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Date:   Fri, 8 Apr 2022 18:21:02 -0400
From:   Jaehee Park <jhpark1013@gmail.com>
To:     Julia Lawall <julia.lawall@inria.fr>
Cc:     =?iso-8859-1?B?Suly9G1l?= Pouiller <jerome.pouiller@silabs.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org,
        outreachy@lists.linux.dev, Stefano Brivio <sbrivio@redhat.com>
Subject: Re: [PATCH] staging: wfx: use container_of() to get vif
Message-ID: <20220408222102.GB2511628@jaehee-ThinkPad-X1-Extreme>
References: <20220407204128.GA1810425@jaehee-ThinkPad-X1-Extreme>
 <alpine.DEB.2.22.394.2204081149360.2196@hadrien>
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On Fri, Apr 08, 2022 at 11:49:49AM +0200, Julia Lawall wrote:
> 
> 
> On Thu, 7 Apr 2022, Jaehee Park wrote:
> 
> > Use container_of() to get vif. This improves the code in two ways:
> > [1] it speeds up the compilation because container_of() saves steps to
> > retrieve vif (the representation of ieee80211_vif), and
> 
> I don't understand this part.
> 
> julia
> 

Thank you for your message. I revised the commit message (below)-- 
I hope it makes it clearer. I'm open to suggestions as well!

Currently, upon virtual interface creation, wfx_add_interface() stores 
a reference to the corresponding struct ieee80211_vif in private data, 
for later usage. This is not needed when using the container_of 
construct. This construct already has all the info it needs to retrieve
the reference to the corresponding struct from the offset that is 
already available, inherent in container_of(), between its type and 
member inputs (struct ieee80211_vif and drv_priv, respectively). 
Remove vif (which was previously storing the reference to the struct 
ieee80211_vif) from the struct wfx_vif, define a macro 
wvif_to_vif(wvif) for container_of(), and replace all wvif->vif with 
the newly defined container_of construct.

Sorry if I'm putting out more information than was asked for:
Diagram is worth a thousand words; this one is made by Stefano when 
he was explaining the container_of() construct:

.-----------------------------------.
|  .------------------------------. |
'->| struct ieee80211_vif         | |
   |------------------------------| |
   | 1                            | |
   | 2                            | |
   |  .--------------------------.| |
   | 3| struct wfx_vif drv_priv   | |
   |  |---------------------------| |
   |  | ...                       | |
   |  |                           | |
   |  | struct ieee80211_vif *vif---'
   '------------------------------'
In this example, the offset is 3.
What I want to convey here is the compiler already knows the offset
of drv_priv within struct ieee80211_vif by using the container_of() 
construct. So, it doesn't need to do extra work.

> > [2] it eliminates the need to define multiple pointers. Previously,
> > after setting the pointer to drv_priv, another pointer had to be
> > defined by vif in struct wfx_vif to point back to ieee80211_vif.
> > Remove vif from the struct wfx_vif, define a macro wvif_to_vif(ptr)
> > for container_of(), and replace all wvif->vif with the newly defined
> > container_of() construct.
> >
> > Signed-off-by: Jaehee Park <jhpark1013@gmail.com>
> > ---
> > Questions:
> > - These changes built for me, but it would be great if someone can test it on the actual hardware.
> > - We noticed that the?development of the wfx driver is happening in netdev instead of the staging directory. Do you suggest that I use the net-next tree for this change?
> > ?
> >  drivers/staging/wfx/data_rx.c |  4 ++--
> >  drivers/staging/wfx/data_tx.c |  2 +-
> >  drivers/staging/wfx/key.c     |  3 +--
> >  drivers/staging/wfx/queue.c   |  2 +-
> >  drivers/staging/wfx/scan.c    |  6 ++---
> >  drivers/staging/wfx/sta.c     | 45 ++++++++++++++++-------------------
> >  drivers/staging/wfx/wfx.h     |  3 ++-
> >  7 files changed, 31 insertions(+), 34 deletions(-)
> >
> > diff --git a/drivers/staging/wfx/data_rx.c b/drivers/staging/wfx/data_rx.c
> > index a4b5ffe158e4..98c2223089b8 100644
> > --- a/drivers/staging/wfx/data_rx.c
> > +++ b/drivers/staging/wfx/data_rx.c
> > @@ -24,12 +24,12 @@ static void wfx_rx_handle_ba(struct wfx_vif *wvif, struct ieee80211_mgmt *mgmt)
> >  	case WLAN_ACTION_ADDBA_REQ:
> >  		params = le16_to_cpu(mgmt->u.action.u.addba_req.capab);
> >  		tid = (params & IEEE80211_ADDBA_PARAM_TID_MASK) >> 2;
> > -		ieee80211_start_rx_ba_session_offl(wvif->vif, mgmt->sa, tid);
> > +		ieee80211_start_rx_ba_session_offl(wvif_to_vif(wvif), mgmt->sa, tid);
> >  		break;
> >  	case WLAN_ACTION_DELBA:
> >  		params = le16_to_cpu(mgmt->u.action.u.delba.params);
> >  		tid = (params &  IEEE80211_DELBA_PARAM_TID_MASK) >> 12;
> > -		ieee80211_stop_rx_ba_session_offl(wvif->vif, mgmt->sa, tid);
> > +		ieee80211_stop_rx_ba_session_offl(wvif_to_vif(wvif), mgmt->sa, tid);
> >  		break;
> >  	}
> >  }
> > diff --git a/drivers/staging/wfx/data_tx.c b/drivers/staging/wfx/data_tx.c
> > index e07381b2ff4d..fd79e03a08c5 100644
> > --- a/drivers/staging/wfx/data_tx.c
> > +++ b/drivers/staging/wfx/data_tx.c
> > @@ -216,7 +216,7 @@ static u8 wfx_tx_get_link_id(struct wfx_vif *wvif, struct ieee80211_sta *sta,
> >
> >  	if (sta_priv && sta_priv->link_id)
> >  		return sta_priv->link_id;
> > -	if (wvif->vif->type != NL80211_IFTYPE_AP)
> > +	if (wvif_to_vif(wvif)->type != NL80211_IFTYPE_AP)
> >  		return 0;
> >  	if (is_multicast_ether_addr(da))
> >  		return 0;
> > diff --git a/drivers/staging/wfx/key.c b/drivers/staging/wfx/key.c
> > index 8f23e8d42bd4..71b1fca70248 100644
> > --- a/drivers/staging/wfx/key.c
> > +++ b/drivers/staging/wfx/key.c
> > @@ -174,7 +174,7 @@ static int wfx_add_key(struct wfx_vif *wvif, struct ieee80211_sta *sta,
> >  			k.type = fill_tkip_pair(&k.key.tkip_pairwise_key, key, sta->addr);
> >  		else
> >  			k.type = fill_tkip_group(&k.key.tkip_group_key, key, &seq,
> > -						 wvif->vif->type);
> > +						 wvif_to_vif(wvif)->type);
> >  	} else if (key->cipher == WLAN_CIPHER_SUITE_CCMP) {
> >  		if (pairwise)
> >  			k.type = fill_ccmp_pair(&k.key.aes_pairwise_key, key, sta->addr);
> > @@ -224,4 +224,3 @@ int wfx_set_key(struct ieee80211_hw *hw, enum set_key_cmd cmd, struct ieee80211_
> >  	mutex_unlock(&wvif->wdev->conf_mutex);
> >  	return ret;
> >  }
> > -
> > diff --git a/drivers/staging/wfx/queue.c b/drivers/staging/wfx/queue.c
> > index 729825230db2..a2745d1024c6 100644
> > --- a/drivers/staging/wfx/queue.c
> > +++ b/drivers/staging/wfx/queue.c
> > @@ -207,7 +207,7 @@ bool wfx_tx_queues_has_cab(struct wfx_vif *wvif)
> >  {
> >  	int i;
> >
> > -	if (wvif->vif->type != NL80211_IFTYPE_AP)
> > +	if (wvif_to_vif(wvif)->type != NL80211_IFTYPE_AP)
> >  		return false;
> >  	for (i = 0; i < IEEE80211_NUM_ACS; ++i)
> >  		/* Note: since only AP can have mcast frames in queue and only one vif can be AP,
> > diff --git a/drivers/staging/wfx/scan.c b/drivers/staging/wfx/scan.c
> > index 7f34f0d322f9..5c25fde3fc41 100644
> > --- a/drivers/staging/wfx/scan.c
> > +++ b/drivers/staging/wfx/scan.c
> > @@ -25,7 +25,7 @@ static int update_probe_tmpl(struct wfx_vif *wvif, struct cfg80211_scan_request
> >  {
> >  	struct sk_buff *skb;
> >
> > -	skb = ieee80211_probereq_get(wvif->wdev->hw, wvif->vif->addr, NULL, 0, req->ie_len);
> > +	skb = ieee80211_probereq_get(wvif->wdev->hw, wvif_to_vif(wvif)->addr, NULL, 0, req->ie_len);
> >  	if (!skb)
> >  		return -ENOMEM;
> >
> > @@ -75,8 +75,8 @@ static int send_scan_req(struct wfx_vif *wvif, struct cfg80211_scan_request *req
> >  	} else {
> >  		ret = wvif->scan_nb_chan_done;
> >  	}
> > -	if (req->channels[start_idx]->max_power != wvif->vif->bss_conf.txpower)
> > -		wfx_hif_set_output_power(wvif, wvif->vif->bss_conf.txpower);
> > +	if (req->channels[start_idx]->max_power != wvif_to_vif(wvif)->bss_conf.txpower)
> > +		wfx_hif_set_output_power(wvif, wvif_to_vif(wvif)->bss_conf.txpower);
> >  	wfx_tx_unlock(wvif->wdev);
> >  	return ret;
> >  }
> > diff --git a/drivers/staging/wfx/sta.c b/drivers/staging/wfx/sta.c
> > index 03025ef7f1be..b634c8e004db 100644
> > --- a/drivers/staging/wfx/sta.c
> > +++ b/drivers/staging/wfx/sta.c
> > @@ -132,7 +132,7 @@ void wfx_configure_filter(struct ieee80211_hw *hw, unsigned int changed_flags,
> >  			filter_bssid = true;
> >
> >  		/* In AP mode, chip can reply to probe request itself */
> > -		if (*total_flags & FIF_PROBE_REQ && wvif->vif->type == NL80211_IFTYPE_AP) {
> > +		if (*total_flags & FIF_PROBE_REQ && wvif_to_vif(wvif)->type == NL80211_IFTYPE_AP) {
> >  			dev_dbg(wdev->dev, "do not forward probe request in AP mode\n");
> >  			*total_flags &= ~FIF_PROBE_REQ;
> >  		}
> > @@ -153,18 +153,18 @@ static int wfx_get_ps_timeout(struct wfx_vif *wvif, bool *enable_ps)
> >  	struct ieee80211_channel *chan0 = NULL, *chan1 = NULL;
> >  	struct ieee80211_conf *conf = &wvif->wdev->hw->conf;
> >
> > -	WARN(!wvif->vif->bss_conf.assoc && enable_ps,
> > +	WARN(!wvif_to_vif(wvif)->bss_conf.assoc && enable_ps,
> >  	     "enable_ps is reliable only if associated");
> >  	if (wdev_to_wvif(wvif->wdev, 0))
> > -		chan0 = wdev_to_wvif(wvif->wdev, 0)->vif->bss_conf.chandef.chan;
> > +		chan0 = wvif_to_vif(wdev_to_wvif(wvif->wdev, 0))->bss_conf.chandef.chan;
> >  	if (wdev_to_wvif(wvif->wdev, 1))
> > -		chan1 = wdev_to_wvif(wvif->wdev, 1)->vif->bss_conf.chandef.chan;
> > -	if (chan0 && chan1 && wvif->vif->type != NL80211_IFTYPE_AP) {
> > +		chan1 = wvif_to_vif(wdev_to_wvif(wvif->wdev, 1))->bss_conf.chandef.chan;
> > +	if (chan0 && chan1 && wvif_to_vif(wvif)->type != NL80211_IFTYPE_AP) {
> >  		if (chan0->hw_value == chan1->hw_value) {
> >  			/* It is useless to enable PS if channels are the same. */
> >  			if (enable_ps)
> >  				*enable_ps = false;
> > -			if (wvif->vif->bss_conf.assoc && wvif->vif->bss_conf.ps)
> > +			if (wvif_to_vif(wvif)->bss_conf.assoc && wvif_to_vif(wvif)->bss_conf.ps)
> >  				dev_info(wvif->wdev->dev, "ignoring requested PS mode");
> >  			return -1;
> >  		}
> > @@ -177,8 +177,8 @@ static int wfx_get_ps_timeout(struct wfx_vif *wvif, bool *enable_ps)
> >  			return 30;
> >  	}
> >  	if (enable_ps)
> > -		*enable_ps = wvif->vif->bss_conf.ps;
> > -	if (wvif->vif->bss_conf.assoc && wvif->vif->bss_conf.ps)
> > +		*enable_ps = wvif_to_vif(wvif)->bss_conf.ps;
> > +	if (wvif_to_vif(wvif)->bss_conf.assoc && wvif_to_vif(wvif)->bss_conf.ps)
> >  		return conf->dynamic_ps_timeout;
> >  	else
> >  		return -1;
> > @@ -189,7 +189,7 @@ int wfx_update_pm(struct wfx_vif *wvif)
> >  	int ps_timeout;
> >  	bool ps;
> >
> > -	if (!wvif->vif->bss_conf.assoc)
> > +	if (!wvif_to_vif(wvif)->bss_conf.assoc)
> >  		return 0;
> >  	ps_timeout = wfx_get_ps_timeout(wvif, &ps);
> >  	if (!ps)
> > @@ -215,7 +215,7 @@ int wfx_conf_tx(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
> >  	mutex_lock(&wdev->conf_mutex);
> >  	assign_bit(queue, &wvif->uapsd_mask, params->uapsd);
> >  	wfx_hif_set_edca_queue_params(wvif, queue, params);
> > -	if (wvif->vif->type == NL80211_IFTYPE_STATION && old_uapsd != wvif->uapsd_mask) {
> > +	if (wvif_to_vif(wvif)->type == NL80211_IFTYPE_STATION && old_uapsd != wvif->uapsd_mask) {
> >  		wfx_hif_set_uapsd_info(wvif, wvif->uapsd_mask);
> >  		wfx_update_pm(wvif);
> >  	}
> > @@ -242,20 +242,20 @@ void wfx_event_report_rssi(struct wfx_vif *wvif, u8 raw_rcpi_rssi)
> >  	int cqm_evt;
> >
> >  	rcpi_rssi = raw_rcpi_rssi / 2 - 110;
> > -	if (rcpi_rssi <= wvif->vif->bss_conf.cqm_rssi_thold)
> > +	if (rcpi_rssi <= wvif_to_vif(wvif)->bss_conf.cqm_rssi_thold)
> >  		cqm_evt = NL80211_CQM_RSSI_THRESHOLD_EVENT_LOW;
> >  	else
> >  		cqm_evt = NL80211_CQM_RSSI_THRESHOLD_EVENT_HIGH;
> > -	ieee80211_cqm_rssi_notify(wvif->vif, cqm_evt, rcpi_rssi, GFP_KERNEL);
> > +	ieee80211_cqm_rssi_notify(wvif_to_vif(wvif), cqm_evt, rcpi_rssi, GFP_KERNEL);
> >  }
> >
> >  static void wfx_beacon_loss_work(struct work_struct *work)
> >  {
> >  	struct wfx_vif *wvif = container_of(to_delayed_work(work), struct wfx_vif,
> >  					    beacon_loss_work);
> > -	struct ieee80211_bss_conf *bss_conf = &wvif->vif->bss_conf;
> > +	struct ieee80211_bss_conf *bss_conf = &wvif_to_vif(wvif)->bss_conf;
> >
> > -	ieee80211_beacon_loss(wvif->vif);
> > +	ieee80211_beacon_loss(wvif_to_vif(wvif));
> >  	schedule_delayed_work(to_delayed_work(work), msecs_to_jiffies(bss_conf->beacon_int));
> >  }
> >
> > @@ -323,13 +323,13 @@ static int wfx_upload_ap_templates(struct wfx_vif *wvif)
> >  {
> >  	struct sk_buff *skb;
> >
> > -	skb = ieee80211_beacon_get(wvif->wdev->hw, wvif->vif);
> > +	skb = ieee80211_beacon_get(wvif->wdev->hw, wvif_to_vif(wvif));
> >  	if (!skb)
> >  		return -ENOMEM;
> >  	wfx_hif_set_template_frame(wvif, skb, HIF_TMPLT_BCN, API_RATE_INDEX_B_1MBPS);
> >  	dev_kfree_skb(skb);
> >
> > -	skb = ieee80211_proberesp_get(wvif->wdev->hw, wvif->vif);
> > +	skb = ieee80211_proberesp_get(wvif->wdev->hw, wvif_to_vif(wvif));
> >  	if (!skb)
> >  		return -ENOMEM;
> >  	wfx_hif_set_template_frame(wvif, skb, HIF_TMPLT_PRBRES, API_RATE_INDEX_B_1MBPS);
> > @@ -339,7 +339,7 @@ static int wfx_upload_ap_templates(struct wfx_vif *wvif)
> >
> >  static void wfx_set_mfp_ap(struct wfx_vif *wvif)
> >  {
> > -	struct sk_buff *skb = ieee80211_beacon_get(wvif->wdev->hw, wvif->vif);
> > +	struct sk_buff *skb = ieee80211_beacon_get(wvif->wdev->hw, wvif_to_vif(wvif));
> >  	const int ieoffset = offsetof(struct ieee80211_mgmt, u.beacon.variable);
> >  	const u16 *ptr = (u16 *)cfg80211_find_ie(WLAN_EID_RSN, skb->data + ieoffset,
> >  						 skb->len - ieoffset);
> > @@ -389,7 +389,7 @@ void wfx_stop_ap(struct ieee80211_hw *hw, struct ieee80211_vif *vif)
> >  static void wfx_join(struct wfx_vif *wvif)
> >  {
> >  	int ret;
> > -	struct ieee80211_bss_conf *conf = &wvif->vif->bss_conf;
> > +	struct ieee80211_bss_conf *conf = &wvif_to_vif(wvif)->bss_conf;
> >  	struct cfg80211_bss *bss = NULL;
> >  	u8 ssid[IEEE80211_MAX_SSID_LEN];
> >  	const u8 *ssid_ie = NULL;
> > @@ -420,7 +420,7 @@ static void wfx_join(struct wfx_vif *wvif)
> >  	wvif->join_in_progress = true;
> >  	ret = wfx_hif_join(wvif, conf, wvif->channel, ssid, ssid_len);
> >  	if (ret) {
> > -		ieee80211_connection_loss(wvif->vif);
> > +		ieee80211_connection_loss(wvif_to_vif(wvif));
> >  		wfx_reset(wvif);
> >  	} else {
> >  		/* Due to beacon filtering it is possible that the AP's beacon is not known for the
> > @@ -440,7 +440,7 @@ static void wfx_join_finalize(struct wfx_vif *wvif, struct ieee80211_bss_conf *i
> >
> >  	rcu_read_lock(); /* protect sta */
> >  	if (info->bssid && !info->ibss_joined)
> > -		sta = ieee80211_find_sta(wvif->vif, info->bssid);
> > +		sta = ieee80211_find_sta(wvif_to_vif(wvif), info->bssid);
> >  	if (sta && sta->ht_cap.ht_supported)
> >  		ampdu_density = sta->ht_cap.ampdu_density;
> >  	if (sta && sta->ht_cap.ht_supported &&
> > @@ -565,7 +565,7 @@ static int wfx_update_tim(struct wfx_vif *wvif)
> >  	u16 tim_offset, tim_length;
> >  	u8 *tim_ptr;
> >
> > -	skb = ieee80211_beacon_get_tim(wvif->wdev->hw, wvif->vif, &tim_offset, &tim_length);
> > +	skb = ieee80211_beacon_get_tim(wvif->wdev->hw, wvif_to_vif(wvif), &tim_offset, &tim_length);
> >  	if (!skb)
> >  		return -ENOENT;
> >  	tim_ptr = skb->data + tim_offset;
> > @@ -707,8 +707,6 @@ int wfx_add_interface(struct ieee80211_hw *hw, struct ieee80211_vif *vif)
> >  		return -EOPNOTSUPP;
> >  	}
> >
> > -	/* FIXME: prefer use of container_of() to get vif */
> > -	wvif->vif = vif;
> >  	wvif->wdev = wdev;
> >
> >  	wvif->link_id_map = 1; /* link-id 0 is reserved for multicast */
> > @@ -767,7 +765,6 @@ void wfx_remove_interface(struct ieee80211_hw *hw, struct ieee80211_vif *vif)
> >
> >  	cancel_delayed_work_sync(&wvif->beacon_loss_work);
> >  	wdev->vif[wvif->id] = NULL;
> > -	wvif->vif = NULL;
> >
> >  	mutex_unlock(&wdev->conf_mutex);
> >
> > diff --git a/drivers/staging/wfx/wfx.h b/drivers/staging/wfx/wfx.h
> > index 6594cc647c2f..78f2a416fe4f 100644
> > --- a/drivers/staging/wfx/wfx.h
> > +++ b/drivers/staging/wfx/wfx.h
> > @@ -25,6 +25,8 @@
> >  #define USEC_PER_TXOP 32 /* see struct ieee80211_tx_queue_params */
> >  #define USEC_PER_TU 1024
> >
> > +#define wvif_to_vif(ptr)(container_of((void *)ptr, struct ieee80211_vif, drv_priv))
> > +
> >  struct wfx_hwbus_ops;
> >
> >  struct wfx_dev {
> > @@ -61,7 +63,6 @@ struct wfx_dev {
> >
> >  struct wfx_vif {
> >  	struct wfx_dev             *wdev;
> > -	struct ieee80211_vif       *vif;
> >  	struct ieee80211_channel   *channel;
> >  	int                        id;
> >
> > --
> > 2.25.1
> >
> >
> >