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 <9F696602-8BAC-479E-998D-118DDAE54445@holtmann.org>
In-Reply-To: <9F696602-8BAC-479E-998D-118DDAE54445@holtmann.org>
From:   Joseph Hwang <josephsih@google.com>
Date:   Sat, 5 Mar 2022 15:42:16 +0800
Message-ID: <CAHFy41-DMxGo_Lc=k2kUU_fsAjdNt6o+KHTPJupas8EetdCUdw@mail.gmail.com>
Subject: Re: [PATCH v4 1/3] Bluetooth: aosp: surface AOSP quality report
 through mgmt
To:     Marcel Holtmann <marcel@holtmann.org>
Cc:     BlueZ <linux-bluetooth@vger.kernel.org>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        =?UTF-8?Q?Pali_Roh=C3=A1r?= <pali@kernel.org>,
        CrosBT Upstreaming <chromeos-bluetooth-upstreaming@chromium.org>,
        Archie Pusaka <apusaka@chromium.org>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>, netdev@vger.kernel.org
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Hi Marcel, thank you for reviewing the patches! I have some questions
and would like to confirm with you. Please read my replies in the
lines below. Thanks!

On Thu, Feb 17, 2022 at 8:41 PM Marcel Holtmann <marcel@holtmann.org> wrote=
:
>
> Hi Joseph,
>
> > When receiving a HCI vendor event, the kernel checks if it is an
> > AOSP bluetooth quality report. If yes, the event is sent to bluez
> > user space through the mgmt socket.
> >
> > Signed-off-by: Joseph Hwang <josephsih@chromium.org>
> > Reviewed-by: Archie Pusaka <apusaka@chromium.org>
> > ---
> >
> > (no changes since v3)
> >
> > Changes in v3:
> > - Rebase to resolve the code conflict.
> > - Move aosp_quality_report_evt() from hci_event.c to aosp.c.
> > - A new patch (3/3) is added to enable the quality report feature.
> >
> > Changes in v2:
> > - Scrap the two structures defined in aosp.c and use constants for
> >  size check.
> > - Do a basic size check about the quality report event. Do not pull
> >  data from the event in which the kernel has no interest.
> > - Define vendor event prefixes with which vendor events of distinct
> >  vendor specifications can be clearly differentiated.
> > - Use mgmt helpers to add the header and data to a mgmt skb.
>
> this unsolicited vendor event business is giving me a headache. I assume =
it would be a lot simpler, but it doesn=E2=80=99t look like this. I need to=
 spent some rounds of thinking to give you good advice. Unfortunately since=
 we also want to support Intel vendor specific pieces, this is getting supe=
r complicated.

You have mentioned using hdev->hci_recv_quality_report to send the
unsolicited events from the Intel driver in your comments in Patch
2/3. Just would like to confirm with you. Thanks.

>
> > include/net/bluetooth/hci_core.h |  5 ++
> > include/net/bluetooth/mgmt.h     |  7 +++
> > net/bluetooth/aosp.c             | 27 ++++++++++
> > net/bluetooth/aosp.h             | 13 +++++
> > net/bluetooth/hci_event.c        | 84 +++++++++++++++++++++++++++++++-
> > net/bluetooth/mgmt.c             | 20 ++++++++
> > net/bluetooth/msft.c             | 14 ++++++
> > net/bluetooth/msft.h             | 12 +++++
> > 8 files changed, 181 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/h=
ci_core.h
> > index f5caff1ddb29..ea83619ac4de 100644
> > --- a/include/net/bluetooth/hci_core.h
> > +++ b/include/net/bluetooth/hci_core.h
> > @@ -1864,6 +1864,8 @@ int mgmt_add_adv_patterns_monitor_complete(struct=
 hci_dev *hdev, u8 status);
> > int mgmt_remove_adv_monitor_complete(struct hci_dev *hdev, u8 status);
> > void mgmt_adv_monitor_device_lost(struct hci_dev *hdev, u16 handle,
> >                                 bdaddr_t *bdaddr, u8 addr_type);
> > +int mgmt_quality_report(struct hci_dev *hdev, void *data, u32 data_len=
,
> > +                     u8 quality_spec);
> >
> > u8 hci_le_conn_update(struct hci_conn *conn, u16 min, u16 max, u16 late=
ncy,
> >                     u16 to_multiplier);
> > @@ -1882,4 +1884,7 @@ void hci_copy_identity_address(struct hci_dev *hd=
ev, bdaddr_t *bdaddr,
> >
> > #define TRANSPORT_TYPE_MAX    0x04
> >
> > +#define QUALITY_SPEC_AOSP_BQR                0x0
> > +#define QUALITY_SPEC_INTEL_TELEMETRY 0x1
> > +
> > #endif /* __HCI_CORE_H */
> > diff --git a/include/net/bluetooth/mgmt.h b/include/net/bluetooth/mgmt.=
h
> > index 3d26e6a3478b..83b602636262 100644
> > --- a/include/net/bluetooth/mgmt.h
> > +++ b/include/net/bluetooth/mgmt.h
> > @@ -1120,3 +1120,10 @@ struct mgmt_ev_adv_monitor_device_lost {
> >       __le16 monitor_handle;
> >       struct mgmt_addr_info addr;
> > } __packed;
> > +
> > +#define MGMT_EV_QUALITY_REPORT                       0x0031
> > +struct mgmt_ev_quality_report {
> > +     __u8    quality_spec;
> > +     __u32   data_len;
> > +     __u8    data[];
> > +} __packed;
> > diff --git a/net/bluetooth/aosp.c b/net/bluetooth/aosp.c
> > index 432ae3aac9e3..4a336433180d 100644
> > --- a/net/bluetooth/aosp.c
> > +++ b/net/bluetooth/aosp.c
> > @@ -199,3 +199,30 @@ int aosp_set_quality_report(struct hci_dev *hdev, =
bool enable)
> >       else
> >               return disable_quality_report(hdev);
> > }
> > +
> > +#define BLUETOOTH_QUALITY_REPORT_EV          0x58
> > +
> > +/* The following LEN =3D 1-byte Sub-event code + 48-byte Sub-event Par=
ameters */
> > +#define BLUETOOTH_QUALITY_REPORT_LEN         49
> > +
> > +bool aosp_check_quality_report_len(struct sk_buff *skb)
> > +{
> > +     /* skb->len is allowed to be larger than BLUETOOTH_QUALITY_REPORT=
_LEN
> > +      * to accommodate an additional Vendor Specific Parameter (vsp) f=
ield.
> > +      */
> > +     if (skb->len < BLUETOOTH_QUALITY_REPORT_LEN) {
> > +             BT_ERR("AOSP evt data len %d too short (%u expected)",
> > +                    skb->len, BLUETOOTH_QUALITY_REPORT_LEN);
> > +             return false;
> > +     }
> > +
> > +     return true;
> > +}
> > +
> > +void aosp_quality_report_evt(struct hci_dev *hdev,  void *data,
> > +                          struct sk_buff *skb)
> > +{
> > +     if (aosp_has_quality_report(hdev) && aosp_check_quality_report_le=
n(skb))
> > +             mgmt_quality_report(hdev, skb->data, skb->len,
> > +                                 QUALITY_SPEC_AOSP_BQR);
> > +}
> > diff --git a/net/bluetooth/aosp.h b/net/bluetooth/aosp.h
> > index 2fd8886d51b2..b21751e012de 100644
> > --- a/net/bluetooth/aosp.h
> > +++ b/net/bluetooth/aosp.h
> > @@ -10,6 +10,9 @@ void aosp_do_close(struct hci_dev *hdev);
> >
> > bool aosp_has_quality_report(struct hci_dev *hdev);
> > int aosp_set_quality_report(struct hci_dev *hdev, bool enable);
> > +bool aosp_check_quality_report_len(struct sk_buff *skb);
> > +void aosp_quality_report_evt(struct hci_dev *hdev,  void *data,
> > +                          struct sk_buff *skb);
> >
> > #else
> >
> > @@ -26,4 +29,14 @@ static inline int aosp_set_quality_report(struct hci=
_dev *hdev, bool enable)
> >       return -EOPNOTSUPP;
> > }
> >
> > +static inline bool aosp_check_quality_report_len(struct sk_buff *skb)
> > +{
> > +     return false;
> > +}
> > +
> > +static inline void aosp_quality_report_evt(struct hci_dev *hdev,  void=
 *data,
> > +                                        struct sk_buff *skb)
> > +{
> > +}
> > +
> > #endif
> > diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
> > index 63b925921c87..6468ea0f71bd 100644
> > --- a/net/bluetooth/hci_event.c
> > +++ b/net/bluetooth/hci_event.c
> > @@ -37,6 +37,7 @@
> > #include "smp.h"
> > #include "msft.h"
> > #include "eir.h"
> > +#include "aosp.h"
> >
> > #define ZERO_KEY "\x00\x00\x00\x00\x00\x00\x00\x00" \
> >                "\x00\x00\x00\x00\x00\x00\x00\x00"
> > @@ -4241,6 +4242,87 @@ static void hci_num_comp_blocks_evt(struct hci_d=
ev *hdev, void *data,
> >       queue_work(hdev->workqueue, &hdev->tx_work);
> > }
> >
> > +/* Define the fixed vendor event prefixes below.
> > + * Note: AOSP HCI Requirements use 0x54 and up as sub-event codes with=
out
> > + *       actually defining a vendor prefix. Refer to
> > + *       https://source.android.com/devices/bluetooth/hci_requirements
> > + *       Hence, the other vendor event prefixes should not use the sam=
e
> > + *       space to avoid collision.
> > + */
> > +static unsigned char AOSP_BQR_PREFIX[] =3D { 0x58 };
> > +
> > +/* Some vendor prefixes are fixed values and lengths. */
> > +#define FIXED_EVT_PREFIX(_prefix, _vendor_func)                       =
       \
> > +{                                                                    \
> > +     .prefix =3D _prefix,                                             =
 \
> > +     .prefix_len =3D sizeof(_prefix),                                 =
 \
> > +     .vendor_func =3D _vendor_func,                                   =
 \
> > +     .get_prefix =3D NULL,                                            =
 \
> > +     .get_prefix_len =3D NULL,                                        =
 \
> > +}
> > +
> > +/* Some vendor prefixes are only available at run time. The
> > + * values and lengths are variable.
> > + */
> > +#define DYNAMIC_EVT_PREFIX(_prefix_func, _prefix_len_func, _vendor_fun=
c)\
> > +{                                                                    \
> > +     .prefix =3D NULL,                                                =
 \
> > +     .prefix_len =3D 0,                                               =
 \
> > +     .vendor_func =3D _vendor_func,                                   =
 \
> > +     .get_prefix =3D _prefix_func,                                    =
 \
> > +     .get_prefix_len =3D _prefix_len_func,                            =
 \
> > +}
> > +
> > +/* Every distinct vendor specification must have a well-defined vendor
> > + * event prefix to determine if a vendor event meets the specification=
.
> > + * If an event prefix is fixed, it should be delcared with FIXED_EVT_P=
REFIX.
> > + * Otherwise, DYNAMIC_EVT_PREFIX should be used for variable prefixes.
> > + */
> > +struct vendor_event_prefix {
> > +     __u8 *prefix;
> > +     __u8 prefix_len;
> > +     void (*vendor_func)(struct hci_dev *hdev, void *data,
> > +                         struct sk_buff *skb);
> > +     __u8 *(*get_prefix)(struct hci_dev *hdev);
> > +     __u8 (*get_prefix_len)(struct hci_dev *hdev);
> > +} evt_prefixes[] =3D {
> > +     FIXED_EVT_PREFIX(AOSP_BQR_PREFIX, aosp_quality_report_evt),
> > +     DYNAMIC_EVT_PREFIX(get_msft_evt_prefix, get_msft_evt_prefix_len,
> > +                        msft_vendor_evt),
> > +
> > +     /* end with a null entry */
> > +     {},
> > +};
> > +
> > +static void hci_vendor_evt(struct hci_dev *hdev, void *data,
> > +                        struct sk_buff *skb)
> > +{
> > +     int i;
> > +     __u8 *prefix;
> > +     __u8 prefix_len;
> > +
> > +     for (i =3D 0; evt_prefixes[i].vendor_func; i++) {
> > +             if (evt_prefixes[i].get_prefix)
> > +                     prefix =3D evt_prefixes[i].get_prefix(hdev);
> > +             else
> > +                     prefix =3D evt_prefixes[i].prefix;
> > +
> > +             if (evt_prefixes[i].get_prefix_len)
> > +                     prefix_len =3D evt_prefixes[i].get_prefix_len(hde=
v);
> > +             else
> > +                     prefix_len =3D evt_prefixes[i].prefix_len;
> > +
> > +             if (!prefix || prefix_len =3D=3D 0)
> > +                     continue;
> > +
> > +             /* Compare the raw prefix data directly. */
> > +             if (!memcmp(prefix, skb->data, prefix_len)) {
> > +                     evt_prefixes[i].vendor_func(hdev, data, skb);
> > +                     break;
> > +             }
> > +     }
> > +}
> > +
> > static void hci_mode_change_evt(struct hci_dev *hdev, void *data,
> >                               struct sk_buff *skb)
> > {
> > @@ -6844,7 +6926,7 @@ static const struct hci_ev {
> >       HCI_EV(HCI_EV_NUM_COMP_BLOCKS, hci_num_comp_blocks_evt,
> >              sizeof(struct hci_ev_num_comp_blocks)),
> >       /* [0xff =3D HCI_EV_VENDOR] */
> > -     HCI_EV_VL(HCI_EV_VENDOR, msft_vendor_evt, 0, HCI_MAX_EVENT_SIZE),
> > +     HCI_EV_VL(HCI_EV_VENDOR, hci_vendor_evt, 0, HCI_MAX_EVENT_SIZE),
> > };
>
> I was thinking along the lines like this:
>
>         HCI_EV_VND(evt_prefix, evt_prefix_len, callback),
>
> So that we in the end can do things like this:
>
>         HCI_EV_VL({ 0x58 }, 1, aosp_quality_report_evt),
>

I wish I could use a macro as simple as HCI_EV_VND(evt_prefix,
evt_prefix_len, callback). However, I do not have a clean method to
handle the dynamic msft vendor prefix of which the value and length
are not known until runtime. Do you have any suggestions here?

>
>
> >
> > static void hci_event_func(struct hci_dev *hdev, u8 event, struct sk_bu=
ff *skb,
> > diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
> > index 914e2f2d3586..5e48576041fb 100644
> > --- a/net/bluetooth/mgmt.c
> > +++ b/net/bluetooth/mgmt.c
> > @@ -4389,6 +4389,26 @@ static int set_exp_feature(struct sock *sk, stru=
ct hci_dev *hdev,
> >                              MGMT_STATUS_NOT_SUPPORTED);
> > }
> >
> > +int mgmt_quality_report(struct hci_dev *hdev, void *data, u32 data_len=
,
> > +                     u8 quality_spec)
> > +{
> > +     struct mgmt_ev_quality_report *ev;
> > +     struct sk_buff *skb;
> > +
> > +     skb =3D mgmt_alloc_skb(hdev, MGMT_EV_QUALITY_REPORT,
> > +                          sizeof(*ev) + data_len);
> > +     if (!skb)
> > +             return -ENOMEM;
> > +
> > +     ev =3D skb_put(skb, sizeof(*ev));
> > +     ev->quality_spec =3D quality_spec;
> > +     ev->data_len =3D data_len;
> > +     skb_put_data(skb, data, data_len);
> > +
> > +     return mgmt_event_skb(skb, NULL);
> > +}
> > +EXPORT_SYMBOL(mgmt_quality_report);
> > +
>
> I know what you want to do, but I can not let you call mgmt_ function fro=
m a driver. We need to make this cleaner and abstract so that the driver ha=
s a proper path to report it to hci_core and that decides then to send the =
report or not.

Will set up hdev->hci_recv_quality_report as you mentioned in comments
in Patch 2/3.

>
>
> > static int get_device_flags(struct sock *sk, struct hci_dev *hdev, void=
 *data,
> >                           u16 data_len)
> > {
> > diff --git a/net/bluetooth/msft.c b/net/bluetooth/msft.c
> > index 9a3d77d3ca86..3edf64baf479 100644
> > --- a/net/bluetooth/msft.c
> > +++ b/net/bluetooth/msft.c
> > @@ -731,6 +731,20 @@ static void msft_monitor_device_evt(struct hci_dev=
 *hdev, struct sk_buff *skb)
> >                                handle_data->mgmt_handle);
> > }
> >
> > +__u8 *get_msft_evt_prefix(struct hci_dev *hdev)
> > +{
> > +     struct msft_data *msft =3D hdev->msft_data;
> > +
> > +     return msft->evt_prefix;
> > +}
> > +
> > +__u8 get_msft_evt_prefix_len(struct hci_dev *hdev)
> > +{
> > +     struct msft_data *msft =3D hdev->msft_data;
> > +
> > +     return msft->evt_prefix_len;
> > +}
> > +
>
> So I wonder if this should be moved directly into hci_dev under CONFIG_BT=
_MSFTEXT check. Luiz also needs to have a look at this. This is unfortunate=
ly getting a bit nasty now. We need to find a clean solution, otherwise the=
 next vendor thing is blowing up in our face.

My understanding is that static inline hci_set_msft_opcode() under
CONFIG_BT_MSFTEXT is placed in hci_core.h because drivers need to call
it. Here, get_msft_evt_prefix() and get_msft_evt_prefix_len() are not
to be called by drivers. Do we still need to move them into
hci_core.h? Please let me know if I have any misunderstanding. Thanks.

>
>
> > void msft_vendor_evt(struct hci_dev *hdev, void *data, struct sk_buff *=
skb)
> > {
> >       struct msft_data *msft =3D hdev->msft_data;
> > diff --git a/net/bluetooth/msft.h b/net/bluetooth/msft.h
> > index afcaf7d3b1cb..a354ebf61fed 100644
> > --- a/net/bluetooth/msft.h
> > +++ b/net/bluetooth/msft.h
> > @@ -27,6 +27,8 @@ int msft_set_filter_enable(struct hci_dev *hdev, bool=
 enable);
> > int msft_suspend_sync(struct hci_dev *hdev);
> > int msft_resume_sync(struct hci_dev *hdev);
> > bool msft_curve_validity(struct hci_dev *hdev);
> > +__u8 *get_msft_evt_prefix(struct hci_dev *hdev);
> > +__u8 get_msft_evt_prefix_len(struct hci_dev *hdev);
> >
> > #else
> >
> > @@ -77,4 +79,14 @@ static inline bool msft_curve_validity(struct hci_de=
v *hdev)
> >       return false;
> > }
> >
> > +static inline __u8 *get_msft_evt_prefix(struct hci_dev *hdev)
> > +{
> > +     return NULL;
> > +}
> > +
> > +static inline __u8 get_msft_evt_prefix_len(struct hci_dev *hdev)
> > +{
> > +     return 0;
> > +}
> > +
> > #endif
>
> Regards
>
> Marcel
>

Regards,
--=20

Joseph Shyh-In Hwang
Email: josephsih@google.com