Hi Marcel,
On Mon, Jun 22, 2020 at 12:14 AM Marcel Holtmann <marcel@xxxxxxxxxxxx> wrote:
>
> Hi Alain,
>
> >>>> please use “Bluetooth: “ prefix for the subject.
> >>>
> >>> ack.
> >>>>
> >>>>
> >>>>> When the extended advertisement feature is enabled, a hardcoded min and
> >>>>> max interval of 0x8000 is used. This patches fixes this issue by using
> >>>>> the configured min/max value.
> >>>>>
> >>>>> This was validated by setting min/max in main.conf and making sure the
> >>>>> right setting is applied:
> >>>>>
> >>>>> < HCI Command: LE Set Extended Advertising Parameters (0x08|0x0036) plen
> >>>>> 25 #93 [hci0] 10.953011
> >>>>> …
> >>>>> Min advertising interval: 181.250 msec (0x0122)
> >>>>> Max advertising interval: 181.250 msec (0x0122)
> >>>>> …
> >>>>>
> >>>>> Reviewed-by: Abhishek Pandit-Subedi <abhishekpandit@xxxxxxxxxxxx>
> >>>>> Reviewed-by: Daniel Winkler <danielwinkler@xxxxxxxxxx>
> >>>>>
> >>>>> Signed-off-by: Alain Michaud <alainm@xxxxxxxxxxxx>
> >>>>
> >>>> The Reviewed-by lines go after your Signed-off-by.
> >>>
> >>> ack.
> >>>>
> >>>>
> >>>>> ---
> >>>>>
> >>>>> net/bluetooth/hci_request.c | 10 ++++++----
> >>>>> 1 file changed, 6 insertions(+), 4 deletions(-)
> >>>>>
> >>>>> diff --git a/net/bluetooth/hci_request.c b/net/bluetooth/hci_request.c
> >>>>> index 29decd7e8051..08818b9bf89f 100644
> >>>>> --- a/net/bluetooth/hci_request.c
> >>>>> +++ b/net/bluetooth/hci_request.c
> >>>>> @@ -1799,8 +1799,9 @@ int __hci_req_setup_ext_adv_instance(struct hci_request *req, u8 instance)
> >>>>> int err;
> >>>>> struct adv_info *adv_instance;
> >>>>> bool secondary_adv;
> >>>>> - /* In ext adv set param interval is 3 octets */
> >>>>> - const u8 adv_interval[3] = { 0x00, 0x08, 0x00 };
> >>>>> + /* In ext adv set param interval is 3 octets in le format */
> >>>>> + const __le32 min_adv_interval = cpu_to_le32(hdev->le_adv_min_interval);
> >>>>> + const __le32 max_adv_interval = cpu_to_le32(hdev->le_adv_max_interval);
> >>>>
> >>>> Scrap the const here.
> >>>
> >>> I'd like to understand why it isn't prefered to use const when you
> >>> don't intend to modify it in the code.
> >>>>
> >>>>
> >>>> And it is wrong since your hdev->le_adv_{min,max}_interval is actually __u16. So that first needs to be extended to a __u16 value.
> >>>
> >>> The macro actually leads to a function call that has a __u32 as a
> >>> parameter so the __u16 gets upcasted to a __u32 already.
> >>>>
> >>>>
> >>>> That said, if we have this in the Load Default System Configuration list, we should extended it to __le32 there as well.
> >>>
> >>> I agree, this means the range of default system configuration may not
> >>> be sufficient to accept all possible values that the newer command
> >>> supports, although I think this is a separate issue from what this
> >>> patch is trying to solve.
> >>>>
> >>>>
> >>>>> if (instance > 0) {
> >>>>> adv_instance = hci_find_adv_instance(hdev, instance);
> >>>>> @@ -1833,8 +1834,9 @@ int __hci_req_setup_ext_adv_instance(struct hci_request *req, u8 instance)
> >>>>>
> >>>>> memset(&cp, 0, sizeof(cp));
> >>>>>
> >>>>> - memcpy(cp.min_interval, adv_interval, sizeof(cp.min_interval));
> >>>>> - memcpy(cp.max_interval, adv_interval, sizeof(cp.max_interval));
> >>>>> + /* take least significant 3 bytes */
> >>>>> + memcpy(cp.min_interval, &min_adv_interval, sizeof(cp.min_interval));
> >>>>> + memcpy(cp.max_interval, &max_adv_interval, sizeof(cp.max_interval));
> >>>>
> >>>> This is dangerous and I think it actually break in case of unaligned access platforms.
> >>>
> >>> Since it is in le format already and the 3 bytes from the cmd struct
> >>> are raw, I'm not sure how this can be dangerous. It effectively
> >>> yields the exact same results as your suggestions below.
> >>
> >> In zephyr we end up doing helper functions for 24 bits:
> >>
> >> https://github.com/zephyrproject-rtos/zephyr/blob/master/include/sys/byteorder.h#L316
> >>
> >> I guess that is safer in terms of alignment access and it would work
> >> independent of the host order which apparently was not the case in the
> >> code above since it doesn't do the conversion to le32 (or perhaps the
> >> intervals are already in le32), anyway having something like that is
> >> probably much simpler to maintain given that most intervals use for
> >> things like ISO are also 24 bits long.
> > I like this. Would you put this in hci.h or keep to a lower scope?
> >
> > static inline void hci_cpu_to_le24(__u32 val, __u8 dst[3])
> > {
> > dst[0] = val & 0xff;
> > dst[1] = (val & 0xff00) >> 8;
> > dst[2] = (val & 0xff0000) >> 16;
> > }
>
> hmmm, how many 24-bit fields do we have in Bluetooth HCI spec? If it is just one, then lets keep it close to the usage, if not, I have also no object to put it in a higher level.
These are the instances of 24-bit fields:
include/net/bluetooth/hci.h: __u8 min_interval[3];
include/net/bluetooth/hci.h: __u8 max_interval[3];
include/net/bluetooth/hci.h: __u8 m_interval[3];
include/net/bluetooth/hci.h: __u8 s_interval[3];
include/net/bluetooth/hci.h: __u8 cig_sync_delay[3];
include/net/bluetooth/hci.h: __u8 cis_sync_delay[3];
include/net/bluetooth/hci.h: __u8 m_latency[3];
include/net/bluetooth/hci.h: __u8 s_latency[3];
I guess they all could benefit from having such a helper so we don't
have to resort in cpu_to_32 + memcpy.
> Regards
>
> Marcel
>
--
Luiz Augusto von Dentz
