It is desirable to define the HCI packet payload sizes of
USB alternate settings so that they can be exposed to user
space.
Reviewed-by: Alain Michaud <[email protected]>
Reviewed-by: Abhishek Pandit-Subedi <[email protected]>
Signed-off-by: Joseph Hwang <[email protected]>
---
Changes in v3:
- Set hdev->sco_mtu to rp->sco_mtu if the latter is smaller.
Changes in v2:
- Used sco_mtu instead of a new sco_pkt_len member in hdev.
- Do not overwrite hdev->sco_mtu in hci_cc_read_buffer_size
if it has been set in the USB interface.
drivers/bluetooth/btusb.c | 45 +++++++++++++++++++++++++++++----------
net/bluetooth/hci_event.c | 14 +++++++++++-
2 files changed, 47 insertions(+), 12 deletions(-)
diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index fe80588c7bd3a8..651d5731a6c6cf 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -459,6 +459,24 @@ static const struct dmi_system_id btusb_needs_reset_resume_table[] = {
#define BTUSB_WAKEUP_DISABLE 14
#define BTUSB_USE_ALT1_FOR_WBS 15
+/* Per core spec 5, vol 4, part B, table 2.1,
+ * list the hci packet payload sizes for various ALT settings.
+ * This is used to set the packet length for the wideband speech.
+ * If a controller does not probe its usb alt setting, the default
+ * value will be 0. Any clients at upper layers should interpret it
+ * as a default value and set a proper packet length accordingly.
+ *
+ * To calculate the HCI packet payload length:
+ * for alternate settings 1 - 5:
+ * hci_packet_size = suggested_max_packet_size * 3 (packets) -
+ * 3 (HCI header octets)
+ * for alternate setting 6:
+ * hci_packet_size = suggested_max_packet_size - 3 (HCI header octets)
+ * where suggested_max_packet_size is {9, 17, 25, 33, 49, 63}
+ * for alt settings 1 - 6.
+ */
+static const int hci_packet_size_usb_alt[] = { 0, 24, 48, 72, 96, 144, 60 };
+
struct btusb_data {
struct hci_dev *hdev;
struct usb_device *udev;
@@ -3959,6 +3977,15 @@ static int btusb_probe(struct usb_interface *intf,
hdev->notify = btusb_notify;
hdev->prevent_wake = btusb_prevent_wake;
+ if (id->driver_info & BTUSB_AMP) {
+ /* AMP controllers do not support SCO packets */
+ data->isoc = NULL;
+ } else {
+ /* Interface orders are hardcoded in the specification */
+ data->isoc = usb_ifnum_to_if(data->udev, ifnum_base + 1);
+ data->isoc_ifnum = ifnum_base + 1;
+ }
+
#ifdef CONFIG_PM
err = btusb_config_oob_wake(hdev);
if (err)
@@ -4022,6 +4049,10 @@ static int btusb_probe(struct usb_interface *intf,
hdev->set_diag = btintel_set_diag;
hdev->set_bdaddr = btintel_set_bdaddr;
hdev->cmd_timeout = btusb_intel_cmd_timeout;
+
+ if (btusb_find_altsetting(data, 6))
+ hdev->sco_mtu = hci_packet_size_usb_alt[6];
+
set_bit(HCI_QUIRK_STRICT_DUPLICATE_FILTER, &hdev->quirks);
set_bit(HCI_QUIRK_SIMULTANEOUS_DISCOVERY, &hdev->quirks);
set_bit(HCI_QUIRK_NON_PERSISTENT_DIAG, &hdev->quirks);
@@ -4063,15 +4094,6 @@ static int btusb_probe(struct usb_interface *intf,
btusb_check_needs_reset_resume(intf);
}
- if (id->driver_info & BTUSB_AMP) {
- /* AMP controllers do not support SCO packets */
- data->isoc = NULL;
- } else {
- /* Interface orders are hardcoded in the specification */
- data->isoc = usb_ifnum_to_if(data->udev, ifnum_base + 1);
- data->isoc_ifnum = ifnum_base + 1;
- }
-
if (IS_ENABLED(CONFIG_BT_HCIBTUSB_RTL) &&
(id->driver_info & BTUSB_REALTEK)) {
hdev->setup = btrtl_setup_realtek;
@@ -4083,9 +4105,10 @@ static int btusb_probe(struct usb_interface *intf,
* (DEVICE_REMOTE_WAKEUP)
*/
set_bit(BTUSB_WAKEUP_DISABLE, &data->flags);
- if (btusb_find_altsetting(data, 1))
+ if (btusb_find_altsetting(data, 1)) {
set_bit(BTUSB_USE_ALT1_FOR_WBS, &data->flags);
- else
+ hdev->sco_mtu = hci_packet_size_usb_alt[1];
+ } else
bt_dev_err(hdev, "Device does not support ALT setting 1");
}
diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
index 33d8458fdd4adc..1869dc7ebbb5ac 100644
--- a/net/bluetooth/hci_event.c
+++ b/net/bluetooth/hci_event.c
@@ -730,7 +730,19 @@ static void hci_cc_read_buffer_size(struct hci_dev *hdev, struct sk_buff *skb)
return;
hdev->acl_mtu = __le16_to_cpu(rp->acl_mtu);
- hdev->sco_mtu = rp->sco_mtu;
+ /* If the host controller interface is USB, the hdev->sco_mtu is
+ * set in btusb.c and is not expected to be larger than the max sco
+ * buffer size returned from the controller in rp->sco_mtu.
+ */
+ if (hdev->sco_mtu > 0) {
+ if (rp->sco_mtu < hdev->sco_mtu) {
+ BT_ERR("sco mtu %d changed to max sco buffer size %d",
+ hdev->sco_mtu, rp->sco_mtu);
+ hdev->sco_mtu = rp->sco_mtu;
+ }
+ } else {
+ hdev->sco_mtu = rp->sco_mtu;
+ }
hdev->acl_pkts = __le16_to_cpu(rp->acl_max_pkt);
hdev->sco_pkts = __le16_to_cpu(rp->sco_max_pkt);
--
2.28.0.618.gf4bc123cb7-goog
On Thursday 10 September 2020 14:04:01 Joseph Hwang wrote:
> It is desirable to define the HCI packet payload sizes of
> USB alternate settings so that they can be exposed to user
> space.
>
> Reviewed-by: Alain Michaud <[email protected]>
> Reviewed-by: Abhishek Pandit-Subedi <[email protected]>
> Signed-off-by: Joseph Hwang <[email protected]>
> ---
>
> Changes in v3:
> - Set hdev->sco_mtu to rp->sco_mtu if the latter is smaller.
>
> Changes in v2:
> - Used sco_mtu instead of a new sco_pkt_len member in hdev.
> - Do not overwrite hdev->sco_mtu in hci_cc_read_buffer_size
> if it has been set in the USB interface.
>
> drivers/bluetooth/btusb.c | 45 +++++++++++++++++++++++++++++----------
> net/bluetooth/hci_event.c | 14 +++++++++++-
> 2 files changed, 47 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
> index fe80588c7bd3a8..651d5731a6c6cf 100644
> --- a/drivers/bluetooth/btusb.c
> +++ b/drivers/bluetooth/btusb.c
> @@ -459,6 +459,24 @@ static const struct dmi_system_id btusb_needs_reset_resume_table[] = {
> #define BTUSB_WAKEUP_DISABLE 14
> #define BTUSB_USE_ALT1_FOR_WBS 15
>
> +/* Per core spec 5, vol 4, part B, table 2.1,
> + * list the hci packet payload sizes for various ALT settings.
> + * This is used to set the packet length for the wideband speech.
> + * If a controller does not probe its usb alt setting, the default
> + * value will be 0. Any clients at upper layers should interpret it
> + * as a default value and set a proper packet length accordingly.
> + *
> + * To calculate the HCI packet payload length:
> + * for alternate settings 1 - 5:
> + * hci_packet_size = suggested_max_packet_size * 3 (packets) -
> + * 3 (HCI header octets)
> + * for alternate setting 6:
> + * hci_packet_size = suggested_max_packet_size - 3 (HCI header octets)
> + * where suggested_max_packet_size is {9, 17, 25, 33, 49, 63}
> + * for alt settings 1 - 6.
Thank you for update, now I see what you mean!
> + */
> +static const int hci_packet_size_usb_alt[] = { 0, 24, 48, 72, 96, 144, 60 };
Now the another question, why you are using hci_packet_size_usb_alt[1]
and hci_packet_size_usb_alt[6] values from this array?
> +
> struct btusb_data {
> struct hci_dev *hdev;
> struct usb_device *udev;
> @@ -3959,6 +3977,15 @@ static int btusb_probe(struct usb_interface *intf,
> hdev->notify = btusb_notify;
> hdev->prevent_wake = btusb_prevent_wake;
>
> + if (id->driver_info & BTUSB_AMP) {
> + /* AMP controllers do not support SCO packets */
> + data->isoc = NULL;
> + } else {
> + /* Interface orders are hardcoded in the specification */
> + data->isoc = usb_ifnum_to_if(data->udev, ifnum_base + 1);
> + data->isoc_ifnum = ifnum_base + 1;
> + }
> +
> #ifdef CONFIG_PM
> err = btusb_config_oob_wake(hdev);
> if (err)
> @@ -4022,6 +4049,10 @@ static int btusb_probe(struct usb_interface *intf,
> hdev->set_diag = btintel_set_diag;
> hdev->set_bdaddr = btintel_set_bdaddr;
> hdev->cmd_timeout = btusb_intel_cmd_timeout;
> +
> + if (btusb_find_altsetting(data, 6))
> + hdev->sco_mtu = hci_packet_size_usb_alt[6];
Why you are setting this sco_mtu only for Intel adapter? Is not this
whole code generic to USB?
> +
> set_bit(HCI_QUIRK_STRICT_DUPLICATE_FILTER, &hdev->quirks);
> set_bit(HCI_QUIRK_SIMULTANEOUS_DISCOVERY, &hdev->quirks);
> set_bit(HCI_QUIRK_NON_PERSISTENT_DIAG, &hdev->quirks);
> @@ -4063,15 +4094,6 @@ static int btusb_probe(struct usb_interface *intf,
> btusb_check_needs_reset_resume(intf);
> }
>
> - if (id->driver_info & BTUSB_AMP) {
> - /* AMP controllers do not support SCO packets */
> - data->isoc = NULL;
> - } else {
> - /* Interface orders are hardcoded in the specification */
> - data->isoc = usb_ifnum_to_if(data->udev, ifnum_base + 1);
> - data->isoc_ifnum = ifnum_base + 1;
> - }
> -
> if (IS_ENABLED(CONFIG_BT_HCIBTUSB_RTL) &&
> (id->driver_info & BTUSB_REALTEK)) {
> hdev->setup = btrtl_setup_realtek;
> @@ -4083,9 +4105,10 @@ static int btusb_probe(struct usb_interface *intf,
> * (DEVICE_REMOTE_WAKEUP)
> */
> set_bit(BTUSB_WAKEUP_DISABLE, &data->flags);
> - if (btusb_find_altsetting(data, 1))
> + if (btusb_find_altsetting(data, 1)) {
> set_bit(BTUSB_USE_ALT1_FOR_WBS, &data->flags);
> - else
> + hdev->sco_mtu = hci_packet_size_usb_alt[1];
And this part of code which you write is Realtek specific.
I thought that this is something generic to bluetooth usb as you pointed
to bluetooth documentation "core spec 5, vol 4, part B, table 2.1".
> + } else
> bt_dev_err(hdev, "Device does not support ALT setting 1");
> }
Also this patch seems to be for me incomplete or not fully correct as
USB altsetting is chosen in function btusb_work() and it depends on
selected AIR mode (which is configured by another setsockopt).
So despite what is written in commit message, this patch looks for me
like some hack for Intel and Realtek bluetooth adapters and does not
solve problems in vendor independent manner.
On Wednesday, September 23, 2020 3:22:15 AM PST Pali Rohár wrote:
> On Monday 14 September 2020 20:18:27 Joseph Hwang wrote:
> > On Thu, Sep 10, 2020 at 4:18 PM Pali Rohár <[email protected]> wrote:
> > > And this part of code which you write is Realtek specific.
> >
> > We currently only have Intel and Realtek platforms to test with. If
> > making it generic without proper testing platforms is fine, I will
> > make it generic. Or do you think it might be better to make it
> > customized with particular vendors for now; and make it generic later
> > when it works well with sufficient vendors?
>
> I understood that those packet size changes are generic to bluetooth
> specification and therefore it is not vendor specific code. Those packet
> sizes for me really seems to be USB specific.
>
> Therefore it should apply for all vendors, not only for Realtek and
> Intel.
I have tried to test WBS with some different USB adapters. So far, all use
these packet sizes. Tested were:
Broadcom BRCM20702A
Realtek RTL8167B
Realtek RTL8821C
CSR CSR8510 (probably fake)
In all cases, WBS works best with packet size of (USB packet size for alt mode
selected) * 3 packets - 3 bytes HCI header. None of these devices support alt
6 mode, where supposedly one packet is better, but I can find no BT adapter on
which to test this.
> +static const int hci_packet_size_usb_alt[] = { 0, 24, 48, 72, 96, 144, 60};
Note that the packet sizes here are based on the max isoc packet length for
the USB alt mode used, e.g. alt 1 is 9 bytes. That value is only a
"recommended" value from the bluetooth spec. It seems like it would be more
correct use (btusb_data*)->isoc_tx_ep->wMaxPacketSize to find the MTU.
> > [Issue 2] The btusb_work() is performed by a worker. There would be a
> > timing issue here if we let btusb_work() to do “hdev->sco_mtu =
> > hci_packet_size_usb_alt[i]” because there is no guarantee how soon the
> > btusb_work() can be finished and get “hdev->sco_mtu” value set
> > correctly. In order to avoid the potential race condition, I suggest
> > to determine air_mode in btusb_notify() before
> > schedule_work(&data->work) is executed so that “hdev->sco_mtu =
> > hci_packet_size_usb_alt[i]” is guaranteed to be performed when
> > btusb_notify() finished. In this way, hci_sync_conn_complete_evt() can
> > set conn->mtu correctly as described in [Issue 1] above.
Does this also give userspace a clear point at which to determine MTU setting,
_before_ data is sent over SCO connection? It will not work if sco_mtu is not
valid until after userspace sends data to SCO connection with incorrect mtu.
On Tuesday 08 December 2020 15:04:29 Trent Piepho wrote:
> On Wednesday, September 23, 2020 3:22:15 AM PST Pali Rohár wrote:
> > On Monday 14 September 2020 20:18:27 Joseph Hwang wrote:
> > > On Thu, Sep 10, 2020 at 4:18 PM Pali Rohár <[email protected]> wrote:
> > > > And this part of code which you write is Realtek specific.
> > >
> > > We currently only have Intel and Realtek platforms to test with. If
> > > making it generic without proper testing platforms is fine, I will
> > > make it generic. Or do you think it might be better to make it
> > > customized with particular vendors for now; and make it generic later
> > > when it works well with sufficient vendors?
> >
> > I understood that those packet size changes are generic to bluetooth
> > specification and therefore it is not vendor specific code. Those packet
> > sizes for me really seems to be USB specific.
> >
> > Therefore it should apply for all vendors, not only for Realtek and
> > Intel.
>
> I have tried to test WBS with some different USB adapters. So far, all use
> these packet sizes. Tested were:
>
> Broadcom BRCM20702A
> Realtek RTL8167B
> Realtek RTL8821C
> CSR CSR8510 (probably fake)
>
> In all cases, WBS works best with packet size of (USB packet size for alt mode
> selected) * 3 packets - 3 bytes HCI header. None of these devices support alt
> 6 mode, where supposedly one packet is better, but I can find no BT adapter on
> which to test this.
>
> > +static const int hci_packet_size_usb_alt[] = { 0, 24, 48, 72, 96, 144, 60};
>
> Note that the packet sizes here are based on the max isoc packet length for
> the USB alt mode used, e.g. alt 1 is 9 bytes. That value is only a
> "recommended" value from the bluetooth spec. It seems like it would be more
> correct use (btusb_data*)->isoc_tx_ep->wMaxPacketSize to find the MTU.
Yea, wMaxPacketSize looks like a candidate for determining MTU. Can we
use it or are there any known issues with it?
> > > [Issue 2] The btusb_work() is performed by a worker. There would be a
> > > timing issue here if we let btusb_work() to do “hdev->sco_mtu =
> > > hci_packet_size_usb_alt[i]” because there is no guarantee how soon the
> > > btusb_work() can be finished and get “hdev->sco_mtu” value set
> > > correctly. In order to avoid the potential race condition, I suggest
> > > to determine air_mode in btusb_notify() before
> > > schedule_work(&data->work) is executed so that “hdev->sco_mtu =
> > > hci_packet_size_usb_alt[i]” is guaranteed to be performed when
> > > btusb_notify() finished. In this way, hci_sync_conn_complete_evt() can
> > > set conn->mtu correctly as described in [Issue 1] above.
>
> Does this also give userspace a clear point at which to determine MTU setting,
> _before_ data is sent over SCO connection? It will not work if sco_mtu is not
> valid until after userspace sends data to SCO connection with incorrect mtu.
IIRC connection is established after sync connection (SCO) complete
event. And sending data is possible after connection is established. So
based on these facts I think that userspace can determinate MTU settings
prior sending data over SCO socket.
Anyway, to whole MTU issue for SCO there is a nice workaround which
worked fine with more tested USB adapters and headsets. As SCO socket is
synchronous and most bluetooth headsets have own clocks, you can
synchronize sending packets to headsets based on time events when you
received packets from other side and also send packets of same size as
you received. I.e. for every received packet send own packet of the same
size.