[v2,4/4] Bluetooth: Queue a HCI power-off command before rfkilling adapters

  On a lot of platforms (at least the MS Surface devices, M1 macbooks, and
a few ThinkPads) firmware doesn't do its job when rfkilling a device
and the bluetooth adapter is not actually shut down on rfkill. This leads
to connected devices remaining in connected state and the bluetooth
connection eventually timing out after rfkilling an adapter.

Use the rfkill hook in the HCI driver to actually power the device off
before rfkilling it.

Note that the wifi subsystem is doing something similar by calling
cfg80211_shutdown_all_interfaces()
in it's rfkill set_block callback (see cfg80211_rfkill_set_block).

Signed-off-by: Jonas Dreßler <verdre@v0yd.nl>
---
 net/bluetooth/hci_core.c | 33 ++++++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)
  

Hi Jonas,

On Tue, Jan 2, 2024 at 1:19 PM Jonas Dreßler <verdre@v0yd.nl> wrote:
>
> On a lot of platforms (at least the MS Surface devices, M1 macbooks, and
> a few ThinkPads) firmware doesn't do its job when rfkilling a device
> and the bluetooth adapter is not actually shut down on rfkill. This leads
> to connected devices remaining in connected state and the bluetooth
> connection eventually timing out after rfkilling an adapter.
>
> Use the rfkill hook in the HCI driver to actually power the device off
> before rfkilling it.
>
> Note that the wifi subsystem is doing something similar by calling
> cfg80211_shutdown_all_interfaces()
> in it's rfkill set_block callback (see cfg80211_rfkill_set_block).

So the rfkill is supposed to be wait for cleanup, not a forceful
shutdown of RF traffic? I assume it would be the later since to do a
proper cleanup that could cause more RF traffic while the current
assumption was to stop all traffic and then call hdev->shutdown to
ensure the driver does shutdown the RF traffic, perhaps this
assumption has changed over time since interrupting the RF traffic may
cause what you just described because the remote end will have to rely
on link-loss logic to detect the connection has been terminated.

> Signed-off-by: Jonas Dreßler <verdre@v0yd.nl>
> ---
>  net/bluetooth/hci_core.c | 33 ++++++++++++++++++++++++++++++---
>  1 file changed, 30 insertions(+), 3 deletions(-)
>
> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> index 1ec83985f..1c91d02f7 100644
> --- a/net/bluetooth/hci_core.c
> +++ b/net/bluetooth/hci_core.c
> @@ -543,6 +543,23 @@ int hci_dev_open(__u16 dev)
>         return err;
>  }
>
> +static int set_powered_off_sync(struct hci_dev *hdev, void *data)
> +{
> +       return hci_set_powered_sync(hdev, false);
> +}
> +
> +static void set_powered_off_sync_complete(struct hci_dev *hdev, void *data, int err)
> +{
> +       if (err)
> +               bt_dev_err(hdev, "Powering HCI device off before rfkilling failed (%d)", err);
> +}
> +
> +static int hci_dev_do_poweroff(struct hci_dev *hdev)
> +{
> +       return hci_cmd_sync_queue(hdev, set_powered_off_sync,
> +                                 NULL, set_powered_off_sync_complete);
> +}
> +
>  int hci_dev_do_close(struct hci_dev *hdev)
>  {
>         int err;
> @@ -943,17 +960,27 @@ int hci_get_dev_info(void __user *arg)
>  static int hci_rfkill_set_block(void *data, bool blocked)
>  {
>         struct hci_dev *hdev = data;
> +       int err;
>
>         BT_DBG("%p name %s blocked %d", hdev, hdev->name, blocked);
>
>         if (hci_dev_test_flag(hdev, HCI_USER_CHANNEL))
>                 return -EBUSY;
>
> +       if (blocked == hci_dev_test_flag(hdev, HCI_RFKILLED))
> +               return 0;
> +
>         if (blocked) {
> -               hci_dev_set_flag(hdev, HCI_RFKILLED);
>                 if (!hci_dev_test_flag(hdev, HCI_SETUP) &&
> -                   !hci_dev_test_flag(hdev, HCI_CONFIG))
> -                       hci_dev_do_close(hdev);
> +                   !hci_dev_test_flag(hdev, HCI_CONFIG)) {
> +                       err = hci_dev_do_poweroff(hdev);
> +                       if (err) {
> +                               bt_dev_err(hdev, "Powering off device before rfkilling failed (%d)",
> +                                          err);
> +                       }

You already have the error printed on set_powered_off_sync_complete
not sure why you have it here as well.

> +               }
> +
> +               hci_dev_set_flag(hdev, HCI_RFKILLED);

Before we used to set the HCI_RFKILLED beforehand, is this change
really intended or not? I think we should keep doing it ahead of power
off sequence since we can probably use it to ignore if there are any
errors on the cleanup, etc.

>         } else {
>                 hci_dev_clear_flag(hdev, HCI_RFKILLED);
>         }
> --
> 2.43.0
>
  

On 1/2/24 19:31, Luiz Augusto von Dentz wrote:
> Hi Jonas,
> 
> On Tue, Jan 2, 2024 at 1:19 PM Jonas Dreßler <verdre@v0yd.nl> wrote:
>>
>> On a lot of platforms (at least the MS Surface devices, M1 macbooks, and
>> a few ThinkPads) firmware doesn't do its job when rfkilling a device
>> and the bluetooth adapter is not actually shut down on rfkill. This leads
>> to connected devices remaining in connected state and the bluetooth
>> connection eventually timing out after rfkilling an adapter.
>>
>> Use the rfkill hook in the HCI driver to actually power the device off
>> before rfkilling it.
>>
>> Note that the wifi subsystem is doing something similar by calling
>> cfg80211_shutdown_all_interfaces()
>> in it's rfkill set_block callback (see cfg80211_rfkill_set_block).
> 
> So the rfkill is supposed to be wait for cleanup, not a forceful
> shutdown of RF traffic? I assume it would be the later since to do a
> proper cleanup that could cause more RF traffic while the current
> assumption was to stop all traffic and then call hdev->shutdown to
> ensure the driver does shutdown the RF traffic, perhaps this
> assumption has changed over time since interrupting the RF traffic may
> cause what you just described because the remote end will have to rely
> on link-loss logic to detect the connection has been terminated.

Yes, it seems to me that as soon as the rfkill happens, anything in the 
drivers hdev->shutdown to shut things down will no longer go through to 
the card. I'd assume this is something that's enforced by firmware and 
we can't change, or would that be a bug on our side?

But yeah, proper shutdown of the adapter requires a bit more RF traffic. 
If rfkill guarantees that it shuts down all RF traffic *immediately*, 
maybe it would be better to expect power-off MGMT commands from 
userspace before rfkilling? But given that the disconnect appears to 
happen fine on some hardware, this seemed like the obvious and more 
reliable way to me.

> 
>> Signed-off-by: Jonas Dreßler <verdre@v0yd.nl>
>> ---
>>   net/bluetooth/hci_core.c | 33 ++++++++++++++++++++++++++++++---
>>   1 file changed, 30 insertions(+), 3 deletions(-)
>>
>> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
>> index 1ec83985f..1c91d02f7 100644
>> --- a/net/bluetooth/hci_core.c
>> +++ b/net/bluetooth/hci_core.c
>> @@ -543,6 +543,23 @@ int hci_dev_open(__u16 dev)
>>          return err;
>>   }
>>
>> +static int set_powered_off_sync(struct hci_dev *hdev, void *data)
>> +{
>> +       return hci_set_powered_sync(hdev, false);
>> +}
>> +
>> +static void set_powered_off_sync_complete(struct hci_dev *hdev, void *data, int err)
>> +{
>> +       if (err)
>> +               bt_dev_err(hdev, "Powering HCI device off before rfkilling failed (%d)", err);
>> +}
>> +
>> +static int hci_dev_do_poweroff(struct hci_dev *hdev)
>> +{
>> +       return hci_cmd_sync_queue(hdev, set_powered_off_sync,
>> +                                 NULL, set_powered_off_sync_complete);
>> +}
>> +
>>   int hci_dev_do_close(struct hci_dev *hdev)
>>   {
>>          int err;
>> @@ -943,17 +960,27 @@ int hci_get_dev_info(void __user *arg)
>>   static int hci_rfkill_set_block(void *data, bool blocked)
>>   {
>>          struct hci_dev *hdev = data;
>> +       int err;
>>
>>          BT_DBG("%p name %s blocked %d", hdev, hdev->name, blocked);
>>
>>          if (hci_dev_test_flag(hdev, HCI_USER_CHANNEL))
>>                  return -EBUSY;
>>
>> +       if (blocked == hci_dev_test_flag(hdev, HCI_RFKILLED))
>> +               return 0;
>> +
>>          if (blocked) {
>> -               hci_dev_set_flag(hdev, HCI_RFKILLED);
>>                  if (!hci_dev_test_flag(hdev, HCI_SETUP) &&
>> -                   !hci_dev_test_flag(hdev, HCI_CONFIG))
>> -                       hci_dev_do_close(hdev);
>> +                   !hci_dev_test_flag(hdev, HCI_CONFIG)) {
>> +                       err = hci_dev_do_poweroff(hdev);
>> +                       if (err) {
>> +                               bt_dev_err(hdev, "Powering off device before rfkilling failed (%d)",
>> +                                          err);
>> +                       }
> 
> You already have the error printed on set_powered_off_sync_complete
> not sure why you have it here as well.
> 
>> +               }
>> +
>> +               hci_dev_set_flag(hdev, HCI_RFKILLED);
> 
> Before we used to set the HCI_RFKILLED beforehand, is this change
> really intended or not? I think we should keep doing it ahead of power
> off sequence since we can probably use it to ignore if there are any
> errors on the cleanup, etc.

Good point, it's been a while since I wrote that patch, maybe something 
in the power-off logic bails out if HCI_RFKILLED is set and that's why I 
moved it below, I'll check that...

> 
>>          } else {
>>                  hci_dev_clear_flag(hdev, HCI_RFKILLED);
>>          }
>> --
>> 2.43.0
>>
> 
>