usb/gadget: Replace the old USB audio FU definitions in f_audio.c

[safe/jmp/linux-2.6] / Documentation / gpio.txt

diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
index fa4dc07..c2c6e9b 100644 (file)
--- a/Documentation/gpio.txt
+++ b/Documentation/gpio.txt
@@ -253,6 +253,70 @@ pin setup (e.g. controlling which pin the GPIO uses, pullup/pulldown).
 Also note that it's your responsibility to have stopped using a GPIO
 before you free it.
 
 Also note that it's your responsibility to have stopped using a GPIO
 before you free it.
 

+Considering in most cases GPIOs are actually configured right after they
+are claimed, three additional calls are defined:
+
+       /* request a single GPIO, with initial configuration specified by
+        * 'flags', identical to gpio_request() wrt other arguments and
+        * return value
+        */
+       int gpio_request_one(unsigned gpio, unsigned long flags, const char *label);
+
+       /* request multiple GPIOs in a single call
+        */
+       int gpio_request_array(struct gpio *array, size_t num);
+
+       /* release multiple GPIOs in a single call
+        */
+       void gpio_free_array(struct gpio *array, size_t num);
+
+where 'flags' is currently defined to specify the following properties:
+
+       * GPIOF_DIR_IN          - to configure direction as input
+       * GPIOF_DIR_OUT         - to configure direction as output
+
+       * GPIOF_INIT_LOW        - as output, set initial level to LOW
+       * GPIOF_INIT_HIGH       - as output, set initial level to HIGH
+
+since GPIOF_INIT_* are only valid when configured as output, so group valid
+combinations as:
+
+       * GPIOF_IN              - configure as input
+       * GPIOF_OUT_INIT_LOW    - configured as output, initial level LOW
+       * GPIOF_OUT_INIT_HIGH   - configured as output, initial level HIGH
+
+In the future, these flags can be extended to support more properties such
+as open-drain status.
+
+Further more, to ease the claim/release of multiple GPIOs, 'struct gpio' is
+introduced to encapsulate all three fields as:
+
+       struct gpio {
+               unsigned        gpio;
+               unsigned long   flags;
+               const char      *label;
+       };
+
+A typical example of usage:
+
+       static struct gpio leds_gpios[] = {
+               { 32, GPIOF_OUT_INIT_HIGH, "Power LED" }, /* default to ON */
+               { 33, GPIOF_OUT_INIT_LOW,  "Green LED" }, /* default to OFF */
+               { 34, GPIOF_OUT_INIT_LOW,  "Red LED"   }, /* default to OFF */
+               { 35, GPIOF_OUT_INIT_LOW,  "Blue LED"  }, /* default to OFF */
+               { ... },
+       };
+
+       err = gpio_request_one(31, GPIOF_IN, "Reset Button");
+       if (err)
+               ...
+
+       err = gpio_request_array(leds_gpios, ARRAY_SIZE(leds_gpios));
+       if (err)
+               ...
+
+       gpio_free_array(leds_gpios, ARRAY_SIZE(leds_gpios));
+

 
 GPIOs mapped to IRQs
 --------------------
 
 GPIOs mapped to IRQs
 --------------------


@@ -380,7 +444,7 @@ rare; use gpiochip_remove() when it is unavoidable.
 
 Most often a gpio_chip is part of an instance-specific structure with state
 not exposed by the GPIO interfaces, such as addressing, power management,
 
 Most often a gpio_chip is part of an instance-specific structure with state
 not exposed by the GPIO interfaces, such as addressing, power management,

-and more.  Chips such as codecs will have complex non-GPIO state,
+and more.  Chips such as codecs will have complex non-GPIO state.

 
 Any debugfs dump method should normally ignore signals which haven't been
 requested as GPIOs.  They can use gpiochip_is_requested(), which returns
 
 Any debugfs dump method should normally ignore signals which haven't been
 requested as GPIOs.  They can use gpiochip_is_requested(), which returns


@@ -531,7 +595,14 @@ and have the following read/write attributes:
                This file exists only if the pin can be configured as an
                interrupt generating input pin.
 
                This file exists only if the pin can be configured as an
                interrupt generating input pin.
 

-GPIO controllers have paths like /sys/class/gpio/chipchip42/ (for the
+       "active_low" ... reads as either 0 (false) or 1 (true).  Write
+               any nonzero value to invert the value attribute both
+               for reading and writing.  Existing and subsequent
+               poll(2) support configuration via the edge attribute
+               for "rising" and "falling" edges will follow this
+               setting.
+
+GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the

 controller implementing GPIOs starting at #42) and have the following
 read-only attributes:
 
 controller implementing GPIOs starting at #42) and have the following
 read-only attributes:
 


@@ -566,6 +637,8 @@ requested using gpio_request():
        int gpio_export_link(struct device *dev, const char *name,
                unsigned gpio)
 
        int gpio_export_link(struct device *dev, const char *name,
                unsigned gpio)
 

+       /* change the polarity of a GPIO node in sysfs */
+       int gpio_sysfs_set_active_low(unsigned gpio, int value);

 
 After a kernel driver requests a GPIO, it may only be made available in
 the sysfs interface by gpio_export().  The driver can control whether the
 
 After a kernel driver requests a GPIO, it may only be made available in
 the sysfs interface by gpio_export().  The driver can control whether the


@@ -580,3 +653,9 @@ After the GPIO has been exported, gpio_export_link() allows creating
 symlinks from elsewhere in sysfs to the GPIO sysfs node.  Drivers can
 use this to provide the interface under their own device in sysfs with
 a descriptive name.
 symlinks from elsewhere in sysfs to the GPIO sysfs node.  Drivers can
 use this to provide the interface under their own device in sysfs with
 a descriptive name.

+
+Drivers can use gpio_sysfs_set_active_low() to hide GPIO line polarity
+differences between boards from user space.  This only affects the
+sysfs interface.  Polarity change can be done both before and after
+gpio_export(), and previously enabled poll(2) support for either
+rising or falling edge will be reconfigured to follow this setting.