Kernel-3.10.0-957.el7_gpio-properties

published: updated: Kernel_3.10.0-957.el7_内核文档

With the release of ACPI 5.1 and the _DSD configuration objecte names
can finally be given to GPIOs (and other things as well) returned by
_CRS. Previously, we were only able to use an integer index to find
the corresponding GPIO, which is pretty error prone (it depends on
the _CRS output ordering, for example).

With _DSD we can now query GPIOs using a name instead of an integer
index, like the ASL example below shows:

// Bluetooth device with reset and shutdown GPIOs
Device (BTH)
{
Name (_HID, …)

  Name (_CRS, ResourceTemplate ()
  {
      GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly,
              "\\_SB.GPO0", 0, ResourceConsumer) {15}
      GpioIo (Exclusive, PullUp, 0, 0, IoRestrictionInputOnly,
              "\\_SB.GPO0", 0, ResourceConsumer) {27, 31}
  })

  Name (_DSD, Package ()
  {
      ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
      Package ()
  {
          Package () {"reset-gpio", Package() {^BTH, 1, 1, 0 }},
          Package () {"shutdown-gpio", Package() {^BTH, 0, 0, 0 }},
      }
  })

}

The format of the supported GPIO property is:

Package () { “name”, Package () { ref, index, pin, active_low }}

ref - The device that has _CRS containing GpioIo()/GpioInt() resources,
typically this is the device itself (BTH in our case).
index - Index of the GpioIo()/GpioInt() resource in _CRS starting from zero.
pin - Pin in the GpioIo()/GpioInt() resource. Typically this is zero.
active_low - If 1 the GPIO is marked as active_low.

Since ACPI GpioIo() resource does not have a field saying whether it is
active low or high, the “active_low” argument can be used here. Setting
it to 1 marks the GPIO as active low.

In our Bluetooth example the “reset-gpio” refers to the second GpioIo()
resource, second pin in that resource with the GPIO number of 31.

oosTech by Sam Lee