On 3/12/2025 7:01 PM, Nithyanantham Paramasivam wrote:
> Currently, in NO_VIRTUAL_MONITOR mode, when creating an
> AP/STA + monitor, there is a restriction: if the AP/STA is running,
> setting the channel for the monitor is not allowed. For example,
> in a scenario with three supported radios where the AP uses only the
> 2 GHz and 5 GHz bands, the 6 GHz band remains available. However,
> due to the restriction that rdev->num_running_ifaces must equal
> rdev->num_running_monitor_ifaces in cfg80211_has_monitors_only(),
> we are unable to create the monitor interface.
>
> cfg80211_set_monitor_channel -> cfg80211_has_monitors_only()
>
> static inline bool cfg80211_has_monitors_only() {
> ...
> return rdev->num_running_ifaces == rdev->num_running_monitor_ifaces
> && rdev->num_running_ifaces > 0;
> }
>
> To address this issue, bypass the cfg80211_has_monitors_only() call
> for NO_VIRTUAL_MONITOR to allow monitor creation. In the mac80211
> layer, no additional changes are required. It follows the same
> sequence as standalone monitor creation in NO_VIRTUAL_MONITOR mode.
>
> Refer link to Felix's NO_VIRTUAL_MONITOR mode patch series.
> https://lore.kernel.org/linux-wireless/cover.bd168805c299851d01269473eb64e7b05edc41d6.1728372192.git-series.nbd@xxxxxxxx/
>
> Tested various scenarios with the cfg80211_has_monitors_only() bypass
> modification
>
> standalone monitor creation case
> ********************************
> 1. Create multiple standalone monitor interfaces with
> different radios
> - Allowed one channel per radio but multiple interfaces
> can be created with the same channel/radio.
>
> AP+Monitor case
> ***************
> 1. Create monitor interface with same channel used by AP
> - allowed
> 2. Create a monitor interface on a different channel (ch-6)
> on the same radio that the AP uses (ch-1) - not allowed
> 3. If the system supports three radios (2 GHz, 5 GHz, and 6 GHz)
> and the AP uses 5 GHz and 6 GHz - allowed to create a monitor on
> the 2 GHz radio
>
>
> Please share your thoughts on the following query
>
> In the virtual monitor mode design, only a single monitor interface
> per radio was supported and subsquent monitor creation shares the same
> vif. However, in NO_VIRTUAL_MONITOR mode(multi-wiphy scenario), there
> is no limitation on the number of interfaces that can be created (due
> to separate SDATA for each interface) and notified to the driver.
> For example, the ath driver can handle up to 16 interfaces per radio.
> Should we impose any limitations in cfg80211/mac80211 ?
>
> V2:
> - Rebased patches
> - Flag renamed to WIPHY_FLAG_SUPPORTS_CONCUR_MONITOR_N_OTHER_VIF
> - Patch(2/2) renamed
> - updated all the patch comments
>
> Nithyanantham Paramasivam (2):
> wifi: cfg80211: Allow monitor creation in NO_VIRTUAL_MONITOR mode with
> active AP
> wifi: mac80211: Set the WIPHY_FLAG_SUPPORTS_CONCUR_MONITOR_N_OTHER_VIF
> flag
>
> include/net/cfg80211.h | 55 ++++++++++++++++++++++--------------------
> net/mac80211/main.c | 4 +++
> net/wireless/chan.c | 4 ++-
> 3 files changed, 36 insertions(+), 27 deletions(-)
>
>
> base-commit: 42aa76e608ca845c98e79f9e23af0bdb07b2eb1d
Still looking for feedback on this series...
