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Date:   Wed, 9 Sep 2020 13:06:15 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Joseph Hwang <josephsih@...omium.org>
Cc:     linux-bluetooth@...r.kernel.org, marcel@...tmann.org,
        luiz.dentz@...il.com, chromeos-bluetooth-upstreaming@...omium.org,
        josephsih@...gle.com, Alain Michaud <alainm@...omium.org>,
        Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2 1/2] Bluetooth: btusb: define HCI packet sizes of USB
 Alts

On Wednesday 09 September 2020 17:42:01 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 <alainm@...omium.org>
> Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
> Signed-off-by: Joseph Hwang <josephsih@...omium.org>
> ---
> 
> Changes in v2:
> - 1/2: Used sco_mtu instead of a new sco_pkt_len member in hdev.
> - 1/2: Do not overwrite hdev->sco_mtu in hci_cc_read_buffer_size
>   if it has been set in the USB interface.
> - 2/2: Used BT_SNDMTU/BT_RCVMTU instead of creating a new opt name.
> - 2/2: Used the existing conn->mtu instead of creating a new member
>        in struct sco_pinfo.
> - 2/2: Noted that the old SCO_OPTIONS in sco_sock_getsockopt_old()
>        would just work as it uses sco_pi(sk)->conn->mtu.
> 
>  drivers/bluetooth/btusb.c | 43 +++++++++++++++++++++++++++++----------
>  net/bluetooth/hci_event.c |  7 ++++++-
>  2 files changed, 38 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
> index fe80588c7bd3a8..a710233382afff 100644
> --- a/drivers/bluetooth/btusb.c
> +++ b/drivers/bluetooth/btusb.c
> @@ -459,6 +459,22 @@ 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)

Hello! What is value for 'suggested_max_packet_size' used in above
calculation algorithm?

> + */
> +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 +3975,15 @@ 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 +4047,10 @@ 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 +4092,6 @@ 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 +4103,10 @@ 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..b3e9247fdbcfa1 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -730,7 +730,12 @@ 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;
> +	/* Set sco_mtu only when not yet.
> +	 * The sco_mtu would be set in btusb.c
> +	 * if the host controller interface is USB.
> +	 */
> +	if (hdev->sco_mtu == 0)
> +		hdev->sco_mtu  = rp->sco_mtu;

Should not hdev->sco_mtu contains minimum from the rp->sco_mtu and your
calculated value defined in hci_packet_size_usb_alt[i]?

Socket MTU cannot be bigger then value rp->sco_mtu, right?

>  	hdev->acl_pkts = __le16_to_cpu(rp->acl_max_pkt);
>  	hdev->sco_pkts = __le16_to_cpu(rp->sco_max_pkt);
>  
> -- 
> 2.28.0.526.ge36021eeef-goog
> 

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