linux-kernel - Re: [PATCH 1/4] gpiolib: Add gpiochip_find_by_name() and gpio_find_by_chip

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Date:	Thu, 8 Mar 2012 18:09:36 -0800
From:	Tony Lindgren <tony@...mide.com>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	linux-kernel@...r.kernel.org,
	Linus Walleij <linus.walleij@...ricsson.com>,
	Arnd Bergmann <arnd@...db.de>, Rajendra Nayak <rnayak@...com>,
	linux-mmc@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/4] gpiolib: Add gpiochip_find_by_name() and
 gpio_find_by_chip_name()

* Grant Likely <grant.likely@...retlab.ca> [120308 17:08]:
> On Fri, 2 Mar 2012 11:06:15 -0800, Tony Lindgren <tony@...mide.com> wrote:
> > 
> > Want to do that as a separate patch or want me to fold it in?
> 
> I've got it as a separate commit in my gpio/next branch.

OK great, below is my patch updated against gpio/next if you
want to pick it up.

Regards,

Tony


From: Tony Lindgren <tony@...mide.com>
Date: Fri, 2 Mar 2012 11:30:23 -0800
Subject: [PATCH] gpiolib: Add gpiochip_find_by_name() and gpio_find_by_chip_name()

Currently there is no way for drivers to request a GPIO on a particular
gpio chip using platform data. This makes it hard to support multiple
GPIO controllers with platform driver with dynamic GPIO and interrupt
numbering, such as with CONFIG_SPARSE_IRQ.

Let's make it easier for platform device drivers to find GPIOs on a
specific gpio_chip by adding two functions: gpiochip_find_by_name()
and gpio_find_by_chip_name().

Note that these functions should not be used with device tree as
pointed out by Grant Likely <grant.likely@...retlab.ca> as the names
are instantiated from device tree.

As gpiochip_find() is already exported, we may as well export
gpiochip_find_by_name() too.

Cc: Grant Likely <grant.likely@...retlab.ca>
Cc: Linus Walleij <linus.walleij@...ricsson.com>
Cc: Arnd Bergmann <arnd@...db.de>
Cc: Rajendra Nayak <rnayak@...com>
Signed-off-by: Tony Lindgren <tony@...mide.com>

--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1178,6 +1178,51 @@ struct gpio_chip *gpiochip_find(const void *data,
 }
 EXPORT_SYMBOL_GPL(gpiochip_find);
 
+static int gpiochip_match_name(struct gpio_chip *chip, const void *name)
+{
+	return !strcmp(name, chip->label);
+}
+
+/**
+ * gpiochip_find_by_name() - iterator for locating a gpio_chip by name
+ * @name: name of the gpio_chip
+ *
+ * Similar to bus_find_device_by_name. It returns a reference to the
+ * first gpio_chip with matching name. It ignores NULL and empty names.
+ * If you need to do something more complex, then use gpiochip_find.
+ */
+struct gpio_chip *gpiochip_find_by_name(const char *name)
+{
+	if (!name || !strcmp(name, ""))
+		return NULL;
+
+	return gpiochip_find(name, gpiochip_match_name);
+}
+EXPORT_SYMBOL_GPL(gpiochip_find_by_name);
+
+/**
+ * gpio_find_by_chip_name() - find a gpio on a specific gpio_chip
+ * @chip_name: name of the gpio_chip
+ * @gpio_offset: offset of the gpio on the gpio_chip
+ *
+ * Note that gpiochip_find_by_name returns the first matching
+ * gpio_chip name. For more complex matching, see gpio_find.
+ */
+int gpio_find_by_chip_name(const char *chip_name, unsigned gpio_offset)
+{
+	struct gpio_chip *chip;
+	int gpio;
+
+	chip = gpiochip_find_by_name(chip_name);
+	if (!chip)
+		return -ENODEV;
+
+	gpio = chip->base + gpio_offset;
+
+	return gpio;
+}
+EXPORT_SYMBOL_GPL(gpio_find_by_chip_name);
+
 /* These "optional" allocation calls help prevent drivers from stomping
  * on each other, and help provide better diagnostics in debugfs.
  * They're called even less than the "set direction" calls.
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -145,7 +145,8 @@ extern int __must_check gpiochip_remove(struct gpio_chip *chip);
 extern struct gpio_chip *gpiochip_find(const void *data,
 					int (*match)(struct gpio_chip *chip,
 						     const void *data));
-
+extern struct gpio_chip *gpiochip_find_by_name(const char *name);
+extern int gpio_find_by_chip_name(const char *chip_name, unsigned gpio_offset);
 
 /* Always use the library code for GPIO management calls,
  * or when sleeping may be involved.
--
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