netdev - Re: [PATCHv2 1/1] bluetooth: Check for SCO type before setting retransmission effort

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Message-Id: <AE7A1F22-766E-4C9B-A748-ACA5426B7DBD@holtmann.org>
Date:	Thu, 18 Sep 2014 08:43:40 -0700
From:	Marcel Holtmann <marcel@...tmann.org>
To:	Bernhard Thaler <bernhard.thaler@...t.at>
Cc:	"Gustavo F. Padovan" <gustavo@...ovan.org>,
	Johan Hedberg <johan.hedberg@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	BlueZ development <linux-bluetooth@...r.kernel.org>,
	Network Development <netdev@...r.kernel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 1/1] bluetooth: Check for SCO type before setting retransmission effort

Hi Bernhard,

> SCO connection cannot be setup to devices that do not support retransmission.
> Patch based on http://permalink.gmane.org/gmane.linux.bluez.kernel/7779 and
> adapted for this kernel version.
> Code changed to check SCO/eSCO type before setting retransmission effort
> and max. latency. The purpose of the patch is to support older devices not
> capable of eSCO.
> 
> Tested on Blackberry 655+ headset which does not support retransmission.
> Credits go to Alexander Sommerhuber.
> 
> Signed-off-by: Bernhard Thaler <bernhard.thaler@...t.at>
> ---
> net/bluetooth/hci_conn.c |   16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
> index faff624..f6e3183 100644
> --- a/net/bluetooth/hci_conn.c
> +++ b/net/bluetooth/hci_conn.c
> @@ -194,10 +194,18 @@ bool hci_setup_sync(struct hci_conn *conn, __u16 handle)
> 		param = &sco_param_wideband[conn->attempt - 1];
> 		break;
> 	case SCO_AIRMODE_CVSD:
> -		if (conn->attempt > ARRAY_SIZE(sco_param_cvsd))
> -			return false;
> -		cp.retrans_effort = 0x01;
> -		param = &sco_param_cvsd[conn->attempt - 1];
> +		if (!lmp_esco_capable(conn->link)) {
> +			/* sco_param_cvsd contains SCO in last two elements */
> +			if ((conn->attempt + 3) > ARRAY_SIZE(sco_param_cvsd))
> +				return false;
> +			cp.retrans_effort = 0xff;
> +			param = &sco_param_cvsd[(conn->attempt + 2)];

so if anybody creates a new mode and forgets to update this code, we are hitting a nice crash and/or wrong behavior.

I would prefer that we create separate parameter arrays here. It might means that we have to rename the current ones to esco_param_* and the introduce sco_param_cvsd.

> +		} else {
> +			if (conn->attempt > ARRAY_SIZE(sco_param_cvsd))
> +				return false;
> +			cp.retrans_effort = 0x01;
> +			param = &sco_param_cvsd[conn->attempt - 1];
> +		}
> 		break;
> 	default:
> 		return false;

Regards

Marcel

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