Re: [PATCH 6/6] Bluetooth: Support LE-Only discovery procedure

[Marcel Holtmann <marcel@holtmann.org>]

Hi Andre,

> This patch adds support for LE-Only discovery procedure through
> management interface.
> 
> Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
> ---
>  include/net/bluetooth/hci.h      |    1 +
>  include/net/bluetooth/hci_core.h |    1 +
>  net/bluetooth/hci_event.c        |   25 ++++++++++++++++++++++---
>  net/bluetooth/mgmt.c             |   25 +++++++++++++++++++++++--
>  4 files changed, 47 insertions(+), 5 deletions(-)
> 
> diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
> index bd3cecd..ca09998 100644
> --- a/include/net/bluetooth/hci.h
> +++ b/include/net/bluetooth/hci.h
> @@ -210,6 +210,7 @@ enum {
>  
>  #define LMP_EV4		0x01
>  #define LMP_EV5		0x02
> +#define LMP_NO_BREDR	0x20
>  #define LMP_LE		0x40
>  
>  #define LMP_SNIFF_SUBR	0x02
> diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
> index 9da5b69..55b78ec 100644
> --- a/include/net/bluetooth/hci_core.h
> +++ b/include/net/bluetooth/hci_core.h
> @@ -678,6 +678,7 @@ void hci_conn_del_sysfs(struct hci_conn *conn);
>  #define lmp_ssp_capable(dev)       ((dev)->features[6] & LMP_SIMPLE_PAIR)
>  #define lmp_no_flush_capable(dev)  ((dev)->features[6] & LMP_NO_FLUSH)
>  #define lmp_le_capable(dev)        ((dev)->features[4] & LMP_LE)
> +#define lmp_bredr_capable(dev)     (!((dev)->features[4] & LMP_NO_BREDR))

can you just split this into a separate patch first. We can just go
ahead and merge it.
 
>  /* ----- Extended LMP capabilities ----- */
>  #define lmp_host_le_capable(dev)   ((dev)->extfeatures[0] & LMP_HOST_LE)
> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> index dcbbffe..037c7c0 100644
> --- a/net/bluetooth/hci_event.c
> +++ b/net/bluetooth/hci_event.c
> @@ -954,24 +954,43 @@ static void hci_cc_le_set_scan_enable(struct hci_dev *hdev,
>  
>  	BT_DBG("%s status 0x%x", hdev->name, status);
>  
> -	if (status)
> -		return;
> -
>  	cp = hci_sent_cmd_data(hdev, HCI_OP_LE_SET_SCAN_ENABLE);
>  	if (!cp)
>  		return;
>  
>  	if (cp->enable == 0x01) {
> +		if (status) {
> +			hci_dev_lock(hdev);
> +			mgmt_start_discovery_failed(hdev, status);
> +			hci_dev_unlock(hdev);
> +			return;
> +		}
> +
>  		set_bit(HCI_LE_SCAN, &hdev->hci_flags);
>  
>  		del_timer(&hdev->adv_timer);
>  
>  		hci_dev_lock(hdev);
> +
> +		mgmt_discovering(hdev, 1);
> +
>  		hci_adv_entries_clear(hdev);
> +
>  		hci_dev_unlock(hdev);
>  	} else if (cp->enable == 0x00) {
> +		if (status) {
> +			hci_dev_lock(hdev);
> +			mgmt_stop_discovery_failed(hdev, status);
> +			hci_dev_unlock(hdev);
> +			return;
> +		}
> +
>  		clear_bit(HCI_LE_SCAN, &hdev->hci_flags);
>  
> +		hci_dev_lock(hdev);
> +		mgmt_discovering(hdev, 0);
> +		hci_dev_unlock(hdev);
> +
>  		mod_timer(&hdev->adv_timer, jiffies + ADV_CLEAR_TIMEOUT);
>  	}
>  }

This part looks fine to me.

> diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
> index b63a7d0..6ca6e5d 100644
> --- a/net/bluetooth/mgmt.c
> +++ b/net/bluetooth/mgmt.c
> @@ -32,7 +32,16 @@
>  #define MGMT_VERSION	0
>  #define MGMT_REVISION	1
>  
> -#define INQUIRY_LEN_BREDR 0x08 /* TGAP(100) */
> +/*
> + * These LE scan and inquiry parameters were chosen according to LE General
> + * Discovery Procedure specification.
> + */
> +#define LE_SCAN_TYPE 0x01
> +#define LE_SCAN_WIN 0x12
> +#define LE_SCAN_INT 0x12
> +#define LE_SCAN_TIMEOUT_LE_ONLY 10240		/* TGAP(gen_disc_scan_min) */
> +
> +#define INQUIRY_LEN_BREDR 0x08			/* TGAP(100) */
>  
>  struct pending_cmd {
>  	struct list_head list;
> @@ -1669,7 +1678,16 @@ static int start_discovery(struct sock *sk, u16 index)
>  		goto failed;
>  	}
>  
> -	err = hci_do_inquiry(hdev, INQUIRY_LEN_BREDR);
> +	if (lmp_host_le_capable(hdev)) {
> +		if (lmp_bredr_capable(hdev))
> +			err = -ENOSYS;
> +		else
> +			err = hci_do_le_scan(hdev, LE_SCAN_TYPE, LE_SCAN_INT,
> +					LE_SCAN_WIN, LE_SCAN_TIMEOUT_LE_ONLY);
> +	} else {
> +		err = hci_do_inquiry(hdev, INQUIRY_LEN_BREDR);
> +	}
> +
>  	if (err < 0)
>  		mgmt_pending_remove(cmd);
>  
> @@ -1701,6 +1719,9 @@ static int stop_discovery(struct sock *sk, u16 index)
>  	}
>  
>  	err = hci_cancel_inquiry(hdev);
> +	if (err == -EPERM)
> +		err = hci_cancel_le_scan(hdev);
> +

And here, I have a serious problem with how the code is done. I realize
that from using hdev->flags this ends up this crappy, but this is not
how I wanna see things done.

What you are doing is this:

- We call a complete unrelated function anyway
- And if it fails with a specific error code then we call something
  else instead

I think it becomes pretty obvious now that we should just have had
hdev->mgmt_flags that tell us with discovery procedure is running right
now. And thus we know how to cancel it.

Regards

Marcel