[PATCH 51/55] staging: wfx: workaround bug with "iw scan"

Jérôme Pouiller
2019-12-16T17:07:06Z

mac80211 specification does not forbid hw_scan() to call
ieee80211_scan_completed(). However, from userspace point of view, not
all applications support this behavior. In particular, the code of iw
contains a big fat warning:

/*
* This code has a bug, which requires creating a separate
* nl80211 socket to fix:
* It is possible for a NL80211_CMD_NEW_SCAN_RESULTS or
* NL80211_CMD_SCAN_ABORTED message to be sent by the kernel
* before (!) we listen to it, because we only start listening
* after we send our scan request.
[...]
* Alas, the kernel doesn't do that (yet).
*/

So, we have to avoid to call ieee80211_scan_completed() from hw_scan()
(it's a kind of unwritten rule).

This patch relocates the hw_scan() process to a work_struct to fix the
problem.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
---
drivers/staging/wfx/scan.c | 47 ++++++++++++++++++++++++--------------
drivers/staging/wfx/scan.h | 1 +
drivers/staging/wfx/sta.c | 1 +
drivers/staging/wfx/wfx.h | 2 ++
4 files changed, 34 insertions(+), 17 deletions(-)

diff --git a/drivers/staging/wfx/scan.c b/drivers/staging/wfx/scan.c
index b73e61e8da46..540009b72240 100644
--- a/drivers/staging/wfx/scan.c
+++ b/drivers/staging/wfx/scan.c
@@ -71,23 +71,19 @@ static int send_scan_req(struct wfx_vif *wvif,
return i - start_idx;
}

-int wfx_hw_scan(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
- struct ieee80211_scan_request *hw_req)
+/*
+ * It is not really necessary to run scan request asynchronously. However,
+ * there is a bug in "iw scan" when ieee80211_scan_completed() is called before
+ * wfx_hw_scan() return
+ */
+void wfx_hw_scan_work(struct work_struct *work)
{
- struct wfx_dev *wdev = hw->priv;
- struct wfx_vif *wvif = (struct wfx_vif *) vif->drv_priv;
+ struct wfx_vif *wvif = container_of(work, struct wfx_vif, scan_work);
+ struct ieee80211_scan_request *hw_req = wvif->scan_req;
int chan_cur, ret;

- WARN_ON(hw_req->req.n_channels > HIF_API_MAX_NB_CHANNELS);
-
- if (vif->type == NL80211_IFTYPE_AP)
- return -EOPNOTSUPP;
-
- if (wvif->state == WFX_STATE_PRE_STA)
- return -EBUSY;
-
mutex_lock(&wvif->scan_lock);
- mutex_lock(&wdev->conf_mutex);
+ mutex_lock(&wvif->wdev->conf_mutex);
update_probe_tmpl(wvif, &hw_req->req);
wfx_fwd_probe_req(wvif, true);
chan_cur = 0;
@@ -96,18 +92,35 @@ int wfx_hw_scan(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
if (ret > 0)
chan_cur += ret;
} while (ret > 0 && chan_cur < hw_req->req.n_channels);
- __ieee80211_scan_completed_compat(hw, ret < 0);
- mutex_unlock(&wdev->conf_mutex);
+ mutex_unlock(&wvif->wdev->conf_mutex);
mutex_unlock(&wvif->scan_lock);
+ __ieee80211_scan_completed_compat(wvif->wdev->hw, ret < 0);
if (wvif->delayed_unjoin) {
wvif->delayed_unjoin = false;
- wfx_tx_lock(wdev);
+ wfx_tx_lock(wvif->wdev);
if (!schedule_work(&wvif->unjoin_work))
- wfx_tx_unlock(wdev);
+ wfx_tx_unlock(wvif->wdev);
} else if (wvif->delayed_link_loss) {
wvif->delayed_link_loss = false;
wfx_cqm_bssloss_sm(wvif, 1, 0, 0);
}
+}
+
+int wfx_hw_scan(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
+ struct ieee80211_scan_request *hw_req)
+{
+ struct wfx_vif *wvif = (struct wfx_vif *)vif->drv_priv;
+
+ WARN_ON(hw_req->req.n_channels > HIF_API_MAX_NB_CHANNELS);
+
+ if (vif->type == NL80211_IFTYPE_AP)
+ return -EOPNOTSUPP;
+
+ if (wvif->state == WFX_STATE_PRE_STA)
+ return -EBUSY;
+
+ wvif->scan_req = hw_req;
+ schedule_work(&wvif->scan_work);
return 0;
}

diff --git a/drivers/staging/wfx/scan.h b/drivers/staging/wfx/scan.h
index 03bc6c7e562d..b547f1927d72 100644
--- a/drivers/staging/wfx/scan.h
+++ b/drivers/staging/wfx/scan.h
@@ -15,6 +15,7 @@
struct wfx_dev;
struct wfx_vif;

+void wfx_hw_scan_work(struct work_struct *work);
int wfx_hw_scan(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
struct ieee80211_scan_request *req);
void wfx_scan_complete(struct wfx_vif *wvif,
diff --git a/drivers/staging/wfx/sta.c b/drivers/staging/wfx/sta.c
index 16f5db873275..4354bb8081c5 100644
--- a/drivers/staging/wfx/sta.c
+++ b/drivers/staging/wfx/sta.c
@@ -1427,6 +1427,7 @@ int wfx_add_interface(struct ieee80211_hw *hw, struct ieee80211_vif *vif)

mutex_init(&wvif->scan_lock);
init_completion(&wvif->scan_complete);
+ INIT_WORK(&wvif->scan_work, wfx_hw_scan_work);

mutex_unlock(&wdev->conf_mutex);

diff --git a/drivers/staging/wfx/wfx.h b/drivers/staging/wfx/wfx.h
index 3356d0cbf7af..b5f763c3fac7 100644
--- a/drivers/staging/wfx/wfx.h
+++ b/drivers/staging/wfx/wfx.h
@@ -127,7 +127,9 @@ struct wfx_vif {

/* avoid some operations in parallel with scan */
struct mutex scan_lock;
+ struct work_struct scan_work;
struct completion scan_complete;
+ struct ieee80211_scan_request *scan_req;

struct completion set_pm_mode_complete;

--
2.20.1