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Date: Thu, 28 Nov 2013 17:54:47 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Alexandre Courbot <acourbot@...dia.com>
Cc: Linus Walleij <linus.walleij@...aro.org>,
Rhyland Klein <rklein@...dia.com>,
Mika Westerberg <mika.westerberg@...ux.intel.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] gpio: better lookup method for platform GPIOs
On Thu, Nov 28, 2013 at 10:46 AM, 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 that, since I'm also was a bit confused of those dev_id/con_id stuff.
Few comments below (mostly about style).
> --- a/Documentation/gpio/board.txt
> +++ b/Documentation/gpio/board.txt
> @@ -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),
Can you use deeper indentation for GPIO_* lines here?
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -2326,72 +2322,77 @@ 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 && strcmp(table->dev_id, dev_id))
Maybe check !dev_id outside of loop?
> + continue;
>
> - if (p->dev_id) {
> - if (!dev_id || strcmp(p->dev_id, dev_id))
> - continue;
> + if (dev_id != table->dev_id)
> + continue;
>
> - match += 2;
> - }
> + return table;
What about
if (dev_id == table->dev_id)
return table;
?
> + }
>
> - if (p->con_id) {
> - if (!con_id || strcmp(p->con_id, con_id))
> - continue;
> + mutex_unlock(&gpio_lookup_lock);
>
> - match += 1;
> - }
> + return NULL;
> +}
>
> - if (p->idx != idx)
> - continue;
> +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 (match > best) {
> - struct gpio_chip *chip;
>
Looks like redundant empty line.
> - chip = find_chip_by_name(p->chip_label);
> + table = gpiod_find_lookup_table(dev);
> + if (!table)
> + return desc;
>
> - if (!chip) {
> - dev_warn(dev, "cannot find GPIO chip %s\n",
> - p->chip_label);
> - continue;
> - }
> + for (i = 0; i < table->size; i++) {
> + struct gpio_chip *chip;
> + struct gpiod_lookup *p = &table->table[i];
>
> - if (chip->ngpio <= p->chip_hwnum) {
> - dev_warn(dev, "GPIO chip %s has %d GPIOs\n",
> - chip->label, chip->ngpio);
> + if (p->idx != idx)
> + continue;
> +
> + if (p->con_id) {
> + if (!con_id || strcmp(p->con_id, con_id))
Could be one 'if' and moreover !con_id check might be outside a loop.
> continue;
> - }
> + }
>
> - desc = gpio_to_desc(chip->base + p->chip_hwnum);
> - *flags = p->flags;
> + chip = find_chip_by_name(p->chip_label);
>
> - if (match != 3)
> - best = match;
> - else
> - break;
> + if (!chip) {
> + dev_warn(dev, "cannot find GPIO chip %s\n",
> + p->chip_label);
> + continue;
> }
> - }
>
> - mutex_unlock(&gpio_lookup_lock);
> + if (chip->ngpio <= p->chip_hwnum) {
> + dev_warn(dev, "GPIO chip %s has %d GPIOs\n",
> + chip->label, chip->ngpio);
> + continue;
> + }
> +
> + desc = gpiochip_offset_to_desc(chip, p->chip_hwnum);
> + *flags = p->flags;
> + }
>
> return desc;
> }
--
With Best Regards,
Andy Shevchenko
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