Subject: Re: [PATCH wpan-next 1/6] ieee802154: Add support for user scanning requests

From: Miquel Raynal <[email-masked]>
Date: Wed, 7 Dec 2022 14:44:57 +0100

Hi Alexander,

[email-masked] wrote on Wed, 7 Dec 2022 08:27:35 -0500:

> Hi,
> 
> On Mon, Dec 5, 2022 at 4:58 AM Miquel Raynal <[email-masked]> wrote:
> >
> > Hi Alexander,
> >
> > [email-masked] wrote on Sun, 4 Dec 2022 17:44:24 -0500:
> >  
> > > Hi,
> > >
> > > On Tue, Nov 29, 2022 at 11:02 AM Miquel Raynal
> > > <[email-masked]> wrote:  
> > > >
> > > > The ieee802154 layer should be able to scan a set of channels in order
> > > > to look for beacons advertizing PANs. Supporting this involves adding
> > > > two user commands: triggering scans and aborting scans. The user should
> > > > also be notified when a new beacon is received and also upon scan
> > > > termination.
> > > >
> > > > A scan request structure is created to list the requirements and to be
> > > > accessed asynchronously when changing channels or receiving beacons.
> > > >
> > > > Mac layers may now implement the ->trigger_scan() and ->abort_scan()
> > > > hooks.
> > > >
> > > > Co-developed-by: David Girault <[email-masked]>
> > > > Signed-off-by: David Girault <[email-masked]>
> > > > Signed-off-by: Miquel Raynal <[email-masked]>
> > > > ---
> > > >  include/linux/ieee802154.h |   3 +
> > > >  include/net/cfg802154.h    |  25 +++++
> > > >  include/net/nl802154.h     |  49 +++++++++
> > > >  net/ieee802154/nl802154.c  | 215 +++++++++++++++++++++++++++++++++++++
> > > >  net/ieee802154/nl802154.h  |   3 +
> > > >  net/ieee802154/rdev-ops.h  |  28 +++++
> > > >  net/ieee802154/trace.h     |  40 +++++++
> > > >  7 files changed, 363 insertions(+)
> > > >
> > > > diff --git a/include/linux/ieee802154.h b/include/linux/ieee802154.h
> > > > index 0303eb84d596..b22e4147d334 100644
> > > > --- a/include/linux/ieee802154.h
> > > > +++ b/include/linux/ieee802154.h
> > > > @@ -44,6 +44,9 @@
> > > >  #define IEEE802154_SHORT_ADDR_LEN      2
> > > >  #define IEEE802154_PAN_ID_LEN          2
> > > >
> > > > +/* Duration in superframe order */
> > > > +#define IEEE802154_MAX_SCAN_DURATION   14
> > > > +#define IEEE802154_ACTIVE_SCAN_DURATION        15
> > > >  #define IEEE802154_LIFS_PERIOD         40
> > > >  #define IEEE802154_SIFS_PERIOD         12
> > > >  #define IEEE802154_MAX_SIFS_FRAME_SIZE 18
> > > > diff --git a/include/net/cfg802154.h b/include/net/cfg802154.h
> > > > index d09c393d229f..76d4f95e9974 100644
> > > > --- a/include/net/cfg802154.h
> > > > +++ b/include/net/cfg802154.h
> > > > @@ -18,6 +18,7 @@
> > > >
> > > >  struct wpan_phy;
> > > >  struct wpan_phy_cca;
> > > > +struct cfg802154_scan_request;
> > > >
> > > >  #ifdef CONFIG_IEEE802154_NL802154_EXPERIMENTAL
> > > >  struct ieee802154_llsec_device_key;
> > > > @@ -67,6 +68,10 @@ struct cfg802154_ops {
> > > >                                 struct wpan_dev *wpan_dev, bool mode);
> > > >         int     (*set_ackreq_default)(struct wpan_phy *wpan_phy,
> > > >                                       struct wpan_dev *wpan_dev, bool ackreq);
> > > > +       int     (*trigger_scan)(struct wpan_phy *wpan_phy,
> > > > +                               struct cfg802154_scan_request *request);
> > > > +       int     (*abort_scan)(struct wpan_phy *wpan_phy,
> > > > +                             struct wpan_dev *wpan_dev);
> > > >  #ifdef CONFIG_IEEE802154_NL802154_EXPERIMENTAL
> > > >         void    (*get_llsec_table)(struct wpan_phy *wpan_phy,
> > > >                                    struct wpan_dev *wpan_dev,
> > > > @@ -278,6 +283,26 @@ struct ieee802154_coord_desc {
> > > >         bool gts_permit;
> > > >  };
> > > >
> > > > +/**
> > > > + * struct cfg802154_scan_request - Scan request
> > > > + *
> > > > + * @type: type of scan to be performed
> > > > + * @page: page on which to perform the scan
> > > > + * @channels: channels in te %page to be scanned
> > > > + * @duration: time spent on each channel, calculated with:
> > > > + *            aBaseSuperframeDuration * (2 ^ duration + 1)
> > > > + * @wpan_dev: the wpan device on which to perform the scan
> > > > + * @wpan_phy: the wpan phy on which to perform the scan
> > > > + */
> > > > +struct cfg802154_scan_request {
> > > > +       enum nl802154_scan_types type;
> > > > +       u8 page;
> > > > +       u32 channels;
> > > > +       u8 duration;
> > > > +       struct wpan_dev *wpan_dev;
> > > > +       struct wpan_phy *wpan_phy;
> > > > +};
> > > > +
> > > >  struct ieee802154_llsec_key_id {
> > > >         u8 mode;
> > > >         u8 id;
> > > > diff --git a/include/net/nl802154.h b/include/net/nl802154.h
> > > > index b79a89d5207c..79fbd820b25a 100644
> > > > --- a/include/net/nl802154.h
> > > > +++ b/include/net/nl802154.h
> > > > @@ -73,6 +73,9 @@ enum nl802154_commands {
> > > >         NL802154_CMD_DEL_SEC_LEVEL,
> > > >
> > > >         NL802154_CMD_SCAN_EVENT,
> > > > +       NL802154_CMD_TRIGGER_SCAN,
> > > > +       NL802154_CMD_ABORT_SCAN,
> > > > +       NL802154_CMD_SCAN_DONE,  
> > >
> > > Is NL802154_CMD_SCAN_DONE reserved now? I don't see it implemented in
> > > this series and I think we had some discussion about the need of abort
> > > vs done. Is the event now?  
> >
> > To be very honest I went back and forth about the "abort" information
> > so I don't remember exactly what was supposed to be implemented. The
> > current implementation forwards to userspace the reason (whether the
> > scan was finished or was aborted for an external reason). So it is
> > implemented this way:
> >  
> 
> I think it was also to implement a way to signal all listeners that
> there is such an operation ongoing? Do we have something like that?

When the kernel receives a CMD_TRIGGER_SCAN it starts the scan and if
everything is on track sends to the userspace listeners a
CMD_TRIGGER_SCAN in return, meaning "a scan has started".

So any listener would see:
CMD_TRIGGER_SCAN
SCAN_EVENT (+ content of the beacon)
...
SCAN_EVENT (+ content of the beacon)
CMD_SCAN_DONE (+ reason, see below)

> > * Patch 6/6 adds in mac802154/scan.c:
> >
> > +       cmd = aborted ? NL802154_CMD_ABORT_SCAN : NL802154_CMD_SCAN_DONE;
> > +       nl802154_scan_done(wpan_phy, wpan_dev, cmd);
> >
> > * And in patch 1/6, in ieee802154/nl802154.c:
> >
> > +static int nl802154_send_scan_msg(struct cfg802154_registered_device *rdev,
> > +                                 struct wpan_dev *wpan_dev, u8 cmd)
> > +{
> > [...]
> > +
> > +       ret = nl802154_prep_scan_msg(msg, rdev, wpan_dev, 0, 0, 0, cmd);
> >
> > Is this working for you?  
> 
> Sure this works in some way, I would put a reason parameter on DONE,
> but however...

Of course, I can do that. So NL802154_CMD_SCAN_DONE plus an u8
parameter:
NL802154_SCAN_DONE_REASON_FINISHED
NL802154_SCAN_DONE_REASON_ABORTED
?

Thanks,
Miquèl