Hi Luiz,
On Fri, Feb 28, 2025 at 5:40 AM Luiz Augusto von Dentz
<luiz.dentz@xxxxxxxxx> wrote:
>
> Hi Hsin-chen,
>
> On Thu, Feb 27, 2025 at 12:14 PM Hsin-chen Chuang <chharry@xxxxxxxxxx> wrote:
> >
> > From: Hsin-chen Chuang <chharry@xxxxxxxxxxxx>
> >
> > Automatically configure the altsetting for HCI_USER_CHANNEL when a SCO
> > is connected.
> >
> > The motivation is to enable the HCI_USER_CHANNEL user to send out SCO
> > data through USB Bluetooth chips, which is mainly used for bidirectional
> > audio transfer (voice call). This was not capable because:
> >
> > - Per Bluetooth Core Spec v5, Vol 4, Part B, 2.1, the corresponding
> > alternate setting should be set based on the air mode in order to
> > transfer SCO data, but
> > - The Linux Bluetooth HCI_USER_CHANNEL exposes the Bluetooth Host
> > Controller Interface to the user space, which is something above the
> > USB layer. The user space is not able to configure the USB alt while
> > keeping the channel open.
> >
> > This patch intercepts the HCI_EV_SYNC_CONN_COMPLETE packets in btusb,
> > extracts the air mode, and configures the alt setting in btusb.
> >
> > This patch is tested on ChromeOS devices. The USB Bluetooth models
> > (CVSD, TRANS alt3 and alt6) could work without a customized kernel.
> >
> > Fixes: b16b327edb4d ("Bluetooth: btusb: add sysfs attribute to control USB alt setting")
> > Signed-off-by: Hsin-chen Chuang <chharry@xxxxxxxxxxxx>
> > ---
> >
> > Changes in v3:
> > - Remove module parameter
> > - Set Kconfig to default y if CHROME_PLATFORMS
> >
> > Changes in v2:
> > - Give up tracking the SCO handles. Only configure the altsetting when
> > SCO connected.
> > - Put the change behind Kconfig/module parameter
> >
> > drivers/bluetooth/Kconfig | 11 ++++++++++
> > drivers/bluetooth/btusb.c | 43 +++++++++++++++++++++++++++++++++++++++
> > 2 files changed, 54 insertions(+)
> >
> > diff --git a/drivers/bluetooth/Kconfig b/drivers/bluetooth/Kconfig
> > index 4ab32abf0f48..cdf7a5caa5c8 100644
> > --- a/drivers/bluetooth/Kconfig
> > +++ b/drivers/bluetooth/Kconfig
> > @@ -56,6 +56,17 @@ config BT_HCIBTUSB_POLL_SYNC
> > Say Y here to enable USB poll_sync for Bluetooth USB devices by
> > default.
> >
> > +config BT_HCIBTUSB_AUTO_SET_ISOC_ALT
> > + bool "Auto set isoc_altsetting for HCI_USER_CHANNEL when SCO connected"
> > + depends on BT_HCIBTUSB
> > + default y if CHROME_PLATFORMS
> > + help
> > + Say Y here to enable auto set isoc_altsetting for HCI_USER_CHANNEL
> > + when SCO connected
> > +
> > + When enabled, btusb intercepts the HCI_EV_SYNC_CONN_COMPLETE packets
> > + and configures isoc_altsetting automatically for HCI_USER_CHANNEL.
> > +
> > config BT_HCIBTUSB_BCM
> > bool "Broadcom protocol support"
> > depends on BT_HCIBTUSB
> > diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
> > index de3fa725d210..2642d2ca885f 100644
> > --- a/drivers/bluetooth/btusb.c
> > +++ b/drivers/bluetooth/btusb.c
> > @@ -34,6 +34,8 @@ static bool force_scofix;
> > static bool enable_autosuspend = IS_ENABLED(CONFIG_BT_HCIBTUSB_AUTOSUSPEND);
> > static bool enable_poll_sync = IS_ENABLED(CONFIG_BT_HCIBTUSB_POLL_SYNC);
> > static bool reset = true;
> > +static bool auto_set_isoc_alt =
> > + IS_ENABLED(CONFIG_BT_HCIBTUSB_AUTO_SET_ISOC_ALT);
> >
> > static struct usb_driver btusb_driver;
> >
> > @@ -1113,6 +1115,42 @@ static inline void btusb_free_frags(struct btusb_data *data)
> > spin_unlock_irqrestore(&data->rxlock, flags);
> > }
> >
> > +static void btusb_sco_connected(struct btusb_data *data, struct sk_buff *skb)
> > +{
> > + struct hci_event_hdr *hdr = (void *) skb->data;
> > + struct hci_ev_sync_conn_complete *ev =
> > + (void *) skb->data + sizeof(*hdr);
> > + struct hci_dev *hdev = data->hdev;
> > + unsigned int notify_air_mode;
> > +
> > + if (hci_skb_pkt_type(skb) != HCI_EVENT_PKT)
> > + return;
> > +
> > + if (skb->len < sizeof(*hdr) || hdr->evt != HCI_EV_SYNC_CONN_COMPLETE)
> > + return;
> > +
> > + if (skb->len != sizeof(*hdr) + sizeof(*ev) || ev->status)
> > + return;
> > +
> > + switch (ev->air_mode) {
> > + case BT_CODEC_CVSD:
> > + notify_air_mode = HCI_NOTIFY_ENABLE_SCO_CVSD;
> > + break;
> > +
> > + case BT_CODEC_TRANSPARENT:
> > + notify_air_mode = HCI_NOTIFY_ENABLE_SCO_TRANSP;
> > + break;
> > +
> > + default:
> > + return;
> > + }
> > +
> > + bt_dev_info(hdev, "enabling SCO with air mode %u", ev->air_mode);
> > + data->sco_num = 1;
> > + data->air_mode = notify_air_mode;
> > + schedule_work(&data->work);
> > +}
> > +
> > static int btusb_recv_event(struct btusb_data *data, struct sk_buff *skb)
> > {
> > if (data->intr_interval) {
> > @@ -1120,6 +1158,11 @@ static int btusb_recv_event(struct btusb_data *data, struct sk_buff *skb)
> > schedule_delayed_work(&data->rx_work, 0);
> > }
> >
> > + /* Configure altsetting for HCI_USER_CHANNEL on SCO connected */
> > + if (auto_set_isoc_alt &&
> > + hci_dev_test_flag(data->hdev, HCI_USER_CHANNEL))
> > + btusb_sco_connected(data, skb);
> > +
> > return data->recv_event(data->hdev, skb);
> > }
> >
> > --
> > 2.48.1.658.g4767266eb4-goog
>
> This has been merged, I did some minor rewording here and there but
> the logic remains the same, now we can problem revert b16b327edb4d
> ("Bluetooth: btusb: add sysfs attribute to control USB alt setting")?
>
> --
> Luiz Augusto von Dentz
Yes, sure. We could revert b16b327edb4d now.
Best Regards,
Hsin-chen
