Re: [PATCH libgpiod v5 4/4] dbus: add the D-Bus daemon, command-line client and tests

["Sverdlin, Alexander" <alexander.sverdlin@xxxxxxxxxxx>]

Hi Bartosz!

On Mon, 2024-08-12 at 10:22 +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> 
> Add the D-Bus API definition and its implementation in the form of a GPIO
> manager daemon and a companion command-line client as well as some
> additional configuration and data files (systemd service, example udev
> configuration, etc.) and test suites.
> 
> Tested-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxxxx>
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>

[]

> diff --git a/dbus/client/wait.c b/dbus/client/wait.c
> new file mode 100644
> index 0000000..d65c4e7
> --- /dev/null
> +++ b/dbus/client/wait.c
> @@ -0,0 +1,188 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +// SPDX-FileCopyrightText: 2023 Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> +
> +#include <stdlib.h>
> +
> +#include "common.h"
> +
> +typedef struct {
> +	gboolean name_done;
> +	gboolean chip_done;
> +	const gchar *label;
> +} WaitData;
> +
> +static void obj_match_label(GpiodbusObject *chip_obj, WaitData *data)
> +{
> +	GpiodbusChip *chip = gpiodbus_object_peek_chip(chip_obj);
> +
> +	if (g_strcmp0(gpiodbus_chip_get_label(chip), data->label) == 0)
> +		data->chip_done = TRUE;
> +}
> +
> +static void check_label(gpointer elem, gpointer user_data)
> +{
> +	WaitData *data = user_data;
> +	GpiodbusObject *obj = elem;
> +
> +	obj_match_label(obj, data);
> +}
> +
> +static void on_object_added(GDBusObjectManager *manager G_GNUC_UNUSED,
> +			    GpiodbusObject *obj, gpointer user_data)
> +{
> +	WaitData *data = user_data;
> +
> +	obj_match_label(GPIODBUS_OBJECT(obj), data);
> +}
> +
> +static void wait_for_chip(WaitData *data)
> +{
> +	g_autoptr(GDBusObjectManager) manager = NULL;
> +	g_autolist(GpiodbusObject) objs = NULL;
> +
> +	manager = get_object_manager_client("/io/gpiod1/chips");
> +
> +	g_signal_connect(manager, "object-added",
> +			 G_CALLBACK(on_object_added), data);
> +
> +	objs = g_dbus_object_manager_get_objects(manager);
> +	g_list_foreach(objs, check_label, data);

Strange, I'd expect from this code to detect pre-existing chips immediately,
but this is not what I observe in practice:

$ gpiocli info --chip=gpiochip0 | head -n 1
gpiochip0 - 24 lines:
$ gpiocli wait --chip=gpiochip0 --timeout=1
gpiocli wait: wait timed out!

(without timeout it would wait endlessly)

This is not expected, right, otherwise it would be counter-intuitive and racy?

-- 
Alexander Sverdlin
Siemens AG
www.siemens.com