cmd: gpio: Make `gpio input` return pin value again

4dbc107f4683 ("cmd: gpio: Correct do_gpio() return value") correctly
changed the behaviour of the gpio command to return CMD_RET_SUCCESS or
CMD_RET_FAILURE, but any existing script which expects the return value
to be the pin value is broken by this change.

Reinstate the legacy behaviour for `gpio input` only.

Fixes: 4dbc107f4683 ("cmd: gpio: Correct do_gpio() return value")
Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Signed-off-by: Alex Kiernan <alex.kiernan@hivehome.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/test/py/tests/test_gpio.py b/test/py/tests/test_gpio.py
new file mode 100644
index 0000000..8c64f68
--- /dev/null
+++ b/test/py/tests/test_gpio.py
@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: GPL-2.0+
+
+import pytest
+
+@pytest.mark.boardspec('sandbox')
+@pytest.mark.buildconfigspec('cmd_gpio')
+def test_gpio_input(u_boot_console):
+    """Test that gpio input correctly returns the value of a gpio pin."""
+
+    response = u_boot_console.run_command('gpio input 0; echo rc:$?')
+    expected_response = 'rc:0'
+    assert(expected_response in response)
+    response = u_boot_console.run_command('gpio toggle 0; gpio input 0; echo rc:$?')
+    expected_response = 'rc:1'
+    assert(expected_response in response)
+
+@pytest.mark.boardspec('sandbox')
+@pytest.mark.buildconfigspec('cmd_gpio')
+def test_gpio_exit_statuses(u_boot_console):
+    """Test that non-input gpio commands correctly return the command
+    success/failure status."""
+
+    expected_response = 'rc:0'
+    response = u_boot_console.run_command('gpio clear 0; echo rc:$?')
+    assert(expected_response in response)
+    response = u_boot_console.run_command('gpio set 0; echo rc:$?')
+    assert(expected_response in response)
+    response = u_boot_console.run_command('gpio toggle 0; echo rc:$?')
+    assert(expected_response in response)
+    response = u_boot_console.run_command('gpio status -a; echo rc:$?')
+    assert(expected_response in response)
+
+    expected_response = 'rc:1'
+    response = u_boot_console.run_command('gpio nonexistent-command; echo rc:$?')
+    assert(expected_response in response)
+    response = u_boot_console.run_command('gpio input 200; echo rc:$?')
+    assert(expected_response in response)