Re: [PATCH v2 3/3] hog: Optionally destroy uHID device when disconnected

On Wed, Mar 1, 2017 at 2:58 AM, Luiz Augusto von Dentz
[off-list ref] wrote:

Hi Juha,

On Wed, Mar 1, 2017 at 3:06 AM, Juha Kuikka [off-list ref] wrote:

quoted

Unlink bluetooth classic HID, HoG persists the uHID device after across
connections. This is fine for stateless devices that require fast reconnections
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 introduces a configuration option that, when set, destroys the uHID
device upon disconnection, it gets re-created upon reconnection, just like on
initial connection.
---
 profiles/input/hog-lib.c | 29 +++++++++++++++++++++++++++++
 profiles/input/hog-lib.h |  1 +
 2 files changed, 30 insertions(+)

diff --git a/profiles/input/hog-lib.c b/profiles/input/hog-lib.c
index dab385f..b2a371e 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 uhid_destroy = false;
+
+void bt_hog_set_uhid_destroy(bool state)
+{
+       uhid_destroy = state;
+}
+
 static struct gatt_request *create_request(struct bt_hog *hog,
                                                        void *user_data)
 {

@@ -1565,6 +1572,25 @@ static void primary_cb(uint8_t status, GSList *services, void *user_data)
        }
 }

+static void destroy_uhid(struct bt_hog *hog)
+{
+       struct uhid_event ev = {
+               .type = UHID_DESTROY
+       };
+       int err;
+
+       if (hog->uhid_created) {
+               err = bt_uhid_send(hog->uhid, &ev);
+               if (err < 0) {
+                       error("bt_uhid_send: %s", strerror(-err));
+                       return;
+               }
+               hog->uhid_created = false;
+
+               DBG("HoG destroyed uHID device");
+       }
+}
+
 bool bt_hog_attach(struct bt_hog *hog, void *gatt)
 {
        GSList *l;

@@ -1651,6 +1677,9 @@ void bt_hog_detach(struct bt_hog *hog)
        queue_foreach(hog->gatt_op, (void *) cancel_gatt_req, NULL);
        g_attrib_unref(hog->attrib);
        hog->attrib = NULL;
+
+       if (uhid_destroy)
+               destroy_uhid(hog);

It probably make sense to check if hog->uhid_created.

That is checked within destroy_uhid() but I can move it here so the
checks are all in one place.

quoted

 }

 int bt_hog_set_control_point(struct bt_hog *hog, bool suspend)

diff --git a/profiles/input/hog-lib.h b/profiles/input/hog-lib.h
index 415dc63..de8c42f 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_uhid_destroy(bool state);

Ive made this per instance.

quoted

--
2.7.4

I would consider doing this in the bt_uhid instance

Can you elaborate? Moving the uhid_destroy flag into struct bt_uhid?
Or just into the src/shared/uhid.c? Since the configuration file
option is global and read before anything else, no instances of bt_hog
or bt_uhid are present. Are you thinking of adding a runtime
configuration mechanism?

The user of bt_uhid is responsible for creating the uhid device so I
made the destruction mirror that.

 - Juha