Merge tag 'gpio-v4.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio

Pull GPIO updates from Linus Walleij:
 "This is the bulk of GPIO changes for the v4.3 kernel cycle.

  There is quite a lot going on in the GPIO subsystem this merge window,
  so the main matter is decribed below.

  The hits in other subsystems when making the GPIO flags optional are
  all ACKed by their respective subsystem maintainers.

  Core changes:

   - Root out the wrapper devm_gpiod_get() and gpiod_get() etc versions
     of the descriptor calls that did not use the flags argument on the
     end.  This was around for too long and eventually Uwe Kleine-König
     took the time to clean it out and the last users are removed along
     with the macros in this tag.  In several cases the use of flags
     simplifies the code.  For this reason we have (ACKed) patches
     hitting in DRM, IIO, media, NFC, USB+PHY up until we hammer in the
     nail with removing the macros.

   - Add a fat document describing how much ready-made GPIO stuff we
     have i the kernel to discourage people from reinventing a square
     wheel in userspace, as so often happens.

   - Create a separate lockdep class for each instance of a GPIO IRQ
     chip instead of using one class for all chips, as the current code
     will not work with systems with several GPIO chips doing lockdep
     debugging.

   - Protect against driver unloading also when a GPIO line is only used
     as IRQ for the GPIOLIB_IRQCHIP helpers.

   - If the GPIO chip has no designated owner, assign the parent device
     driver owner as owner.

   - Consolidation of chained IRQ handler install/remove replacing all
     call sites where irq_set_handler_data() and
     irq_set_chained_handler() were done in succession with a combined
     call to irq_set_chained_handler_and_data().

     This series was created by Thomas Gleixner after the problem was
     observed by Russell King.

   - Tglx also made another series of patches switching
     __irq_set_handler_locked() for irq_set_handler_locked() which is
     way cleaner.

   - Tglx and Jiang Liu wrote a good bunch of patches to make use of
     irq_desc_get_xxx() accessors and avoid looking up irq_descs from
     IRQ numbers.  The goal is to get rid of the irq number from the
     handlers in the IRQ flow which is nice.

   - Rob Herring killed off the set_irq_flags() for all GPIO drivers.
     This was an ARM specific function that is replaced with the generic
     irq_modify_status() where special flags are actually needed.

   - When an OF node has a pin range for its GPIOs, return -EPROBE_DEFER
     if the pin controller isn't available.  Pretty logical, yet needed
     to be fixed.

   - If a driver using GPIOLIB_IRQCHIP has its own irq_*_resources call
     back, then call these instead of the defaults provided by the
     GPIOLIB.

   - Fix an undocumented ABI hole: named GPIOs were not properly
     documented.

  Driver improvements:

   - Add get_direction() support to the generic GPIO driver, it's
     strange that we didn't have that before.

   - Make it possible to have input-only GPIO chips using the generic
     GPIO driver.

   - Clean out platform data support from the Emma Mobile (EM) driver

   - Finegrained runtime PM support for the RCAR driver.

   - Support r8a7795 (R-car H3) in the RCAR driver.

   - Support interrupts on GPIOs 16 thru 31 in the DaVinci driver.

   - Some consolidation and new support in the MPC8xxx driver, we now
     support MPC5125.

   - Preempt-RT-friendly patches: the OMAP, MPC8xxx, drivers uses raw
     spinlocks making it work better with the realime patches.

   - Interrupt support for the EXTRAXFS GPIO driver.

   - Make the ETRAXFS GPIO driver support also ARTPEC-3.

   - Interrupt and wakeup support for the BRCMSTB driver, also for
     wakeup from S5 cold boot.

   - Mask MXC IRQs during suspend.

   - Improve OMAP2 GPIO set_debounce() to work according to spec.

   - The VF610 driver handles IRQs properly.

  New drivers:

   - ZTE ZX GPIO driver"

* tag 'gpio-v4.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio: (87 commits)
  Revert "gpio: extraxfs: fix returnvar.cocci warnings"
  gpio: tc3589x: use static container helper
  gpio: xlp: fix error return code
  gpio: vf610: handle level IRQ's properly
  gpio: max732x: Fix error handling in probe()
  gpio: omap: fix clk_prepare/unprepare usage
  gpio: omap: protect regs access in omap_gpio_irq_handler
  gpio: omap: fix omap2_set_gpio_debounce
  gpio: omap: switch to use platform_get_irq
  gpio: omap: remove wrong irq_domain_remove usage in probe
  gpiolib: add description for gpio irqchip fields in struct gpio_chip
  gpio: extraxfs: fix returnvar.cocci warnings
  gpiolib: irqchip: use different lockdep class for each gpio irqchip
  gpio/grgpio: fix deadlock in grgpio_irq_unmap()
  Documentation: gpio: consumer: describe active low property
  gpio: mxc: fix section mismatch warning
  gpio/mxc: mask gpio interrupts in suspend
  gpio: omap: Fix missing raw locks conversion
  gpio: brcmstb: support wakeup from S5 cold boot
  gpio: brcmstb: Add interrupt and wakeup source support
  ...

1 files changed, 95 insertions, 0 deletions

diff --git a/Documentation/gpio/drivers-on-gpio.txt b/Documentation/gpio/drivers-on-gpio.txt
new file mode 100644
index 000000000000..f6121328630f
--- /dev/null
+++ b/Documentation/gpio/drivers-on-gpio.txt
@@ -0,0 +1,95 @@
+Subsystem drivers using GPIO
+============================
+
+Note that standard kernel drivers exist for common GPIO tasks and will provide
+the right in-kernel and userspace APIs/ABIs for the job, and that these
+drivers can quite easily interconnect with other kernel subsystems using
+hardware descriptions such as device tree or ACPI:
+
+- leds-gpio: drivers/leds/leds-gpio.c will handle LEDs connected to  GPIO
+  lines, giving you the LED sysfs interface
+
+- ledtrig-gpio: drivers/leds/trigger/ledtrig-gpio.c will provide a LED trigger,
+  i.e. a LED will turn on/off in response to a GPIO line going high or low
+  (and that LED may in turn use the leds-gpio as per above).
+
+- gpio-keys: drivers/input/keyboard/gpio_keys.c is used when your GPIO line
+  can generate interrupts in response to a key press. Also supports debounce.
+
+- gpio-keys-polled: drivers/input/keyboard/gpio_keys_polled.c is used when your
+  GPIO line cannot generate interrupts, so it needs to be periodically polled
+  by a timer.
+
+- gpio_mouse: drivers/input/mouse/gpio_mouse.c is used to provide a mouse with
+  up to three buttons by simply using GPIOs and no mouse port. You can cut the
+  mouse cable and connect the wires to GPIO lines or solder a mouse connector
+  to the lines for a more permanent solution of this type.
+
+- gpio-beeper: drivers/input/misc/gpio-beeper.c is used to provide a beep from
+  an external speaker connected to a GPIO line.
+
+- gpio-tilt-polled: drivers/input/misc/gpio_tilt_polled.c provides tilt
+  detection switches using GPIO, which is useful for your homebrewn pinball
+  machine if for nothing else. It can detect different tilt angles of the
+  monitored object.
+
+- extcon-gpio: drivers/extcon/extcon-gpio.c is used when you need to read an
+  external connector status, such as a headset line for an audio driver or an
+  HDMI connector. It will provide a better userspace sysfs interface than GPIO.
+
+- restart-gpio: drivers/power/gpio-restart.c is used to restart/reboot the
+  system by pulling a GPIO line and will register a restart handler so
+  userspace can issue the right system call to restart the system.
+
+- poweroff-gpio: drivers/power/gpio-poweroff.c is used to power the system down
+  by pulling a GPIO line and will register a pm_power_off() callback so that
+  userspace can issue the right system call to power down the system.
+
+- gpio-gate-clock: drivers/clk/clk-gpio-gate.c is used to control a gated clock
+  (off/on) that uses a GPIO, and integrated with the clock subsystem.
+
+- i2c-gpio: drivers/i2c/busses/i2c-gpio.c is used to drive an I2C bus
+  (two wires, SDA and SCL lines) by hammering (bitbang) two GPIO lines. It will
+  appear as any other I2C bus to the system and makes it possible to connect
+  drivers for the I2C devices on the bus like any other I2C bus driver.
+
+- spi_gpio: drivers/spi/spi-gpio.c is used to drive an SPI bus (variable number
+  of wires, atleast SCK and optionally MISO, MOSI and chip select lines) using
+  GPIO hammering (bitbang). It will appear as any other SPI bus on the system
+  and makes it possible to connect drivers for SPI devices on the bus like
+  any other SPI bus driver. For example any MMC/SD card can then be connected
+  to this SPI by using the mmc_spi host from the MMC/SD card subsystem.
+
+- w1-gpio: drivers/w1/masters/w1-gpio.c is used to drive a one-wire bus using
+  a GPIO line, integrating with the W1 subsystem and handling devices on
+  the bus like any other W1 device.
+
+- gpio-fan: drivers/hwmon/gpio-fan.c is used to control a fan for cooling the
+  system, connected to a GPIO line (and optionally a GPIO alarm line),
+  presenting all the right in-kernel and sysfs interfaces to make your system
+  not overheat.
+
+- gpio-regulator: drivers/regulator/gpio-regulator.c is used to control a
+  regulator providing a certain voltage by pulling a GPIO line, integrating
+  with the regulator subsystem and giving you all the right interfaces.
+
+- gpio-wdt: drivers/watchdog/gpio_wdt.c is used to provide a watchdog timer
+  that will periodically "ping" a hardware connected to a GPIO line by toggling
+  it from 1-to-0-to-1. If that hardware does not recieve its "ping"
+  periodically, it will reset the system.
+
+- gpio-nand: drivers/mtd/nand/gpio.c is used to connect a NAND flash chip to
+  a set of simple GPIO lines: RDY, NCE, ALE, CLE, NWP. It interacts with the
+  NAND flash MTD subsystem and provides chip access and partition parsing like
+  any other NAND driving hardware.
+
+Apart from this there are special GPIO drivers in subsystems like MMC/SD to
+read card detect and write protect GPIO lines, and in the TTY serial subsystem
+to emulate MCTRL (modem control) signals CTS/RTS by using two GPIO lines. The
+MTD NOR flash has add-ons for extra GPIO lines too, though the address bus is
+usually connected directly to the flash.
+
+Use those instead of talking directly to the GPIOs using sysfs; they integrate
+with kernel frameworks better than your userspace code could. Needless to say,
+just using the apropriate kernel drivers will simplify and speed up your
+embedded hacking in particular by providing ready-made components.