Re: [PATCH v5 3/3] Bluetooth: Add BT_MODE socket option

[Marcel Holtmann <marcel@holtmann.org>]

Hi Luiz,

>>> This adds BT_MODE socket option which can be used to set L2CAP modes,
>>> including modes only supported over LE which were not supported using
>>> the L2CAP_OPTIONS.
>>> 
>>> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
>>> ---
>>> include/net/bluetooth/bluetooth.h |   8 ++
>>> include/net/bluetooth/l2cap.h     |   6 ++
>>> net/bluetooth/l2cap_sock.c        | 124 ++++++++++++++++++++++++++++++
>>> 3 files changed, 138 insertions(+)
>>> 
>>> diff --git a/include/net/bluetooth/bluetooth.h b/include/net/bluetooth/bluetooth.h
>>> index 1576353a2773..3fa7b1e3c5d9 100644
>>> --- a/include/net/bluetooth/bluetooth.h
>>> +++ b/include/net/bluetooth/bluetooth.h
>>> @@ -139,6 +139,14 @@ struct bt_voice {
>>> #define BT_PHY_LE_CODED_TX    0x00002000
>>> #define BT_PHY_LE_CODED_RX    0x00004000
>>> 
>>> +#define BT_MODE                      15
>>> +
>>> +#define BT_MODE_BASIC                0x00
>>> +#define BT_MODE_ERTM         0x01
>>> +#define BT_MODE_STREAMING    0x02
>>> +#define BT_MODE_LE_FLOWCTL   0x03
>>> +#define BT_MODE_EXT_FLOWCTL  0x04
>>> +
>>> __printf(1, 2)
>>> void bt_info(const char *fmt, ...);
>>> __printf(1, 2)
>>> diff --git a/include/net/bluetooth/l2cap.h b/include/net/bluetooth/l2cap.h
>>> index dada14d0622c..56f727ba23bd 100644
>>> --- a/include/net/bluetooth/l2cap.h
>>> +++ b/include/net/bluetooth/l2cap.h
>>> @@ -720,9 +720,15 @@ struct l2cap_user {
>>> /* ----- L2CAP socket info ----- */
>>> #define l2cap_pi(sk) ((struct l2cap_pinfo *) sk)
>>> 
>>> +#define L2CAP_PI_OPTION_UNSET                0x00
>>> +#define L2CAP_PI_OPTION_LEGACY               0x01
>>> +#define L2CAP_PI_OPTION_BT_MODE              0x02
>>> +
>>> struct l2cap_pinfo {
>>>      struct bt_sock          bt;
>>>      struct l2cap_chan       *chan;
>>> +     u8                      option;
>>> +     u8                      bt_mode;
>>>      struct sk_buff          *rx_busy_skb;
>>> };
>> 
>> why do you want to store bt_mode here. Whatever we have in l2cap_chan should be plenty.
> 
> Ive thought it would be cleaner to mess with types that comes from the
> spec itself so l2cap_chan would continue to use them.

Actually the LE_FLOWCTL and EXT_FLOWCTL are not spec values either. Frankly I don’t care which ones we store right now. I am fine keeping the spec one for now and just translate it to BT_MODE.

>> I also looked at l2cap_sock_setsockopt_old and if you use L2CAP_OPTIONS and want to read BT_MODE, then everything should be fine. Same as setting BT_MODE (except EXT_FLOWCTL) and then reading L2CAP_OPTIONS is fine as well. We can all translate this properly and with have EINVAL return errors for not supported / disabled modes.
>> 
>> So the only time L2CAP_OPTIONS read should fail is if you use BT_MODE with EXT_FLOWCTL as mode. So you can just check the mode set in l2cap_chan. And we start using our new mode definition there and then convert it for L2CAP_OPTIONS.
> 
> Sure, I thought it would be more efficient to not have conversions
> back and forth but Im fine either way.

In the end it makes the code simpler to just do the conversion. And once we add a kernel option to disable setsockopt_old, we have less code.

Regards

Marcel