Re: [PATCH] hog: Destroy uHID device when disconnected

[Juha Kuikka <juha.kuikka@xxxxxxxxxxx>]

Hi Petry,

On Mon, Feb 27, 2017 at 6:17 PM, Petri Gynther <pgynther@xxxxxxxxxx> wrote:
> Hi Juha,
>
> On Mon, Feb 27, 2017 at 2:40 PM, Juha Kuikka <juha.kuikka@xxxxxxxxxxx> wrote:
>>
>> Unlink bluetooth classic HID, HoG persists the uHID device after across
>> connections. This is fine for stateless devices but some device utilize hidraw
>> to configure them upon connection and with the persisting uHID device,
>> reconnections are hidden from them.
>>
>> Similarly, applications such as game emulators may be using the presence of the
>> HID or the accompanying input event devices to indicate that it is available,
>> thus changing behavior.
>>
>> This patch destroys the uHID device upon disconnection, it gets re-created upon
>> reconnection, just like on initial connection.
>
> For HID and HoG remote controls, the reconnect latency is important
> for user experience. Thus, it is desirable that the uHID device is
> persistent across reconnects until next reboot.

I see. That makes sense, this way the whole pipeline is guaranteed to
be already open when the connection forms, leading to less dropped
button presses I suppose.

> How about adding a new config item to profiles/input/input.conf to
> control this (default = persistent uHID devices)?

Works for me. Something like this maybe? Excuse the quick patch, I
will send a revision to the set.

diff --git a/profiles/input/hog-lib.c b/profiles/input/hog-lib.c
index f41055b..2b954b3 100644
--- a/profiles/input/hog-lib.c
+++ b/profiles/input/hog-lib.c
@@ -129,6 +129,13 @@ struct gatt_request {
        void *user_data;
 };

+static bool persist_uhid = true;
+
+void bt_hog_set_persist_uhid(bool state)
+{
+       persist_uhid = state;
+}
+
 static struct gatt_request *create_request(struct bt_hog *hog,
                                                        void *user_data)
 {
diff --git a/profiles/input/hog-lib.h b/profiles/input/hog-lib.h
index 415dc63..7e81547 100644
--- a/profiles/input/hog-lib.h
+++ b/profiles/input/hog-lib.h
@@ -39,3 +39,4 @@ void bt_hog_detach(struct bt_hog *hog);

 int bt_hog_set_control_point(struct bt_hog *hog, bool suspend);
 int bt_hog_send_report(struct bt_hog *hog, void *data, size_t size, int type);
+void bt_hog_set_persist_uhid(bool state);
diff --git a/profiles/input/manager.c b/profiles/input/manager.c
index 1d31b06..129b7b5 100644
--- a/profiles/input/manager.c
+++ b/profiles/input/manager.c
@@ -43,6 +43,8 @@
 #include "device.h"
 #include "server.h"

+#include "profiles/input/hog-lib.h"
+
 static int hid_server_probe(struct btd_profile *p, struct btd_adapter *adapter)
 {
        return server_start(btd_adapter_get_address(adapter));
@@ -96,7 +98,7 @@ static int input_init(void)
        config = load_config_file(CONFIGDIR "/input.conf");
        if (config) {
                int idle_timeout;
-               gboolean uhid_enabled;
+               gboolean uhid_enabled, persist_uhid;

                idle_timeout = g_key_file_get_integer(config, "General",
                                                        "IdleTimeout", &err);
@@ -114,6 +116,15 @@ static int input_init(void)
                        input_enable_userspace_hid(uhid_enabled);
                } else
                        g_clear_error(&err);
+
+               persist_uhid = g_key_file_get_boolean(config, "General",
+                                                       "PersistUHID", &err);
+               if (!err) {
+                       DBG("input.conf: PersistUHID=%s", persist_uhid ?
+                                                       "true" : "false");
+                       bt_hog_set_persist_uhid(persist_uhid);
+               } else
+                       g_clear_error(&err);
        }

        btd_profile_register(&input_profile);

Thanks,
 - Juha
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