Re: [PATCH] gpiolib: Use seq_file's iterator interface

Grant Likely
2012-05-11T23:48:59Z

On Thu, 12 Apr 2012 13:26:01 +0200, Thierry Reding <thierry.reding@avionic-design.de> wrote:
> When dumping a collection of items via seq_file, it is recommended to
> use the iterator interface. For the gpiolib debugfs interface this can
> be done to dump each GPIO chip in turn.
>
> Note that for gpiolib this is a little cumbersome because it does not
> provide a list of registered GPIO chips and the only way to iterate is
> over each GPIO individually. Once a chip is found, the number of GPIOs
> it provides can be skipped as a small optimization.
>
> This patch was requested by Arnd Bergmann here:
>
> http://article.gmane.org/gmane.linux.ports.tegra/3535
>
> Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>

Arnd, you requested this. Can you review it?

Thanks,
g.

> Cc: Linus Walleij <linus.walleij@stericsson.com>
> Cc: Grant Likely <grant.likely@secretlab.ca>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: linux-kernel@vger.kernel.org
> ---
> drivers/gpio/gpiolib.c | 102 +++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 74 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 566d012..3c5296f 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1773,56 +1773,102 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip)
> }
> }
>
> -static int gpiolib_show(struct seq_file *s, void *unused)
> +static void *gpiolib_seq_start(struct seq_file *s, loff_t *pos)
> {
> - struct gpio_chip *chip = NULL;
> - unsigned gpio;
> - int started = 0;
> + struct gpio_chip *chip = NULL;
> + unsigned int gpio;
> + void *ret = NULL;
> + loff_t index = 0;
>
> /* REVISIT this isn't locked against gpio_chip removal ... */
>
> for (gpio = 0; gpio_is_valid(gpio); gpio++) {
> - struct device *dev;
> -
> - if (chip == gpio_desc[gpio].chip)
> + if (gpio_desc[gpio].chip == chip)
> continue;
> +
> chip = gpio_desc[gpio].chip;
> if (!chip)
> continue;
>
> - seq_printf(s, "%sGPIOs %d-%d",
> - started ? "\n" : "",
> - chip->base, chip->base + chip->ngpio - 1);
> - dev = chip->dev;
> - if (dev)
> - seq_printf(s, ", %s/%s",
> - dev->bus ? dev->bus->name : "no-bus",
> - dev_name(dev));
> - if (chip->label)
> - seq_printf(s, ", %s", chip->label);
> - if (chip->can_sleep)
> - seq_printf(s, ", can sleep");
> - seq_printf(s, ":\n");
> -
> - started = 1;
> - if (chip->dbg_show)
> - chip->dbg_show(s, chip);
> - else
> - gpiolib_dbg_show(s, chip);
> + if (index++ >= *pos) {
> + ret = chip;
> + break;
> + }
> }
> +
> + s->private = "";
> +
> + return ret;
> +}
> +
> +static void *gpiolib_seq_next(struct seq_file *s, void *v, loff_t *pos)
> +{
> + struct gpio_chip *chip = v;
> + unsigned int gpio;
> + void *ret = NULL;
> +
> + /* skip GPIOs provided by the current chip */
> + for (gpio = chip->base + chip->ngpio; gpio_is_valid(gpio); gpio++) {
> + chip = gpio_desc[gpio].chip;
> + if (chip) {
> + ret = chip;
> + break;
> + }
> + }
> +
> + s->private = "\n";
> + ++*pos;
> +
> + return ret;
> +}
> +
> +static void gpiolib_seq_stop(struct seq_file *s, void *v)
> +{
> +}
> +
> +static int gpiolib_seq_show(struct seq_file *s, void *v)
> +{
> + struct gpio_chip *chip = v;
> + struct device *dev;
> +
> + seq_printf(s, "%sGPIOs %d-%d", (char *)s->private,
> + chip->base, chip->base + chip->ngpio - 1);
> + dev = chip->dev;
> + if (dev)
> + seq_printf(s, ", %s/%s", dev->bus ? dev->bus->name : "no-bus",
> + dev_name(dev));
> + if (chip->label)
> + seq_printf(s, ", %s", chip->label);
> + if (chip->can_sleep)
> + seq_printf(s, ", can sleep");
> + seq_printf(s, ":\n");
> +
> + if (chip->dbg_show)
> + chip->dbg_show(s, chip);
> + else
> + gpiolib_dbg_show(s, chip);
> +
> return 0;
> }
>
> +static const struct seq_operations gpiolib_seq_ops = {
> + .start = gpiolib_seq_start,
> + .next = gpiolib_seq_next,
> + .stop = gpiolib_seq_stop,
> + .show = gpiolib_seq_show,
> +};
> +
> static int gpiolib_open(struct inode *inode, struct file *file)
> {
> - return single_open(file, gpiolib_show, NULL);
> + return seq_open(file, &gpiolib_seq_ops);
> }
>
> static const struct file_operations gpiolib_operations = {
> + .owner = THIS_MODULE,
> .open = gpiolib_open,
> .read = seq_read,
> .llseek = seq_lseek,
> - .release = single_release,
> + .release = seq_release,
> };
>
> static int __init gpiolib_debugfs_init(void)
> --
> 1.7.10
>

--
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.