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Date: Mon, 12 Jan 2015 11:16:17 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Benoit Parrot <bparrot@...com>
Cc: "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
Alexandre Courbot <gnurou@...il.com>,
Maxime Ripard <maxime.ripard@...e-electrons.com>,
Jiri Prchal <jiri.prchal@...ignal.cz>,
Pantelis Antoniou <panto@...oniou-consulting.com>
Subject: Re: [Patch v5 1/2] gpio: add GPIO hogging mechanism
On Fri, Dec 19, 2014 at 9:07 PM, Benoit Parrot <bparrot@...com> wrote:
> Based on Boris Brezillion's work this is a reworked patch
> of his initial GPIO hogging mechanism.
> This patch provides a way to initially configure specific GPIO
> when the GPIO controller is probed.
>
> The actual DT scanning to collect the GPIO specific data is performed
> as part of gpiochip_add().
>
> The purpose of this is to allow specific GPIOs to be configured
> without any driver specific code.
> This is particularly useful because board design are getting
> increasingly complex and given SoC pins can now have more
> than 10 mux values, a lot of connections are now dependent on
> external IO muxes to switch various modes.
>
> Specific drivers should not necessarily need to be aware of
> what accounts to a specific board implementation. This board level
> "description" should be best kept as part of the dts file.
>
> Signed-off-by: Benoit Parrot <bparrot@...com>
> Reviewed-by: Alexandre Courbot <acourbot@...dia.com>
(...)
> /**
> + * of_get_gpio_hog() - Get a GPIO hog descriptor, names and flags for GPIO API
> + * @np: device node to get GPIO from
> + * @name: GPIO line name
> + * @flags: a flags pointer to fill in
kerneldoc is unsynchronized, document both flags.
> + *
> + * Returns GPIO descriptor to use with Linux GPIO API, or one of the errno
> + * value on the error condition.
> + */
> +
No newline after kerneldoc. What is lflags and dflags?
> +static struct gpio_desc *of_get_gpio_hog(struct device_node *np,
> + const char **name,
> + enum gpio_lookup_flags *lflags,
> + enum gpiod_flags *dflags)
> +{
> + struct device_node *chip_np;
> + enum of_gpio_flags xlate_flags;
> + struct gpio_desc *desc;
> + const char *dir_val;
> + struct gg_data gg_data = {
> + .flags = &xlate_flags,
> + };
> + u32 tmp;
> + int i, ret;
> +
> + chip_np = np->parent;
> + if (!chip_np)
> + return ERR_PTR(-EINVAL);
> +
> + xlate_flags = 0;
> + *lflags = 0;
> + *dflags = 0;
> +
> + ret = of_property_read_u32(chip_np, "#gpio-cells", &tmp);
> + if (ret)
> + return ERR_PTR(ret);
> + if (tmp > MAX_PHANDLE_ARGS)
> + return ERR_PTR(-EINVAL);
> + gg_data.gpiospec.args_count = tmp;
> + gg_data.gpiospec.np = chip_np;
Are we duplicating this code elsewhere? No need to
fix now, but space for refactor later on...
> + for (i = 0; i < tmp; i++) {
> + ret = of_property_read_u32_index(np, "gpios", i,
> + &gg_data.gpiospec.args[i]);
> + if (ret)
> + return ERR_PTR(ret);
> + }
> +
> + gpiochip_find(&gg_data, of_gpiochip_find_and_xlate);
> + if (!gg_data.out_gpio) {
> + if (np->parent == np)
> + return ERR_PTR(-ENXIO);
> + else
> + return ERR_PTR(-EPROBE_DEFER);
Is this really reasonable, as we know we're instantiating the only
gpio_chip this hog can be on?
> + }
> +
> + if (xlate_flags & OF_GPIO_ACTIVE_LOW)
> + *lflags |= GPIO_ACTIVE_LOW;
> +
> + if (of_property_read_string(np, "state", &dir_val)) {
> + pr_warn("%s: GPIO:%d (%s): no hogging state specified, bailing out\n",
> + __func__, desc_to_gpio(gg_data.out_gpio), np->name);
> + return ERR_PTR(-EINVAL);
> + }
> +
> + if (!strcmp(dir_val, "input"))
> + *dflags |= GPIOD_IN;
> + else if (!strcmp(dir_val, "output-low"))
> + *dflags |= GPIOD_OUT_LOW;
> + else if (!strcmp(dir_val, "output-high"))
> + *dflags |= GPIOD_OUT_HIGH;
> + else {
> + pr_warn("%s: GPIO:%d (%s): invalid state '%s' requested, bailing out\n",
> + __func__, desc_to_gpio(gg_data.out_gpio),
> + np->name, dir_val);
> + return ERR_PTR(-EINVAL);
> + }
Hmmmm need to check the bindings first. I'm not yet sure I
like how we represent this.
> + if (name && of_property_read_string(np, "line-name", name))
> + *name = np->name;
I quite like this.
> +
> + desc = gg_data.out_gpio;
> +
> + return desc;
> +}
> +
> +/**
> + * of_gpiochip_scan_hogs - Scan gpio-controller and apply GPIO hog as requested
> + * @chip: gpio chip to act on
> + *
> + * This is only used by of_gpiochip_add to request/set GPIO initial
> + * configuration.
> + */
> +static void of_gpiochip_scan_hogs(struct gpio_chip *chip)
> +{
> + struct gpio_desc *desc = NULL;
> + struct device_node *np;
> + const char *name;
> + enum gpio_lookup_flags lflags;
> + enum gpiod_flags dflags;
> +
> + for_each_child_of_node(chip->of_node, np) {
> + if (!of_property_read_bool(np, "gpio-hog"))
> + continue;
> +
> + desc = of_get_gpio_hog(np, &name, &lflags, &dflags);
> + if (IS_ERR(desc))
> + continue;
> +
> + if (gpiod_hog(desc, name, lflags, dflags))
> + continue;
> + }
> +}
> +
> +/**
> * of_gpio_simple_xlate - translate gpio_spec to the GPIO number and flags
> * @gc: pointer to the gpio_chip structure
> * @np: device node of the GPIO chip
> @@ -302,6 +418,8 @@ void of_gpiochip_add(struct gpio_chip *chip)
>
> of_gpiochip_add_pin_range(chip);
> of_node_get(chip->of_node);
> +
> + of_gpiochip_scan_hogs(chip);
> }
>
> void of_gpiochip_remove(struct gpio_chip *chip)
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 487afe6..d79c265 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -313,6 +313,7 @@ EXPORT_SYMBOL_GPL(gpiochip_add);
>
> /* Forward-declaration */
> static void gpiochip_irqchip_remove(struct gpio_chip *gpiochip);
> +static void gpiochip_free_hogs(struct gpio_chip *chip);
>
> /**
> * gpiochip_remove() - unregister a gpio_chip
> @@ -331,6 +332,7 @@ void gpiochip_remove(struct gpio_chip *chip)
>
> gpiochip_irqchip_remove(chip);
> gpiochip_remove_pin_ranges(chip);
> + gpiochip_free_hogs(chip);
> of_gpiochip_remove(chip);
>
> for (id = 0; id < chip->ngpio; id++) {
> @@ -864,6 +866,7 @@ static bool __gpiod_free(struct gpio_desc *desc)
> clear_bit(FLAG_REQUESTED, &desc->flags);
> clear_bit(FLAG_OPEN_DRAIN, &desc->flags);
> clear_bit(FLAG_OPEN_SOURCE, &desc->flags);
> + clear_bit(FLAG_IS_HOGGED, &desc->flags);
> ret = true;
> }
>
> @@ -1836,6 +1839,47 @@ struct gpio_desc *__must_check __gpiod_get_optional(struct device *dev,
> }
> EXPORT_SYMBOL_GPL(__gpiod_get_optional);
>
> +
> +/**
> + * __gpiod_set_helper - helper function to configure a given GPIO
> + * @desc: gpio whose value will be assigned
> + * @con_id: function within the GPIO consumer
> + * @lflags: gpio_lookup_flags - returned from of_find_gpio() or
> + * of_get_gpio_hog()
> + * @dflags: gpiod_flags - optional GPIO initialization flags
> + *
> + * Return 0 on success, -ENOENT if no GPIO has been assigned to the
> + * requested function and/or index, or another IS_ERR() code if an error
> + * occurred while trying to acquire the GPIO.
> + */
> +static int __gpiod_set_helper(struct gpio_desc *desc, const char *con_id,
> + unsigned long lflags, enum gpiod_flags dflags)
This function has no sensible name.
Skip the arbitrary __ prefix and give it a descriptive name
like "gpiod_configure_flags" or something.
> +{
> + int status;
> +
> + if (lflags & GPIO_ACTIVE_LOW)
> + set_bit(FLAG_ACTIVE_LOW, &desc->flags);
> + if (lflags & GPIO_OPEN_DRAIN)
> + set_bit(FLAG_OPEN_DRAIN, &desc->flags);
> + if (lflags & GPIO_OPEN_SOURCE)
> + set_bit(FLAG_OPEN_SOURCE, &desc->flags);
> +
> + /* No particular flag request, return here... */
> + if (!(dflags & GPIOD_FLAGS_BIT_DIR_SET)) {
> + pr_debug("no flags found for %s\n", con_id);
> + return 0;
> + }
> +
> + /* Process flags */
> + if (dflags & GPIOD_FLAGS_BIT_DIR_OUT)
> + status = gpiod_direction_output(desc,
> + dflags & GPIOD_FLAGS_BIT_DIR_VAL);
> + else
> + status = gpiod_direction_input(desc);
> +
> + return status;
> +}
> +
> /**
> * gpiod_get_index - obtain a GPIO from a multi-index GPIO function
> * @dev: GPIO consumer, can be NULL for system-global GPIOs
> @@ -1885,30 +1929,12 @@ struct gpio_desc *__must_check __gpiod_get_index(struct device *dev,
> }
>
> status = gpiod_request(desc, con_id);
> -
> if (status < 0)
> return ERR_PTR(status);
>
> - if (lookupflags & GPIO_ACTIVE_LOW)
> - set_bit(FLAG_ACTIVE_LOW, &desc->flags);
> - if (lookupflags & GPIO_OPEN_DRAIN)
> - set_bit(FLAG_OPEN_DRAIN, &desc->flags);
> - if (lookupflags & GPIO_OPEN_SOURCE)
> - set_bit(FLAG_OPEN_SOURCE, &desc->flags);
> -
> - /* No particular flag request, return here... */
> - if (!(flags & GPIOD_FLAGS_BIT_DIR_SET))
> - return desc;
> -
> - /* Process flags */
> - if (flags & GPIOD_FLAGS_BIT_DIR_OUT)
> - status = gpiod_direction_output(desc,
> - flags & GPIOD_FLAGS_BIT_DIR_VAL);
> - else
> - status = gpiod_direction_input(desc);
> -
> + status = __gpiod_set_helper(desc, con_id, lookupflags, flags);
> if (status < 0) {
> - dev_dbg(dev, "setup of GPIO %s failed\n", con_id);
> + pr_debug("setup of GPIO %s failed\n", con_id);
> gpiod_put(desc);
> return ERR_PTR(status);
> }
> @@ -2002,6 +2028,68 @@ struct gpio_desc *__must_check __gpiod_get_index_optional(struct device *dev,
> EXPORT_SYMBOL_GPL(__gpiod_get_index_optional);
>
> /**
> + * gpiod_hog - Hog the specified GPIO desc given the provided flags
> + * @desc: gpio whose value will be assigned
> + * @name: gpio line name
> + * @lflags: gpio_lookup_flags - returned from of_find_gpio() or
> + * of_get_gpio_hog()
> + * @dflags: gpiod_flags - optional GPIO initialization flags
> + *
> + */
> +int gpiod_hog(struct gpio_desc *desc, const char *name,
> + unsigned long lflags, enum gpiod_flags dflags)
> +{
> + struct gpio_chip *chip;
> + struct gpio_desc *local_desc;
> + int hwnum;
> + int status;
> +
> + chip = gpiod_to_chip(desc);
> + hwnum = gpio_chip_hwgpio(desc);
> +
> + local_desc = gpiochip_request_own_desc(chip, hwnum, name);
> + if (IS_ERR(local_desc)) {
> + pr_debug("requesting own GPIO %s failed\n", name);
> + return PTR_ERR(local_desc);
> + }
> +
> + status = __gpiod_set_helper(desc, name, lflags, dflags);
> + if (status < 0) {
> + pr_debug("setup of GPIO %s failed\n", name);
> + gpiochip_free_own_desc(desc);
> + return status;
> + }
> +
> + /* Mark GPIO as hogged so it can be identified and removed later */
> + set_bit(FLAG_IS_HOGGED, &desc->flags);
> +
> + pr_debug("%s: GPIO:%d (%s) as %s%s\n", __func__,
Convert to pr_info(), as this *should* be printed to console, skip printing
__func__ please.
Modify string to "GPIO line %d (%s) hogged as %s%s\n"
> + desc_to_gpio(desc), name,
> + (dflags&GPIOD_FLAGS_BIT_DIR_OUT) ? "output" : "input",
> + (dflags&GPIOD_FLAGS_BIT_DIR_OUT) ?
> + (dflags&GPIOD_FLAGS_BIT_DIR_VAL) ? "/high" : "/low":"");
> +
> + return 0;
> +}
> +
> +/**
> + * gpiochip_free_hogs - Scan gpio-controller chip and release GPIO hog
> + * @chip: gpio chip to act on
> + *
> + * This is only used by of_gpiochip_remove to free hogged gpios
> + *
Skip this comment newline.
Overall the changes to gpiolib.c looks very nice.
Yours,
Linus Walleij
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