Date:   Wed, 25 Jan 2023 13:54:59 -0800
From:   Luiz Augusto von Dentz <luiz.dentz@...il.com>
To:     Zhengping Jiang <jiangzp@...gle.com>
Cc:     linux-bluetooth@...r.kernel.org, marcel@...tmann.org,
        chromeos-bluetooth-upstreaming@...omium.org,
        Archie Pusaka <apusaka@...omium.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [kernel PATCH v1 1/1] Bluetooth: Don't send HCI commands to
 remove adv if adapter is off

Hi Zhengping,

On Wed, Jan 25, 2023 at 1:12 PM Zhengping Jiang <jiangzp@...gle.com> wrote:
>
> From: Archie Pusaka <apusaka@...omium.org>
>
> Mark the advertisement as disabled when powering off the adapter
> without removing the advertisement, so they can be correctly
> re-enabled when adapter is powered on again.
>
> When adapter is off and user requested to remove advertisement,
> a HCI command will be issued. This causes the command to timeout
> and trigger GPIO reset.

Please include the btmon portion when the issue occurs.

> Therefore, immediately remove the advertisement without sending
> any HCI commands.
>
> Note that the above scenario only happens with extended advertisement
> (i.e. not using software rotation), because on the SW rotation
> scenario, we just wait until the rotation timer runs out before
> sending the HCI command. Since the timer is inactive when adapter is
> off, no HCI commands are sent.
>
> Signed-off-by: Archie Pusaka <apusaka@...omium.org>
> Signed-off-by: Zhengping Jiang <jiangzp@...gle.com>
>
> ---
>
> Changes in v1:
> - Mark the advertisement as disabled instead of clearing it.
> - Remove the advertisement without sending HCI command if the adapter is off.

Perhaps we should split these into 2 separated changes then, on top of
it it perhaps would be a good idea to implement a test in mgmt-tester
to check the correct behavior.

>  net/bluetooth/hci_sync.c | 57 +++++++++++++++++++++++++++++++++++++---
>  1 file changed, 53 insertions(+), 4 deletions(-)
>
> diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
> index 117eedb6f709..08da68a30acc 100644
> --- a/net/bluetooth/hci_sync.c
> +++ b/net/bluetooth/hci_sync.c
> @@ -1591,6 +1591,16 @@ int hci_remove_ext_adv_instance_sync(struct hci_dev *hdev, u8 instance,
>         if (!ext_adv_capable(hdev))
>                 return 0;
>
> +       /* When adapter is off, remove adv without sending HCI commands */
> +       if (!hdev_is_powered(hdev)) {
> +               hci_dev_lock(hdev);
> +               err = hci_remove_adv_instance(hdev, instance);
> +               if (!err)
> +                       mgmt_advertising_removed(sk, hdev, instance);

This code above is duplicated in a few places so we might as well have
it as a separate function e.g. hci_remove_adv

> +               hci_dev_unlock(hdev);
> +               return err;
> +       }
> +
>         err = hci_disable_ext_adv_instance_sync(hdev, instance);
>         if (err)
>                 return err;
> @@ -1772,6 +1782,23 @@ int hci_schedule_adv_instance_sync(struct hci_dev *hdev, u8 instance,
>         return hci_start_adv_sync(hdev, instance);
>  }
>
> +static void hci_clear_ext_adv_ins_during_power_off(struct hci_dev *hdev,
> +                                                  struct sock *sk)
> +{
> +       struct adv_info *adv, *n;
> +       int err;
> +
> +       hci_dev_lock(hdev);
> +       list_for_each_entry_safe(adv, n, &hdev->adv_instances, list) {
> +               u8 instance = adv->instance;
> +
> +               err = hci_remove_adv_instance(hdev, instance);
> +               if (!err)
> +                       mgmt_advertising_removed(sk, hdev, instance);

Then just call hci_remove_adv.

> +       }
> +       hci_dev_unlock(hdev);
> +}
> +
>  static int hci_clear_adv_sets_sync(struct hci_dev *hdev, struct sock *sk)
>  {
>         int err;
> @@ -1779,6 +1806,12 @@ static int hci_clear_adv_sets_sync(struct hci_dev *hdev, struct sock *sk)
>         if (!ext_adv_capable(hdev))
>                 return 0;
>
> +       /* When adapter is off, remove adv without sending HCI commands */
> +       if (!hdev_is_powered(hdev)) {
> +               hci_clear_ext_adv_ins_during_power_off(hdev, sk);

Use the remove to describe the action e.g. hci_remove_all_adv.

> +               return 0;
> +       }
> +
>         /* Disable instance 0x00 to disable all instances */
>         err = hci_disable_ext_adv_instance_sync(hdev, 0x00);
>         if (err)
> @@ -5177,9 +5210,27 @@ static int hci_disconnect_all_sync(struct hci_dev *hdev, u8 reason)
>         return 0;
>  }
>
> +static void hci_disable_ext_advertising_temporarily(struct hci_dev *hdev)
> +{
> +       struct adv_info *adv, *n;
> +
> +       if (!ext_adv_capable(hdev))
> +               return;
> +
> +       hci_dev_lock(hdev);
> +
> +       list_for_each_entry_safe(adv, n, &hdev->adv_instances, list)
> +               adv->enabled = false;
> +
> +       hci_dev_clear_flag(hdev, HCI_LE_ADV);
> +
> +       hci_dev_unlock(hdev);
> +}
> +
>  /* This function perform power off HCI command sequence as follows:
>   *
> - * Clear Advertising
> + * Disable Advertising Instances. Do not clear adv instances so advertising
> + * can be re-enabled on power on.
>   * Stop Discovery
>   * Disconnect all connections
>   * hci_dev_close_sync
> @@ -5199,9 +5250,7 @@ static int hci_power_off_sync(struct hci_dev *hdev)
>                         return err;
>         }
>
> -       err = hci_clear_adv_sync(hdev, NULL, false);
> -       if (err)
> -               return err;
> +       hci_disable_ext_advertising_temporarily(hdev);

Something like hci_disable_all_adv sounds better here.

>
>         err = hci_stop_discovery_sync(hdev);
>         if (err)
> --
> 2.39.1.456.gfc5497dd1b-goog
>


-- 
Luiz Augusto von Dentz

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