Record GPIO location in handle

lib/gpio.ex

@@ -237,12 +237,15 @@ defmodule Circuits.GPIO do
   end
 
   @doc """
-  Return dynamic configuration and status information about a GPIO
+  Return dynamic configuration and status information about a GPIO or handle
 
-  See `t:gpio_spec/0` for the ways of referring to GPIOs. If the GPIO is found,
-  this function returns information about the GPIO.
+  Pass a `t:gpio_spec/0` to query a GPIO without opening it, or a `t:Handle.t/0`
+  to query an open GPIO. If the GPIO is found, this function returns information
+  about the GPIO. Status for GPIO groups is not supported.
   """
-  @spec status(gpio_spec()) :: {:ok, status()} | {:error, atom()}
+  @spec status(gpio_spec() | Handle.t()) :: {:ok, status()} | {:error, atom()}
+  def status(handle) when is_struct(handle), do: Handle.status(handle)
+
   def status(gpio_spec) do
     {backend, backend_defaults} = default_backend()
 

lib/gpio/cdev.ex

@@ -28,7 +28,7 @@ defmodule Circuits.GPIO.CDev do
   alias Circuits.GPIO.Handle
   alias Circuits.GPIO.Nif
 
-  defstruct [:ref]
+  defstruct [:ref, :locations]
 
   @impl Backend
   def enumerate(options) do
@@ -128,7 +128,8 @@ defmodule Circuits.GPIO.CDev do
     with {:ok, controller, offsets} <- resolve_group(specs, options),
          {:ok, ref} <-
            Nif.open(gpio_spec, {controller, offsets}, direction, value, pull_mode, drive_mode) do
-      {:ok, %__MODULE__{ref: ref}}
+      locations = Enum.map(offsets, &{controller, &1})
+      {:ok, %__MODULE__{ref: ref, locations: locations}}
     end
   end
 
@@ -173,6 +174,15 @@ defmodule Circuits.GPIO.CDev do
       Nif.read(ref)
     end
 
+    @impl Handle
+    def status(%Circuits.GPIO.CDev{locations: [location]}) do
+      Nif.status(location)
+    end
+
+    def status(%Circuits.GPIO.CDev{}) do
+      {:error, :group_handle}
+    end
+
     @impl Handle
     def write(%Circuits.GPIO.CDev{ref: ref}, value) do
       Nif.write(ref, value)

lib/gpio/handle.ex

@@ -16,6 +16,11 @@ defprotocol Circuits.GPIO.Handle do
   @spec read(t()) :: GPIO.value()
   def read(handle)
 
+  # Return dynamic GPIO configuration and status information.
+  @doc false
+  @spec status(t()) :: {:ok, GPIO.status()} | {:error, atom()}
+  def status(handle)
+
   # Set the GPIO state. For a group, this is an integer with one bit per line.
   @doc false
   @spec write(t(), GPIO.value()) :: :ok

test/circuits_gpio_test.exs

@@ -166,7 +166,7 @@ defmodule Circuits.GPIOTest do
     end
   end
 
-  describe "status/2" do
+  describe "status/1" do
     test "all gpio_spec examples" do
       expected = %{consumer: "", direction: :input, pull_mode: :none, drive_mode: :push_pull}
 
@@ -215,6 +215,29 @@ defmodule Circuits.GPIOTest do
 
       GPIO.close(gpio)
     end
+
+    test "status reports an open GPIO handle" do
+      {:ok, gpio} = GPIO.open({@gpiochip, 1}, :input, pull_mode: :pullup)
+
+      assert GPIO.status(gpio) ==
+               {:ok,
+                %{
+                  consumer: "stub",
+                  direction: :input,
+                  pull_mode: :pullup,
+                  drive_mode: :push_pull
+                }}
+
+      GPIO.close(gpio)
+    end
+
+    test "status does not support GPIO groups" do
+      {:ok, gpio} = GPIO.open([{@gpiochip, 0}, {@gpiochip, 1}], :input)
+
+      assert GPIO.status(gpio) == {:error, :group_handle}
+
+      GPIO.close(gpio)
+    end
   end
 
   describe "drive_mode" do