cmd: gpio: Make gpio input return pin value again

4dbc107f46 ("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: 4dbc107f46 ("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>

cmd/gpio.c

@@ -248,7 +248,12 @@ static int do_gpio(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 	if (ret != -EBUSY)
 		gpio_free(gpio);
 
-	return CMD_RET_SUCCESS;
+	/*
+	 * Whilst wrong, the legacy gpio input command returns the pin
+	 * value, or CMD_RET_FAILURE (which is indistinguishable from a
+	 * valid pin value).
+	 */
+	return (sub_cmd == GPIOC_INPUT) ? value : CMD_RET_SUCCESS;
 
 err:
 	if (ret != -EBUSY)

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)