linux-kernel - Re: [PATCHv3 1/1] bluetooth: Check for SCO type before setting retransmission effort

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Message-Id: <736161F0-DA1F-4AD4-B74A-22FCAB58B23F@holtmann.org>
Date:	Tue, 23 Sep 2014 09:44:33 +0200
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>,
	linux-bluetooth@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 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 |   22 +++++++++++++++++-----
> 1 file changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/net/bluetooth/hci_conn.c b/net/bluetooth/hci_conn.c
> index faff624..32dcde1 100644
> --- a/net/bluetooth/hci_conn.c
> +++ b/net/bluetooth/hci_conn.c
> @@ -38,7 +38,7 @@ struct sco_param {
> 	u16 max_latency;
> };
> 
> -static const struct sco_param sco_param_cvsd[] = {
> +static const struct sco_param esco_param_cvsd[] = {
> 	{ EDR_ESCO_MASK & ~ESCO_2EV3, 0x000a }, /* S3 */
> 	{ EDR_ESCO_MASK & ~ESCO_2EV3, 0x0007 }, /* S2 */
> 	{ EDR_ESCO_MASK | ESCO_EV3,   0x0007 }, /* S1 */
> @@ -46,6 +46,11 @@ static const struct sco_param sco_param_cvsd[] = {
> 	{ EDR_ESCO_MASK | ESCO_HV1,   0xffff }, /* D0 */
> };
> 
> +static const struct sco_param sco_param_cvsd[] = {
> +	{ EDR_ESCO_MASK | ESCO_HV3,   0xffff }, /* D1 */
> +	{ EDR_ESCO_MASK | ESCO_HV1,   0xffff }, /* D0 */
> +};
> +
> static const struct sco_param sco_param_wideband[] = {
> 	{ EDR_ESCO_MASK & ~ESCO_2EV3, 0x000d }, /* T2 */
> 	{ EDR_ESCO_MASK | ESCO_EV3,   0x0008 }, /* T1 */
> @@ -194,10 +199,17 @@ 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)) {

please change this statement around to check if eSCO support exists and not if it does not exist. The negation is pointless if you have an else branch anyway.

> +			if ((conn->attempt) > ARRAY_SIZE(sco_param_cvsd))

The extra (conn->attempt) is not needed. Just do (conn->attempt > ARRAY_SIZE(..))

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

The rest looks fine.

Regards

Marcel

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