[PATCH 1/2] drm/dp_mst: make functions that always return 0 return void.

[PATCH 1/2] drm/dp_mst: make functions that always return 0 return void.

[Dave Airlie]

This just drops the return and assigning it to a len variable
that never gets used.

Signed-off-by: Dave Airlie <airlied@redhat.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 29 ++++++++++-------------------
 1 file changed, 10 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index e23df5f..294d904 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -631,7 +631,7 @@ static bool drm_dp_sideband_parse_req(struct drm_dp_sideband_msg_rx *raw,
 	}
 }
 
-static int build_dpcd_write(struct drm_dp_sideband_msg_tx *msg, u8 port_num, u32 offset, u8 num_bytes, u8 *bytes)
+static void build_dpcd_write(struct drm_dp_sideband_msg_tx *msg, u8 port_num, u32 offset, u8 num_bytes, u8 *bytes)
 {
 	struct drm_dp_sideband_msg_req_body req;
 
@@ -641,20 +641,17 @@ static int build_dpcd_write(struct drm_dp_sideband_msg_tx *msg, u8 port_num, u32
 	req.u.dpcd_write.num_bytes = num_bytes;
 	req.u.dpcd_write.bytes = bytes;
 	drm_dp_encode_sideband_req(&req, msg);
-
-	return 0;
 }
 
-static int build_link_address(struct drm_dp_sideband_msg_tx *msg)
+static void build_link_address(struct drm_dp_sideband_msg_tx *msg)
 {
 	struct drm_dp_sideband_msg_req_body req;
 
 	req.req_type = DP_LINK_ADDRESS;
 	drm_dp_encode_sideband_req(&req, msg);
-	return 0;
 }
 
-static int build_enum_path_resources(struct drm_dp_sideband_msg_tx *msg, int port_num)
+static void build_enum_path_resources(struct drm_dp_sideband_msg_tx *msg, int port_num)
 {
 	struct drm_dp_sideband_msg_req_body req;
 
@@ -662,10 +659,9 @@ static int build_enum_path_resources(struct drm_dp_sideband_msg_tx *msg, int por
 	req.u.port_num.port_number = port_num;
 	drm_dp_encode_sideband_req(&req, msg);
 	msg->path_msg = true;
-	return 0;
 }
 
-static int build_allocate_payload(struct drm_dp_sideband_msg_tx *msg, int port_num,
+static void build_allocate_payload(struct drm_dp_sideband_msg_tx *msg, int port_num,
 				  u8 vcpi, uint16_t pbn)
 {
 	struct drm_dp_sideband_msg_req_body req;
@@ -676,7 +672,6 @@ static int build_allocate_payload(struct drm_dp_sideband_msg_tx *msg, int port_n
 	req.u.allocate_payload.pbn = pbn;
 	drm_dp_encode_sideband_req(&req, msg);
 	msg->path_msg = true;
-	return 0;
 }
 
 static int drm_dp_mst_assign_payload_id(struct drm_dp_mst_topology_mgr *mgr,
@@ -1461,7 +1456,6 @@ static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr,
 static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
 				    struct drm_dp_mst_branch *mstb)
 {
-	int len;
 	struct drm_dp_sideband_msg_tx *txmsg;
 	int ret;
 
@@ -1470,7 +1464,7 @@ static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
 		return -ENOMEM;
 
 	txmsg->dst = mstb;
-	len = build_link_address(txmsg);
+	build_link_address(txmsg);
 
 	drm_dp_queue_down_tx(mgr, txmsg);
 
@@ -1510,7 +1504,6 @@ static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
 					   struct drm_dp_mst_branch *mstb,
 					   struct drm_dp_mst_port *port)
 {
-	int len;
 	struct drm_dp_sideband_msg_tx *txmsg;
 	int ret;
 
@@ -1519,7 +1512,7 @@ static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
 		return -ENOMEM;
 
 	txmsg->dst = mstb;
-	len = build_enum_path_resources(txmsg, port->port_num);
+	build_enum_path_resources(txmsg, port->port_num);
 
 	drm_dp_queue_down_tx(mgr, txmsg);
 
@@ -1547,7 +1540,7 @@ static int drm_dp_payload_send_msg(struct drm_dp_mst_topology_mgr *mgr,
 {
 	struct drm_dp_sideband_msg_tx *txmsg;
 	struct drm_dp_mst_branch *mstb;
-	int len, ret;
+	int ret;
 
 	mstb = drm_dp_get_validated_mstb_ref(mgr, port->parent);
 	if (!mstb)
@@ -1560,9 +1553,8 @@ static int drm_dp_payload_send_msg(struct drm_dp_mst_topology_mgr *mgr,
 	}
 
 	txmsg->dst = mstb;
-	len = build_allocate_payload(txmsg, port->port_num,
-				     id,
-				     pbn);
+	build_allocate_payload(txmsg, port->port_num,
+			       id, pbn);
 
 	drm_dp_queue_down_tx(mgr, txmsg);
 
@@ -1772,7 +1764,6 @@ static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
 				  struct drm_dp_mst_port *port,
 				  int offset, int size, u8 *bytes)
 {
-	int len;
 	int ret;
 	struct drm_dp_sideband_msg_tx *txmsg;
 	struct drm_dp_mst_branch *mstb;
@@ -1787,7 +1778,7 @@ static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
 		goto fail_put;
 	}
 
-	len = build_dpcd_write(txmsg, port->port_num, offset, size, bytes);
+	build_dpcd_write(txmsg, port->port_num, offset, size, bytes);
 	txmsg->dst = mstb;
 
 	drm_dp_queue_down_tx(mgr, txmsg);
-- 
2.4.3

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[PATCH 2/2] drm/mst: update the link_address_sent before sending the link address (v2)

[Dave Airlie]

There is a race where the reply could get processed by another
work queue before we've updated the state.

Update the state before sending the msg to close it.

v2: reset value if return indicates we haven't send the msg.

Pointed out by Adam J Richter on

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91481
Signed-off-by: Dave Airlie <airlied@redhat.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 294d904..831096b9 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1101,8 +1101,10 @@ static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
 
 		ret = drm_dp_port_setup_pdt(port);
 		if (ret == true) {
-			drm_dp_send_link_address(mstb->mgr, port->mstb);
 			port->mstb->link_address_sent = true;
+			ret = drm_dp_send_link_address(mstb->mgr, port->mstb);
+			if (ret < 0)
+				port->mstb->link_address_sent = false;
 		}
 	}
 
@@ -1198,8 +1200,11 @@ static void drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *m
 	struct drm_dp_mst_port *port;
 	struct drm_dp_mst_branch *mstb_child;
 	if (!mstb->link_address_sent) {
-		drm_dp_send_link_address(mgr, mstb);
+		int ret;
 		mstb->link_address_sent = true;
+		ret = drm_dp_send_link_address(mgr, mstb);
+		if (ret < 0)
+			mstb->link_address_sent = false;
 	}
 	list_for_each_entry(port, &mstb->ports, next) {
 		if (port->input)
@@ -1493,11 +1498,12 @@ static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
 			}
 			(*mgr->cbs->hotplug)(mgr);
 		}
+		ret = 0;
 	} else
 		DRM_DEBUG_KMS("link address failed %d\n", ret);
 
 	kfree(txmsg);
-	return 0;
+	return ret;
 }
 
 static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
-- 
2.4.3

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Re: [PATCH 1/2] drm/dp_mst: make functions that always return 0 return void.

[Daniel Vetter]

On Sun, Sep 06, 2015 at 06:52:59PM +1000, Dave Airlie wrote:
> This just drops the return and assigning it to a len variable
> that never gets used.
> 
> Signed-off-by: Dave Airlie <airlied@redhat.com>

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 29 ++++++++++-------------------
>  1 file changed, 10 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index e23df5f..294d904 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -631,7 +631,7 @@ static bool drm_dp_sideband_parse_req(struct drm_dp_sideband_msg_rx *raw,
>  	}
>  }
>  
> -static int build_dpcd_write(struct drm_dp_sideband_msg_tx *msg, u8 port_num, u32 offset, u8 num_bytes, u8 *bytes)
> +static void build_dpcd_write(struct drm_dp_sideband_msg_tx *msg, u8 port_num, u32 offset, u8 num_bytes, u8 *bytes)
>  {
>  	struct drm_dp_sideband_msg_req_body req;
>  
> @@ -641,20 +641,17 @@ static int build_dpcd_write(struct drm_dp_sideband_msg_tx *msg, u8 port_num, u32
>  	req.u.dpcd_write.num_bytes = num_bytes;
>  	req.u.dpcd_write.bytes = bytes;
>  	drm_dp_encode_sideband_req(&req, msg);
> -
> -	return 0;
>  }
>  
> -static int build_link_address(struct drm_dp_sideband_msg_tx *msg)
> +static void build_link_address(struct drm_dp_sideband_msg_tx *msg)
>  {
>  	struct drm_dp_sideband_msg_req_body req;
>  
>  	req.req_type = DP_LINK_ADDRESS;
>  	drm_dp_encode_sideband_req(&req, msg);
> -	return 0;
>  }
>  
> -static int build_enum_path_resources(struct drm_dp_sideband_msg_tx *msg, int port_num)
> +static void build_enum_path_resources(struct drm_dp_sideband_msg_tx *msg, int port_num)
>  {
>  	struct drm_dp_sideband_msg_req_body req;
>  
> @@ -662,10 +659,9 @@ static int build_enum_path_resources(struct drm_dp_sideband_msg_tx *msg, int por
>  	req.u.port_num.port_number = port_num;
>  	drm_dp_encode_sideband_req(&req, msg);
>  	msg->path_msg = true;
> -	return 0;
>  }
>  
> -static int build_allocate_payload(struct drm_dp_sideband_msg_tx *msg, int port_num,
> +static void build_allocate_payload(struct drm_dp_sideband_msg_tx *msg, int port_num,
>  				  u8 vcpi, uint16_t pbn)
>  {
>  	struct drm_dp_sideband_msg_req_body req;
> @@ -676,7 +672,6 @@ static int build_allocate_payload(struct drm_dp_sideband_msg_tx *msg, int port_n
>  	req.u.allocate_payload.pbn = pbn;
>  	drm_dp_encode_sideband_req(&req, msg);
>  	msg->path_msg = true;
> -	return 0;
>  }
>  
>  static int drm_dp_mst_assign_payload_id(struct drm_dp_mst_topology_mgr *mgr,
> @@ -1461,7 +1456,6 @@ static void drm_dp_queue_down_tx(struct drm_dp_mst_topology_mgr *mgr,
>  static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
>  				    struct drm_dp_mst_branch *mstb)
>  {
> -	int len;
>  	struct drm_dp_sideband_msg_tx *txmsg;
>  	int ret;
>  
> @@ -1470,7 +1464,7 @@ static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
>  		return -ENOMEM;
>  
>  	txmsg->dst = mstb;
> -	len = build_link_address(txmsg);
> +	build_link_address(txmsg);
>  
>  	drm_dp_queue_down_tx(mgr, txmsg);
>  
> @@ -1510,7 +1504,6 @@ static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
>  					   struct drm_dp_mst_branch *mstb,
>  					   struct drm_dp_mst_port *port)
>  {
> -	int len;
>  	struct drm_dp_sideband_msg_tx *txmsg;
>  	int ret;
>  
> @@ -1519,7 +1512,7 @@ static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
>  		return -ENOMEM;
>  
>  	txmsg->dst = mstb;
> -	len = build_enum_path_resources(txmsg, port->port_num);
> +	build_enum_path_resources(txmsg, port->port_num);
>  
>  	drm_dp_queue_down_tx(mgr, txmsg);
>  
> @@ -1547,7 +1540,7 @@ static int drm_dp_payload_send_msg(struct drm_dp_mst_topology_mgr *mgr,
>  {
>  	struct drm_dp_sideband_msg_tx *txmsg;
>  	struct drm_dp_mst_branch *mstb;
> -	int len, ret;
> +	int ret;
>  
>  	mstb = drm_dp_get_validated_mstb_ref(mgr, port->parent);
>  	if (!mstb)
> @@ -1560,9 +1553,8 @@ static int drm_dp_payload_send_msg(struct drm_dp_mst_topology_mgr *mgr,
>  	}
>  
>  	txmsg->dst = mstb;
> -	len = build_allocate_payload(txmsg, port->port_num,
> -				     id,
> -				     pbn);
> +	build_allocate_payload(txmsg, port->port_num,
> +			       id, pbn);
>  
>  	drm_dp_queue_down_tx(mgr, txmsg);
>  
> @@ -1772,7 +1764,6 @@ static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
>  				  struct drm_dp_mst_port *port,
>  				  int offset, int size, u8 *bytes)
>  {
> -	int len;
>  	int ret;
>  	struct drm_dp_sideband_msg_tx *txmsg;
>  	struct drm_dp_mst_branch *mstb;
> @@ -1787,7 +1778,7 @@ static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
>  		goto fail_put;
>  	}
>  
> -	len = build_dpcd_write(txmsg, port->port_num, offset, size, bytes);
> +	build_dpcd_write(txmsg, port->port_num, offset, size, bytes);
>  	txmsg->dst = mstb;
>  
>  	drm_dp_queue_down_tx(mgr, txmsg);
> -- 
> 2.4.3
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH 2/2] drm/mst: update the link_address_sent before sending the link address (v2)

[Daniel Vetter]

On Sun, Sep 06, 2015 at 06:53:00PM +1000, Dave Airlie wrote:
> There is a race where the reply could get processed by another
> work queue before we've updated the state.
> 
> Update the state before sending the msg to close it.
> 
> v2: reset value if return indicates we haven't send the msg.
> 
> Pointed out by Adam J Richter on
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91481
> Signed-off-by: Dave Airlie <airlied@redhat.com>

Ok we see to have two callers of drm_dp_send_link_address:
- drm_dp_add_port, but the only caller of that in turn is again
  drm_dp_send_link_address. This is just self-recursion.
- drm_dp_check_and_send_link_address, which in turn is called only by
  itself and by drm_dp_mst_link_probe_work.

drm_dp_mst_link_probe_work is only called from the mgr->work function, and
a single work item is never run concurrently.

I don't see any race here at all. A good cleanup though would be what
Adam's original patch has done and move the link_address_sent = true into
drm_dp_send_link_address.

Cheers, Daniel

> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 294d904..831096b9 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -1101,8 +1101,10 @@ static void drm_dp_add_port(struct drm_dp_mst_branch *mstb,
>  
>  		ret = drm_dp_port_setup_pdt(port);
>  		if (ret == true) {
> -			drm_dp_send_link_address(mstb->mgr, port->mstb);
>  			port->mstb->link_address_sent = true;
> +			ret = drm_dp_send_link_address(mstb->mgr, port->mstb);
> +			if (ret < 0)
> +				port->mstb->link_address_sent = false;
>  		}
>  	}
>  
> @@ -1198,8 +1200,11 @@ static void drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *m
>  	struct drm_dp_mst_port *port;
>  	struct drm_dp_mst_branch *mstb_child;
>  	if (!mstb->link_address_sent) {
> -		drm_dp_send_link_address(mgr, mstb);
> +		int ret;
>  		mstb->link_address_sent = true;
> +		ret = drm_dp_send_link_address(mgr, mstb);
> +		if (ret < 0)
> +			mstb->link_address_sent = false;
>  	}
>  	list_for_each_entry(port, &mstb->ports, next) {
>  		if (port->input)
> @@ -1493,11 +1498,12 @@ static int drm_dp_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
>  			}
>  			(*mgr->cbs->hotplug)(mgr);
>  		}
> +		ret = 0;
>  	} else
>  		DRM_DEBUG_KMS("link address failed %d\n", ret);
>  
>  	kfree(txmsg);
> -	return 0;
> +	return ret;
>  }
>  
>  static int drm_dp_send_enum_path_resources(struct drm_dp_mst_topology_mgr *mgr,
> -- 
> 2.4.3
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
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Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH 2/2] drm/mst: update the link_address_sent before sending the link address (v2)

[Dave Airlie]

On 30 September 2015 at 17:44, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Sun, Sep 06, 2015 at 06:53:00PM +1000, Dave Airlie wrote:
>> There is a race where the reply could get processed by another
>> work queue before we've updated the state.
>>
>> Update the state before sending the msg to close it.
>>
>> v2: reset value if return indicates we haven't send the msg.
>>
>> Pointed out by Adam J Richter on
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91481
>> Signed-off-by: Dave Airlie <airlied@redhat.com>
>
> Ok we see to have two callers of drm_dp_send_link_address:
> - drm_dp_add_port, but the only caller of that in turn is again
>   drm_dp_send_link_address. This is just self-recursion.
> - drm_dp_check_and_send_link_address, which in turn is called only by
>   itself and by drm_dp_mst_link_probe_work.
>
> drm_dp_mst_link_probe_work is only called from the mgr->work function, and
> a single work item is never run concurrently.
>
> I don't see any race here at all. A good cleanup though would be what
> Adam's original patch has done and move the link_address_sent = true into
> drm_dp_send_link_address.

I think we were being paranoid about the work queue vs the send_link_address
if you can't have multiple then it matters not.

But I'll repost the cleaned up version as it makes things easier to grok.

Dave.
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