Re: [PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors

Re: [PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors

[kernel test robot]

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
In-Reply-To: <20231222043308.3090089-9-airlied@gmail.com>
References: <20231222043308.3090089-9-airlied@gmail.com>
TO: Dave Airlie <airlied@gmail.com>
TO: dri-devel@lists.freedesktop.org
TO: nouveau@lists.freedesktop.org

Hi Dave,

kernel test robot noticed the following build warnings:

[auto build test WARNING on drm-misc/drm-misc-next]
[also build test WARNING on drm/drm-next drm-exynos/exynos-drm-next drm-intel/for-linux-next-fixes drm-tip/drm-tip linus/master v6.7-rc7 next-20231220]
[cannot apply to drm-intel/for-linux-next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Dave-Airlie/nouveau-gsp-drop-some-acpi-related-debug/20231222-180432
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20231222043308.3090089-9-airlied%40gmail.com
patch subject: [PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors
:::::: branch date: 5 days ago
:::::: commit date: 5 days ago
config: powerpc-randconfig-r071-20231226 (https://download.01.org/0day-ci/archive/20231227/202312271917.55xuDMdc-lkp@intel.com/config)
compiler: clang version 18.0.0git (https://github.com/llvm/llvm-project d3ef86708241a3bee902615c190dead1638c4e09)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202312271917.55xuDMdc-lkp@intel.com/

New smatch warnings:
drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:659 r535_gsp_rpc_rm_ctrl_push() warn: passing zero to 'PTR_ERR'
drivers/gpu/drm/nouveau/nvkm/engine/disp/r535.c:1063 r535_dp_aux_xfer() warn: passing a valid pointer to 'PTR_ERR'

Old smatch warnings:
drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1887 nvkm_gsp_radix3_sg() error: uninitialized symbol 'addr'.

vim +/PTR_ERR +659 drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c

4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  648  
af265ee961627a Dave Airlie 2023-12-22  649  static int
af265ee961627a Dave Airlie 2023-12-22  650  r535_gsp_rpc_rm_ctrl_push(struct nvkm_gsp_object *object, void **argv, u32 repc)
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  651  {
af265ee961627a Dave Airlie 2023-12-22  652  	rpc_gsp_rm_control_v03_00 *rpc = container_of((*argv), typeof(*rpc), params);
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  653  	struct nvkm_gsp *gsp = object->client->gsp;
af265ee961627a Dave Airlie 2023-12-22  654  	int ret = 0;
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  655  
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  656  	rpc = nvkm_gsp_rpc_push(gsp, rpc, true, repc);
af265ee961627a Dave Airlie 2023-12-22  657  	if (IS_ERR_OR_NULL(rpc)) {
af265ee961627a Dave Airlie 2023-12-22  658  		*argv = NULL;
af265ee961627a Dave Airlie 2023-12-22 @659  		return PTR_ERR(rpc);
af265ee961627a Dave Airlie 2023-12-22  660  	}
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  661  
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  662  	if (rpc->status) {
af265ee961627a Dave Airlie 2023-12-22  663  		ret = r535_rpc_status_to_errno(rpc->status);
555bb9c29a45be Dave Airlie 2023-12-22  664  		if (ret != -EAGAIN)
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  665  			nvkm_error(&gsp->subdev, "cli:0x%08x obj:0x%08x ctrl cmd:0x%08x failed: 0x%08x\n",
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  666  				   object->client->object.handle, object->handle, rpc->cmd, rpc->status);
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  667  	}
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  668  
af265ee961627a Dave Airlie 2023-12-22  669  	if (repc)
af265ee961627a Dave Airlie 2023-12-22  670  		*argv = rpc->params;
af265ee961627a Dave Airlie 2023-12-22  671  	else
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  672  		nvkm_gsp_rpc_done(gsp, rpc);
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  673  
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  674  	return ret;
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  675  }
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  676  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

nouveau GSP fixes

[Dave Airlie]

This is a collection of nouveau debug prints, memory leak, a very
annoying race condition causing system hangs with prime scenarios,
and a fix from Lyude to get the panel on my laptop working.

I'd like to get these into 6.7,

Dave.

[PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors

[Dave Airlie]

It looks like for some messages the upper layers need to get access to the
results of the message so we can interpret it.

Rework the ctrl push interface to not free things and cleanup properly
whereever it errors out.

Requested-by: Lyude
Signed-off-by: Dave Airlie <airlied@redhat.com>
---
 .../gpu/drm/nouveau/include/nvkm/subdev/gsp.h |  17 +--
 .../gpu/drm/nouveau/nvkm/engine/disp/r535.c   | 108 +++++++++++-------
 .../gpu/drm/nouveau/nvkm/subdev/gsp/r535.c    |  36 +++---
 3 files changed, 100 insertions(+), 61 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/include/nvkm/subdev/gsp.h b/drivers/gpu/drm/nouveau/include/nvkm/subdev/gsp.h
index 2fa0445d8928..d1437c08645f 100644
--- a/drivers/gpu/drm/nouveau/include/nvkm/subdev/gsp.h
+++ b/drivers/gpu/drm/nouveau/include/nvkm/subdev/gsp.h
@@ -187,7 +187,7 @@ struct nvkm_gsp {
 		void (*rpc_done)(struct nvkm_gsp *gsp, void *repv);
 
 		void *(*rm_ctrl_get)(struct nvkm_gsp_object *, u32 cmd, u32 argc);
-		void *(*rm_ctrl_push)(struct nvkm_gsp_object *, void *argv, u32 repc);
+		int (*rm_ctrl_push)(struct nvkm_gsp_object *, void **argv, u32 repc);
 		void (*rm_ctrl_done)(struct nvkm_gsp_object *, void *repv);
 
 		void *(*rm_alloc_get)(struct nvkm_gsp_object *, u32 oclass, u32 argc);
@@ -265,7 +265,7 @@ nvkm_gsp_rm_ctrl_get(struct nvkm_gsp_object *object, u32 cmd, u32 argc)
 	return object->client->gsp->rm->rm_ctrl_get(object, cmd, argc);
 }
 
-static inline void *
+static inline int
 nvkm_gsp_rm_ctrl_push(struct nvkm_gsp_object *object, void *argv, u32 repc)
 {
 	return object->client->gsp->rm->rm_ctrl_push(object, argv, repc);
@@ -275,21 +275,24 @@ static inline void *
 nvkm_gsp_rm_ctrl_rd(struct nvkm_gsp_object *object, u32 cmd, u32 repc)
 {
 	void *argv = nvkm_gsp_rm_ctrl_get(object, cmd, repc);
+	int ret;
 
 	if (IS_ERR(argv))
 		return argv;
 
-	return nvkm_gsp_rm_ctrl_push(object, argv, repc);
+	ret = nvkm_gsp_rm_ctrl_push(object, &argv, repc);
+	if (ret)
+		return ERR_PTR(ret);
+	return argv;
 }
 
 static inline int
 nvkm_gsp_rm_ctrl_wr(struct nvkm_gsp_object *object, void *argv)
 {
-	void *repv = nvkm_gsp_rm_ctrl_push(object, argv, 0);
-
-	if (IS_ERR(repv))
-		return PTR_ERR(repv);
+	int ret = nvkm_gsp_rm_ctrl_push(object, &argv, 0);
 
+	if (ret)
+		return ret;
 	return 0;
 }
 
diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/disp/r535.c b/drivers/gpu/drm/nouveau/nvkm/engine/disp/r535.c
index 1c8c4cca0957..1b4f988df7ed 100644
--- a/drivers/gpu/drm/nouveau/nvkm/engine/disp/r535.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/disp/r535.c
@@ -282,7 +282,7 @@ r535_sor_bl_get(struct nvkm_ior *sor)
 {
 	struct nvkm_disp *disp = sor->disp;
 	NV0073_CTRL_SPECIFIC_BACKLIGHT_BRIGHTNESS_PARAMS *ctrl;
-	int lvl;
+	int ret, lvl;
 
 	ctrl = nvkm_gsp_rm_ctrl_get(&disp->rm.objcom,
 				    NV0073_CTRL_CMD_SPECIFIC_GET_BACKLIGHT_BRIGHTNESS,
@@ -292,9 +292,11 @@ r535_sor_bl_get(struct nvkm_ior *sor)
 
 	ctrl->displayId = BIT(sor->asy.outp->index);
 
-	ctrl = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, ctrl, sizeof(*ctrl));
-	if (IS_ERR(ctrl))
-		return PTR_ERR(ctrl);
+	ret = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, &ctrl, sizeof(*ctrl));
+	if (ret) {
+		nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
+		return ret;
+	}
 
 	lvl = ctrl->brightness;
 	nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
@@ -649,9 +651,11 @@ r535_conn_new(struct nvkm_disp *disp, u32 id)
 	ctrl->subDeviceInstance = 0;
 	ctrl->displayId = BIT(id);
 
-	ctrl = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, ctrl, sizeof(*ctrl));
-	if (IS_ERR(ctrl))
-		return (void *)ctrl;
+	ret = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, &ctrl, sizeof(*ctrl));
+	if (ret) {
+		nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
+		return ERR_PTR(ret);
+	}
 
 	list_for_each_entry(conn, &disp->conns, head) {
 		if (conn->index == ctrl->data[0].index) {
@@ -686,7 +690,7 @@ r535_outp_acquire(struct nvkm_outp *outp, bool hda)
 	struct nvkm_disp *disp = outp->disp;
 	struct nvkm_ior *ior;
 	NV0073_CTRL_DFP_ASSIGN_SOR_PARAMS *ctrl;
-	int or;
+	int ret, or;
 
 	ctrl = nvkm_gsp_rm_ctrl_get(&disp->rm.objcom,
 				    NV0073_CTRL_CMD_DFP_ASSIGN_SOR, sizeof(*ctrl));
@@ -699,9 +703,11 @@ r535_outp_acquire(struct nvkm_outp *outp, bool hda)
 	if (hda)
 		ctrl->flags |= NVDEF(NV0073_CTRL, DFP_ASSIGN_SOR_FLAGS, AUDIO, OPTIMAL);
 
-	ctrl = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, ctrl, sizeof(*ctrl));
-	if (IS_ERR(ctrl))
-		return PTR_ERR(ctrl);
+	ret = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, &ctrl, sizeof(*ctrl));
+	if (ret) {
+		nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
+		return ret;
+	}
 
 	for (or = 0; or < ARRAY_SIZE(ctrl->sorAssignListWithTag); or++) {
 		if (ctrl->sorAssignListWithTag[or].displayMask & BIT(outp->index)) {
@@ -727,6 +733,7 @@ static int
 r535_disp_head_displayid(struct nvkm_disp *disp, int head, u32 *displayid)
 {
 	NV0073_CTRL_SYSTEM_GET_ACTIVE_PARAMS *ctrl;
+	int ret;
 
 	ctrl = nvkm_gsp_rm_ctrl_get(&disp->rm.objcom,
 				    NV0073_CTRL_CMD_SYSTEM_GET_ACTIVE, sizeof(*ctrl));
@@ -736,9 +743,11 @@ r535_disp_head_displayid(struct nvkm_disp *disp, int head, u32 *displayid)
 	ctrl->subDeviceInstance = 0;
 	ctrl->head = head;
 
-	ctrl = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, ctrl, sizeof(*ctrl));
-	if (IS_ERR(ctrl))
-		return PTR_ERR(ctrl);
+	ret = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, &ctrl, sizeof(*ctrl));
+	if (ret) {
+		nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
+		return ret;
+	}
 
 	*displayid = ctrl->displayId;
 	nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
@@ -772,9 +781,11 @@ r535_outp_inherit(struct nvkm_outp *outp)
 			ctrl->subDeviceInstance = 0;
 			ctrl->displayId = displayid;
 
-			ctrl = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, ctrl, sizeof(*ctrl));
-			if (IS_ERR(ctrl))
+			ret = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, &ctrl, sizeof(*ctrl));
+			if (ret) {
+				nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
 				return NULL;
+			}
 
 			id = ctrl->index;
 			proto = ctrl->protocol;
@@ -825,6 +836,7 @@ r535_outp_dfp_get_info(struct nvkm_outp *outp)
 {
 	NV0073_CTRL_DFP_GET_INFO_PARAMS *ctrl;
 	struct nvkm_disp *disp = outp->disp;
+	int ret;
 
 	ctrl = nvkm_gsp_rm_ctrl_get(&disp->rm.objcom, NV0073_CTRL_CMD_DFP_GET_INFO, sizeof(*ctrl));
 	if (IS_ERR(ctrl))
@@ -832,9 +844,11 @@ r535_outp_dfp_get_info(struct nvkm_outp *outp)
 
 	ctrl->displayId = BIT(outp->index);
 
-	ctrl = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, ctrl, sizeof(*ctrl));
-	if (IS_ERR(ctrl))
-		return PTR_ERR(ctrl);
+	ret = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, &ctrl, sizeof(*ctrl));
+	if (ret) {
+		nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
+		return ret;
+	}
 
 	nvkm_debug(&disp->engine.subdev, "DFP %08x: flags:%08x flags2:%08x\n",
 		   ctrl->displayId, ctrl->flags, ctrl->flags2);
@@ -858,9 +872,11 @@ r535_outp_detect(struct nvkm_outp *outp)
 	ctrl->subDeviceInstance = 0;
 	ctrl->displayMask = BIT(outp->index);
 
-	ctrl = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, ctrl, sizeof(*ctrl));
-	if (IS_ERR(ctrl))
-		return PTR_ERR(ctrl);
+	ret = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, &ctrl, sizeof(*ctrl));
+	if (ret) {
+		nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
+		return ret;
+	}
 
 	if (ctrl->displayMask & BIT(outp->index)) {
 		ret = r535_outp_dfp_get_info(outp);
@@ -895,6 +911,7 @@ r535_dp_mst_id_get(struct nvkm_outp *outp, u32 *pid)
 {
 	NV0073_CTRL_CMD_DP_TOPOLOGY_ALLOCATE_DISPLAYID_PARAMS *ctrl;
 	struct nvkm_disp *disp = outp->disp;
+	int ret;
 
 	ctrl = nvkm_gsp_rm_ctrl_get(&disp->rm.objcom,
 				    NV0073_CTRL_CMD_DP_TOPOLOGY_ALLOCATE_DISPLAYID,
@@ -904,9 +921,11 @@ r535_dp_mst_id_get(struct nvkm_outp *outp, u32 *pid)
 
 	ctrl->subDeviceInstance = 0;
 	ctrl->displayId = BIT(outp->index);
-	ctrl = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, ctrl, sizeof(*ctrl));
-	if (IS_ERR(ctrl))
-		return PTR_ERR(ctrl);
+	ret = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, &ctrl, sizeof(*ctrl));
+	if (ret) {
+		nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
+		return ret;
+	}
 
 	*pid = ctrl->displayIdAssigned;
 	nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
@@ -964,9 +983,11 @@ r535_dp_train_target(struct nvkm_outp *outp, u8 target, bool mst, u8 link_nr, u8
 	    !(outp->dp.dpcd[DPCD_RC03] & DPCD_RC03_TPS4_SUPPORTED))
 	    ctrl->cmd |= NVDEF(NV0073_CTRL, DP_CMD, POST_LT_ADJ_REQ_GRANTED, YES);
 
-	ctrl = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, ctrl, sizeof(*ctrl));
-	if (IS_ERR(ctrl))
-		return PTR_ERR(ctrl);
+	ret = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, &ctrl, sizeof(*ctrl));
+	if (ret) {
+		nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
+		return ret;
+	}
 
 	ret = ctrl->err ? -EIO : 0;
 	nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
@@ -1036,9 +1057,11 @@ r535_dp_aux_xfer(struct nvkm_outp *outp, u8 type, u32 addr, u8 *data, u8 *psize)
 	ctrl->size = !ctrl->bAddrOnly ? (size - 1) : 0;
 	memcpy(ctrl->data, data, size);
 
-	ctrl = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, ctrl, sizeof(*ctrl));
-	if (IS_ERR(ctrl))
+	ret = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, &ctrl, sizeof(*ctrl));
+	if (ret) {
+		nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
 		return PTR_ERR(ctrl);
+	}
 
 	memcpy(data, ctrl->data, size);
 	*psize = ctrl->size;
@@ -1111,10 +1134,13 @@ r535_tmds_edid_get(struct nvkm_outp *outp, u8 *data, u16 *psize)
 	ctrl->subDeviceInstance = 0;
 	ctrl->displayId = BIT(outp->index);
 
-	ctrl = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, ctrl, sizeof(*ctrl));
-	if (IS_ERR(ctrl))
-		return PTR_ERR(ctrl);
+	ret = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, &ctrl, sizeof(*ctrl));
+	if (ret) {
+		nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
+		return ret;
+	}
 
+	ret = -E2BIG;
 	if (ctrl->bufferSize <= *psize) {
 		memcpy(data, ctrl->edidBuffer, ctrl->bufferSize);
 		*psize = ctrl->bufferSize;
@@ -1153,9 +1179,11 @@ r535_outp_new(struct nvkm_disp *disp, u32 id)
 	ctrl->subDeviceInstance = 0;
 	ctrl->displayId = BIT(id);
 
-	ctrl = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, ctrl, sizeof(*ctrl));
-	if (IS_ERR(ctrl))
-		return PTR_ERR(ctrl);
+	ret = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, &ctrl, sizeof(*ctrl));
+	if (ret) {
+		nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
+		return ret;
+	}
 
 	switch (ctrl->type) {
 	case NV0073_CTRL_SPECIFIC_OR_TYPE_NONE:
@@ -1229,9 +1257,11 @@ r535_outp_new(struct nvkm_disp *disp, u32 id)
 
 		ctrl->sorIndex = ~0;
 
-		ctrl = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, ctrl, sizeof(*ctrl));
-		if (IS_ERR(ctrl))
-			return PTR_ERR(ctrl);
+		ret = nvkm_gsp_rm_ctrl_push(&disp->rm.objcom, &ctrl, sizeof(*ctrl));
+		if (ret) {
+			nvkm_gsp_rm_ctrl_done(&disp->rm.objcom, ctrl);
+			return ret;
+		}
 
 		switch (NVVAL_GET(ctrl->maxLinkRate, NV0073_CTRL_CMD, DP_GET_CAPS, MAX_LINK_RATE)) {
 		case NV0073_CTRL_CMD_DP_GET_CAPS_MAX_LINK_RATE_1_62:
diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c b/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
index 54c1fbccc013..e2810fd1a36f 100644
--- a/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
@@ -599,13 +599,13 @@ r535_gsp_rpc_rm_alloc_push(struct nvkm_gsp_object *object, void *argv, u32 repc)
 
 	if (rpc->status) {
 		ret = ERR_PTR(r535_rpc_status_to_errno(rpc->status));
-		if (ret != -EAGAIN)
+		if (PTR_ERR(ret) != -EAGAIN)
 			nvkm_error(&gsp->subdev, "RM_ALLOC: 0x%x\n", rpc->status);
 	} else {
 		ret = repc ? rpc->params : NULL;
 	}
 
-	if (IS_ERR_OR_NULL(ret))
+	if (ret)
 		nvkm_gsp_rpc_done(gsp, rpc);
 
 	return ret;
@@ -639,30 +639,34 @@ r535_gsp_rpc_rm_ctrl_done(struct nvkm_gsp_object *object, void *repv)
 {
 	rpc_gsp_rm_control_v03_00 *rpc = container_of(repv, typeof(*rpc), params);
 
+	if (!repv)
+		return;
 	nvkm_gsp_rpc_done(object->client->gsp, rpc);
 }
 
-static void *
-r535_gsp_rpc_rm_ctrl_push(struct nvkm_gsp_object *object, void *argv, u32 repc)
+static int
+r535_gsp_rpc_rm_ctrl_push(struct nvkm_gsp_object *object, void **argv, u32 repc)
 {
-	rpc_gsp_rm_control_v03_00 *rpc = container_of(argv, typeof(*rpc), params);
+	rpc_gsp_rm_control_v03_00 *rpc = container_of((*argv), typeof(*rpc), params);
 	struct nvkm_gsp *gsp = object->client->gsp;
-	void *ret;
+	int ret = 0;
 
 	rpc = nvkm_gsp_rpc_push(gsp, rpc, true, repc);
-	if (IS_ERR_OR_NULL(rpc))
-		return rpc;
+	if (IS_ERR_OR_NULL(rpc)) {
+		*argv = NULL;
+		return PTR_ERR(rpc);
+	}
 
 	if (rpc->status) {
-		ret = ERR_PTR(r535_rpc_status_to_errno(rpc->status));
+		ret = r535_rpc_status_to_errno(rpc->status);
 		if (ret != -EAGAIN)
 			nvkm_error(&gsp->subdev, "cli:0x%08x obj:0x%08x ctrl cmd:0x%08x failed: 0x%08x\n",
 				   object->client->object.handle, object->handle, rpc->cmd, rpc->status);
-	} else {
-		ret = repc ? rpc->params : NULL;
 	}
 
-	if (IS_ERR_OR_NULL(ret))
+	if (repc)
+		*argv = rpc->params;
+	else
 		nvkm_gsp_rpc_done(gsp, rpc);
 
 	return ret;
@@ -860,9 +864,11 @@ r535_gsp_intr_get_table(struct nvkm_gsp *gsp)
 	if (IS_ERR(ctrl))
 		return PTR_ERR(ctrl);
 
-	ctrl = nvkm_gsp_rm_ctrl_push(&gsp->internal.device.subdevice, ctrl, sizeof(*ctrl));
-	if (WARN_ON(IS_ERR(ctrl)))
-		return PTR_ERR(ctrl);
+	ret = nvkm_gsp_rm_ctrl_push(&gsp->internal.device.subdevice, &ctrl, sizeof(*ctrl));
+	if (WARN_ON(ret)) {
+		nvkm_gsp_rm_ctrl_done(&gsp->internal.device.subdevice, ctrl);
+		return ret;
+	}
 
 	for (unsigned i = 0; i < ctrl->tableLen; i++) {
 		enum nvkm_subdev_type type;
-- 
2.43.0

Re: [PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors

[Dan Carpenter]

Hi Dave,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Dave-Airlie/nouveau-gsp-drop-some-acpi-related-debug/20231222-180432
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/20231222043308.3090089-9-airlied%40gmail.com
patch subject: [PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors
config: powerpc-randconfig-r071-20231226 (https://download.01.org/0day-ci/archive/20231227/202312271917.55xuDMdc-lkp@intel.com/config)
compiler: clang version 18.0.0git (https://github.com/llvm/llvm-project d3ef86708241a3bee902615c190dead1638c4e09)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
| Closes: https://lore.kernel.org/r/202312271917.55xuDMdc-lkp@intel.com/

New smatch warnings:
drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:659 r535_gsp_rpc_rm_ctrl_push() warn: passing zero to 'PTR_ERR'
drivers/gpu/drm/nouveau/nvkm/engine/disp/r535.c:1063 r535_dp_aux_xfer() warn: passing a valid pointer to 'PTR_ERR'

Old smatch warnings:
drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1887 nvkm_gsp_radix3_sg() error: uninitialized symbol 'addr'.

vim +/PTR_ERR +659 drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c

af265ee961627a Dave Airlie 2023-12-22  649  static int
af265ee961627a Dave Airlie 2023-12-22  650  r535_gsp_rpc_rm_ctrl_push(struct nvkm_gsp_object *object, void **argv, u32 repc)
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  651  {
af265ee961627a Dave Airlie 2023-12-22  652  	rpc_gsp_rm_control_v03_00 *rpc = container_of((*argv), typeof(*rpc), params);
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  653  	struct nvkm_gsp *gsp = object->client->gsp;
af265ee961627a Dave Airlie 2023-12-22  654  	int ret = 0;
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  655  
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  656  	rpc = nvkm_gsp_rpc_push(gsp, rpc, true, repc);
af265ee961627a Dave Airlie 2023-12-22  657  	if (IS_ERR_OR_NULL(rpc)) {
af265ee961627a Dave Airlie 2023-12-22  658  		*argv = NULL;
af265ee961627a Dave Airlie 2023-12-22 @659  		return PTR_ERR(rpc);

If nvkm_gsp_rpc_push() returns NULL (probably a failure) then this
returns PTR_ERR(NULL) which is zero/success.

af265ee961627a Dave Airlie 2023-12-22  660  	}
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  661  
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  662  	if (rpc->status) {
af265ee961627a Dave Airlie 2023-12-22  663  		ret = r535_rpc_status_to_errno(rpc->status);
555bb9c29a45be Dave Airlie 2023-12-22  664  		if (ret != -EAGAIN)
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  665  			nvkm_error(&gsp->subdev, "cli:0x%08x obj:0x%08x ctrl cmd:0x%08x failed: 0x%08x\n",
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  666  				   object->client->object.handle, object->handle, rpc->cmd, rpc->status);
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  667  	}
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  668  
af265ee961627a Dave Airlie 2023-12-22  669  	if (repc)
af265ee961627a Dave Airlie 2023-12-22  670  		*argv = rpc->params;
af265ee961627a Dave Airlie 2023-12-22  671  	else
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  672  		nvkm_gsp_rpc_done(gsp, rpc);
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  673  
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  674  	return ret;
4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  675  }

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors

[Dave Airlie]

On Thu, 4 Jan 2024 at 00:47, Dan Carpenter <dan.carpenter@linaro.org> wrote:
>
> Hi Dave,
>
> kernel test robot noticed the following build warnings:
>
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Dave-Airlie/nouveau-gsp-drop-some-acpi-related-debug/20231222-180432
> base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
> patch link:    https://lore.kernel.org/r/20231222043308.3090089-9-airlied%40gmail.com
> patch subject: [PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors
> config: powerpc-randconfig-r071-20231226 (https://download.01.org/0day-ci/archive/20231227/202312271917.55xuDMdc-lkp@intel.com/config)
> compiler: clang version 18.0.0git (https://github.com/llvm/llvm-project d3ef86708241a3bee902615c190dead1638c4e09)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> | Closes: https://lore.kernel.org/r/202312271917.55xuDMdc-lkp@intel.com/

This is a false positive, I think the code is operating like I'd
expect, we maybe could restructure it to avoid this warning?

The idea is you send an rpc msg, if there's a reply you get a reply,
if no reply you get NULL and if an error you get an error.

So in the case you get an error or NULL you just want to return 0 for
the NULL as it's successful, and error otherwise.

Would using PTR_ERR_OR_ZERO make smatch happy? (even if it's not
really what we want).

Dave.
>
> New smatch warnings:
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:659 r535_gsp_rpc_rm_ctrl_push() warn: passing zero to 'PTR_ERR'
> drivers/gpu/drm/nouveau/nvkm/engine/disp/r535.c:1063 r535_dp_aux_xfer() warn: passing a valid pointer to 'PTR_ERR'
>
> Old smatch warnings:
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1887 nvkm_gsp_radix3_sg() error: uninitialized symbol 'addr'.
>
> vim +/PTR_ERR +659 drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
>
> af265ee961627a Dave Airlie 2023-12-22  649  static int
> af265ee961627a Dave Airlie 2023-12-22  650  r535_gsp_rpc_rm_ctrl_push(struct nvkm_gsp_object *object, void **argv, u32 repc)
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  651  {
> af265ee961627a Dave Airlie 2023-12-22  652      rpc_gsp_rm_control_v03_00 *rpc = container_of((*argv), typeof(*rpc), params);
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  653      struct nvkm_gsp *gsp = object->client->gsp;
> af265ee961627a Dave Airlie 2023-12-22  654      int ret = 0;
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  655
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  656      rpc = nvkm_gsp_rpc_push(gsp, rpc, true, repc);
> af265ee961627a Dave Airlie 2023-12-22  657      if (IS_ERR_OR_NULL(rpc)) {
> af265ee961627a Dave Airlie 2023-12-22  658              *argv = NULL;
> af265ee961627a Dave Airlie 2023-12-22 @659              return PTR_ERR(rpc);
>
> If nvkm_gsp_rpc_push() returns NULL (probably a failure) then this
> returns PTR_ERR(NULL) which is zero/success.
>
> af265ee961627a Dave Airlie 2023-12-22  660      }
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  661
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  662      if (rpc->status) {
> af265ee961627a Dave Airlie 2023-12-22  663              ret = r535_rpc_status_to_errno(rpc->status);
> 555bb9c29a45be Dave Airlie 2023-12-22  664              if (ret != -EAGAIN)
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  665                      nvkm_error(&gsp->subdev, "cli:0x%08x obj:0x%08x ctrl cmd:0x%08x failed: 0x%08x\n",
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  666                                 object->client->object.handle, object->handle, rpc->cmd, rpc->status);
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  667      }
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  668
> af265ee961627a Dave Airlie 2023-12-22  669      if (repc)
> af265ee961627a Dave Airlie 2023-12-22  670              *argv = rpc->params;
> af265ee961627a Dave Airlie 2023-12-22  671      else
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  672              nvkm_gsp_rpc_done(gsp, rpc);
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  673
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  674      return ret;
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  675  }
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki
>

Re: [PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors

[Dave Airlie]

On Thu, 4 Jan 2024 at 00:47, Dan Carpenter <dan.carpenter@linaro.org> wrote:
>
> Hi Dave,
>
> kernel test robot noticed the following build warnings:
>
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Dave-Airlie/nouveau-gsp-drop-some-acpi-related-debug/20231222-180432
> base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
> patch link:    https://lore.kernel.org/r/20231222043308.3090089-9-airlied%40gmail.com
> patch subject: [PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors
> config: powerpc-randconfig-r071-20231226 (https://download.01.org/0day-ci/archive/20231227/202312271917.55xuDMdc-lkp@intel.com/config)
> compiler: clang version 18.0.0git (https://github.com/llvm/llvm-project d3ef86708241a3bee902615c190dead1638c4e09)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> | Closes: https://lore.kernel.org/r/202312271917.55xuDMdc-lkp@intel.com/

This is a false positive, I think the code is operating like I'd
expect, we maybe could restructure it to avoid this warning?

The idea is you send an rpc msg, if there's a reply you get a reply,
if no reply you get NULL and if an error you get an error.

So in the case you get an error or NULL you just want to return 0 for
the NULL as it's successful, and error otherwise.

Would using PTR_ERR_OR_ZERO make smatch happy? (even if it's not
really what we want).

Dave.
>
> New smatch warnings:
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:659 r535_gsp_rpc_rm_ctrl_push() warn: passing zero to 'PTR_ERR'
> drivers/gpu/drm/nouveau/nvkm/engine/disp/r535.c:1063 r535_dp_aux_xfer() warn: passing a valid pointer to 'PTR_ERR'
>
> Old smatch warnings:
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1887 nvkm_gsp_radix3_sg() error: uninitialized symbol 'addr'.
>
> vim +/PTR_ERR +659 drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c
>
> af265ee961627a Dave Airlie 2023-12-22  649  static int
> af265ee961627a Dave Airlie 2023-12-22  650  r535_gsp_rpc_rm_ctrl_push(struct nvkm_gsp_object *object, void **argv, u32 repc)
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  651  {
> af265ee961627a Dave Airlie 2023-12-22  652      rpc_gsp_rm_control_v03_00 *rpc = container_of((*argv), typeof(*rpc), params);
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  653      struct nvkm_gsp *gsp = object->client->gsp;
> af265ee961627a Dave Airlie 2023-12-22  654      int ret = 0;
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  655
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  656      rpc = nvkm_gsp_rpc_push(gsp, rpc, true, repc);
> af265ee961627a Dave Airlie 2023-12-22  657      if (IS_ERR_OR_NULL(rpc)) {
> af265ee961627a Dave Airlie 2023-12-22  658              *argv = NULL;
> af265ee961627a Dave Airlie 2023-12-22 @659              return PTR_ERR(rpc);
>
> If nvkm_gsp_rpc_push() returns NULL (probably a failure) then this
> returns PTR_ERR(NULL) which is zero/success.
>
> af265ee961627a Dave Airlie 2023-12-22  660      }
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  661
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  662      if (rpc->status) {
> af265ee961627a Dave Airlie 2023-12-22  663              ret = r535_rpc_status_to_errno(rpc->status);
> 555bb9c29a45be Dave Airlie 2023-12-22  664              if (ret != -EAGAIN)
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  665                      nvkm_error(&gsp->subdev, "cli:0x%08x obj:0x%08x ctrl cmd:0x%08x failed: 0x%08x\n",
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  666                                 object->client->object.handle, object->handle, rpc->cmd, rpc->status);
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  667      }
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  668
> af265ee961627a Dave Airlie 2023-12-22  669      if (repc)
> af265ee961627a Dave Airlie 2023-12-22  670              *argv = rpc->params;
> af265ee961627a Dave Airlie 2023-12-22  671      else
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  672              nvkm_gsp_rpc_done(gsp, rpc);
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  673
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  674      return ret;
> 4cf2c83eb3a4c4 Ben Skeggs  2023-09-19  675  }
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki
>

Re: [PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors

[Dan Carpenter]

On Thu, Jan 04, 2024 at 10:41:50AM +1000, Dave Airlie wrote:
> On Thu, 4 Jan 2024 at 00:47, Dan Carpenter <dan.carpenter@linaro.org> wrote:
> >
> > Hi Dave,
> >
> > kernel test robot noticed the following build warnings:
> >
> > https://git-scm.com/docs/git-format-patch#_base_tree_information]
> >
> > url:    https://github.com/intel-lab-lkp/linux/commits/Dave-Airlie/nouveau-gsp-drop-some-acpi-related-debug/20231222-180432
> > base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
> > patch link:    https://lore.kernel.org/r/20231222043308.3090089-9-airlied%40gmail.com
> > patch subject: [PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors
> > config: powerpc-randconfig-r071-20231226 (https://download.01.org/0day-ci/archive/20231227/202312271917.55xuDMdc-lkp@intel.com/config)
> > compiler: clang version 18.0.0git (https://github.com/llvm/llvm-project d3ef86708241a3bee902615c190dead1638c4e09)
> >
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> > | Closes: https://lore.kernel.org/r/202312271917.55xuDMdc-lkp@intel.com/
> 
> This is a false positive, I think the code is operating like I'd
> expect, we maybe could restructure it to avoid this warning?
> 
> The idea is you send an rpc msg, if there's a reply you get a reply,
> if no reply you get NULL and if an error you get an error.
> 
> So in the case you get an error or NULL you just want to return 0 for
> the NULL as it's successful, and error otherwise.
> 
> Would using PTR_ERR_OR_ZERO make smatch happy? (even if it's not
> really what we want).

Hm...  You're using the API correctly.  Linus has complained about this
warning before but in new code over 90% of the warnings are correct.
It's a high quality warning.

I looked around for an explanation to see what the NULL meant but
couldn't find it documented in the code.  The NULL vs error pointer comes
from a function pointer and it's not always clear where the
documentation should be with a function pointer.  So perhaps I missed it.

Let's not use PTR_ERR_OR_ZERO.  Perhaps I should introduce a
PTR_ERR_OR_NULL() macro to silence this warning.  But most of the code
which does this correctly is in fs/ and they probably are like Linus and
would be surprised to learn that people get it wrong...

regards,
dan carpenter

Re: [PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors

[Dan Carpenter]

On Thu, Jan 04, 2024 at 10:41:50AM +1000, Dave Airlie wrote:
> On Thu, 4 Jan 2024 at 00:47, Dan Carpenter <dan.carpenter@linaro.org> wrote:
> >
> > Hi Dave,
> >
> > kernel test robot noticed the following build warnings:
> >
> > https://git-scm.com/docs/git-format-patch#_base_tree_information]
> >
> > url:    https://github.com/intel-lab-lkp/linux/commits/Dave-Airlie/nouveau-gsp-drop-some-acpi-related-debug/20231222-180432
> > base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
> > patch link:    https://lore.kernel.org/r/20231222043308.3090089-9-airlied%40gmail.com
> > patch subject: [PATCH 08/11] nouveau/gsp: don't free ctrl messages on errors
> > config: powerpc-randconfig-r071-20231226 (https://download.01.org/0day-ci/archive/20231227/202312271917.55xuDMdc-lkp@intel.com/config)
> > compiler: clang version 18.0.0git (https://github.com/llvm/llvm-project d3ef86708241a3bee902615c190dead1638c4e09)
> >
> > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > the same patch/commit), kindly add following tags
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
> > | Closes: https://lore.kernel.org/r/202312271917.55xuDMdc-lkp@intel.com/
> 
> This is a false positive, I think the code is operating like I'd
> expect, we maybe could restructure it to avoid this warning?
> 
> The idea is you send an rpc msg, if there's a reply you get a reply,
> if no reply you get NULL and if an error you get an error.
> 
> So in the case you get an error or NULL you just want to return 0 for
> the NULL as it's successful, and error otherwise.
> 
> Would using PTR_ERR_OR_ZERO make smatch happy? (even if it's not
> really what we want).

Hm...  You're using the API correctly.  Linus has complained about this
warning before but in new code over 90% of the warnings are correct.
It's a high quality warning.

I looked around for an explanation to see what the NULL meant but
couldn't find it documented in the code.  The NULL vs error pointer comes
from a function pointer and it's not always clear where the
documentation should be with a function pointer.  So perhaps I missed it.

Let's not use PTR_ERR_OR_ZERO.  Perhaps I should introduce a
PTR_ERR_OR_NULL() macro to silence this warning.  But most of the code
which does this correctly is in fs/ and they probably are like Linus and
would be surprised to learn that people get it wrong...

regards,
dan carpenter