 +++++++++++++++++++++++--------------------
> include/linux/gpio/driver.h | 22 ++++-----
> 3 files changed, 85 insertions(+), 71 deletions(-)
>
> diff --git a/Documentation/gpio/board.txt b/Documentation/gpio/board.txt
> index 0d03506f2cc5..a4fdd96cef93 100644
> --- a/Documentation/gpio/board.txt
> +++ b/Documentation/gpio/board.txt
> @@ -72,10 +72,11 @@ where
>
> - chip_label is the label of the gpiod_chip instance providing the GPIO
> - chip_hwnum is the hardware number of the GPIO within the chip
> - - dev_id is the identifier of the device that will make use of this GPIO. If
> - NULL, the GPIO will be available to all devices.
> + - dev_id is the identifier of the device that will make use of this GPIO. It
> + can be NULL, in which case it will be matched for calls to gpiod_get()
> + with a NULL device.
> - con_id is the name of the GPIO function from the device point of view. It
> - can be NULL.
> + can be NULL, in which case it will match any function.
> - idx is the index of the GPIO within the function.
> - flags is defined to specify the following properties:
> * GPIOF_ACTIVE_LOW - to configure the GPIO as active-low
> @@ -88,16 +89,20 @@ Note that GPIO_LOOKUP() is just a shortcut to GPIO_LOOKUP_IDX() where idx = 0.
>
> A lookup table can then be defined as follows:
>
> - struct gpiod_lookup gpios_table[] = {
> - GPIO_LOOKUP_IDX("gpio.0", 15, "foo.0", "led", 0, GPIO_ACTIVE_HIGH),
> - GPIO_LOOKUP_IDX("gpio.0", 16, "foo.0", "led", 1, GPIO_ACTIVE_HIGH),
> - GPIO_LOOKUP_IDX("gpio.0", 17, "foo.0", "led", 2, GPIO_ACTIVE_HIGH),
> - GPIO_LOOKUP("gpio.0", 1, "foo.0", "power", GPIO_ACTIVE_LOW),
> - };
> +struct gpiod_lookup_table gpios_table = {
> + .dev_id = "foo.0",
> + .size = 4,
> + .table = {
> + GPIO_LOOKUP_IDX("gpio.0", 15, "led", 0, GPIO_ACTIVE_HIGH),
> + GPIO_LOOKUP_IDX("gpio.0", 16, "led", 1, GPIO_ACTIVE_HIGH),
> + GPIO_LOOKUP_IDX("gpio.0", 17, "led", 2, GPIO_ACTIVE_HIGH),
> + GPIO_LOOKUP("gpio.0", 1, "power", GPIO_ACTIVE_LOW),
> + },
> +};
>
> And the table can be added by the board code as follows:
>
> - gpiod_add_table(gpios_table, ARRAY_SIZE(gpios_table));
> + gpiod_add_lookup_table(&gpios_table);
>
> The driver controlling "foo.0" will then be able to obtain its GPIOs as follows:
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index f72618ba716a..d17d6eabed6a 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -2259,18 +2259,14 @@ void gpiod_set_value_cansleep(struct gpio_desc *desc, int value)
> EXPORT_SYMBOL_GPL(gpiod_set_value_cansleep);
>
> /**
> - * gpiod_add_table() - register GPIO device consumers
> - * @table: array of consumers to register
> - * @num: number of consumers in table
> + * gpiod_add_lookup_table() - register GPIO device consumers
> + * @table: table of consumers to register
> */
> -void gpiod_add_table(struct gpiod_lookup *table, size_t size)
> +void gpiod_add_lookup_table(struct gpiod_lookup_table *table)
> {
> mutex_lock(&gpio_lookup_lock);
>
> - while (size--) {
> - list_add_tail(&table->list, &gpio_lookup_list);
> - table++;
> - }
> + list_add_tail(&table->list, &gpio_lookup_list);
>
> mutex_unlock(&gpio_lookup_lock);
> }
> @@ -2326,72 +2322,85 @@ static struct gpio_desc *acpi_find_gpio(struct device *dev, const char *con_id,
> return desc;
> }
>
> -static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,
> - unsigned int idx,
> - enum gpio_lookup_flags *flags)
> +static struct gpiod_lookup_table *gpiod_find_lookup_table(struct device *dev)
> {
> const char *dev_id = dev ? dev_name(dev) : NULL;
> - struct gpio_desc *desc = ERR_PTR(-ENODEV);
> - unsigned int match, best = 0;
> - struct gpiod_lookup *p;
> + struct gpiod_lookup_table *table;
>
> mutex_lock(&gpio_lookup_lock);
>
> - list_for_each_entry(p, &gpio_lookup_list, list) {
> - match = 0;
> + list_for_each_entry(table, &gpio_lookup_list, list) {
> + if (table->dev_id && dev_id) {
> + /*
> + * Valid strings on both ends, must be identical to have
> + * a match
> + */
> + if (!strcmp(table->dev_id, dev_id))
> + goto end;
> + } else {
> + /*
> + * One of the pointers is NULL, so both must be to have
> + * a match
> + */
> + if (dev_id == table->dev_id)
> + goto end;
> + }
Yes, in this case it looks clearer. Though, you might join last else
and if in one line.
> + }
> + table = NULL;
Up to you, though I think it's clearer to return NULL explicitly (and
unlock mutex before).
>
> - if (p->dev_id) {
> - if (!dev_id || strcmp(p->dev_id, dev_id))
> - continue;
> +end:
Maybe 'found' suits better?
> + mutex_unlock(&gpio_lookup_lock);
> + return table;
> +}
>
> - match += 2;
> - }
> +static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id,
> + unsigned int idx,
> + enum gpio_lookup_flags *flags)
> +{
> + struct gpio_desc *desc = ERR_PTR(-ENODEV);
> + struct gpiod_lookup_table *table;
> + int i;
>
> - if (p->con_id) {
> - if (!con_id || strcmp(p->con_id, con_id))
> - continue;
> + table = gpiod_find_lookup_table(dev);
> + if (!table)
> + return desc;
>
> - match += 1;
> - }
> + for (i = 0; i < table->size; i++) {
> + struct gpio_chip *chip;
> + struct gpiod_lookup *p = &table->table[i];
>
> + /* idx must always match exactly */
> if (p->idx != idx)
> continue;
>
> - if (match > best) {
> - struct gpio_chip *chip;
> -
> - chip = find_chip_by_name(p->chip_label);
> -
> - if (!chip) {
> - dev_warn(dev, "cannot find GPIO chip %s\n",
> - p->chip_label);
> - continue;
> - }
> + /* If the lookup entry has a con_id, require exact match */
> + if (p->con_id && (!con_id || strcmp(p->con_id, con_id)))
> + continue;
>
> - if (chip->ngpio <= p->chip_hwnum) {
> - dev_warn(dev, "GPIO chip %s has %d GPIOs\n",
> - chip->label, chip->ngpio);
> - continue;
> - }
> + chip = find_chip_by_name(p->chip_label);
>
> - desc = gpio_to_desc(chip->base + p->chip_hwnum);
> - *flags = p->flags;
> + if (!chip) {
> + dev_warn(dev, "cannot find GPIO chip %s\n",
> + p->chip_label);
Could it be one line?
> + continue;
> + }
>
> - if (match != 3)
> - best = match;
> - else
> - break;
> + if (chip->ngpio <= p->chip_hwnum) {
> + dev_warn(dev, "GPIO chip %s has %d GPIOs\n",
> + chip->label, chip->ngpio);
> + continue;
> }
> - }
>
> - mutex_unlock(&gpio_lookup_lock);
> + desc = gpiochip_offset_to_desc(chip, p->chip_hwnum);
> + *flags = p->flags;
> + }
>
> return desc;
> }
>
> /**
> * gpio_get - obtain a GPIO for a given GPIO function
> - * @dev: GPIO consumer
> + * @dev: GPIO consumer, can be NULL for system-global GPIOs
> * @con_id: function within the GPIO consumer
> *
> * Return the GPIO descriptor corresponding to the function con_id of device
> diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
> index 3ea2cf6b0e6c..44893ef40817 100644
> --- a/include/linux/gpio/driver.h
> +++ b/include/linux/gpio/driver.h
> @@ -140,7 +140,6 @@ enum gpio_lookup_flags {
> * platform data.
> */
> struct gpiod_lookup {
> - struct list_head list;
> /*
> * name of the chip the GPIO belongs to
> */
> @@ -150,10 +149,6 @@ struct gpiod_lookup {
> */
> u16 chip_hwnum;
> /*
> - * name of device that can claim this GPIO
> - */
> - const char *dev_id;
> - /*
> * name of the GPIO from the device's point of view
> */
> const char *con_id;
> @@ -167,28 +162,33 @@ struct gpiod_lookup {
> enum gpio_lookup_flags flags;
> };
>
> +struct gpiod_lookup_table {
> + struct list_head list;
> + const char *dev_id;
> + unsigned int size;
> + struct gpiod_lookup table[];
> +};
> +
> /*
> * Simple definition of a single GPIO under a con_id
> */
> -#define GPIO_LOOKUP(_chip_label, _chip_hwnum, _dev_id, _con_id, _flags) \
> - GPIO_LOOKUP_IDX(_chip_label, _chip_hwnum, _dev_id, _con_id, 0, _flags)
> +#define GPIO_LOOKUP(_chip_label, _chip_hwnum, _con_id, _flags) \
> + GPIO_LOOKUP_IDX(_chip_label, _chip_hwnum, _con_id, 0, _flags)
>
> /*
> * Use this macro if you need to have several GPIOs under the same con_id.
> * Each GPIO needs to use a different index and can be accessed using
> * gpiod_get_index()
> */
> -#define GPIO_LOOKUP_IDX(_chip_label, _chip_hwnum, _dev_id, _con_id, _idx, \
> - _flags) \
> +#define GPIO_LOOKUP_IDX(_chip_label, _chip_hwnum, _con_id, _idx, _flags) \
> { \
> .chip_label = _chip_label, \
> .chip_hwnum = _chip_hwnum, \
> - .dev_id = _dev_id, \
> .con_id = _con_id, \
> .idx = _idx, \
> .flags = _flags, \
> }
>
> -void gpiod_add_table(struct gpiod_lookup *table, size_t size);
> +void gpiod_add_lookup_table(struct gpiod_lookup_table *table);
>
> #endif
> --
> 1.8.4.2
>
--
With Best Regards,
Andy Shevchenko
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