[PATCH] gpiolib: Use seq_file's iterator interface

Thierry Reding
2012-04-12T11:57:29Z

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>
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