[PATCH v3 1/2] drm/display/dsc: Refactor DRM MST DSC Determination Policy

[Dan Carpenter]

Hi Fangzhi,

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/Fangzhi-Zuo/drm-display-dsc-Refactor-DRM-MST-DSC-Determination-Policy/20241106-230854
base:   git://anongit.freedesktop.org/drm/drm drm-next
patch link:    https://lore.kernel.org/r/20241106150444.424579-2-Jerry.Zuo%40amd.com
patch subject: [PATCH v3 1/2] drm/display/dsc: Refactor DRM MST DSC Determination Policy
config: i386-randconfig-141-20241107 (https://download.01.org/0day-ci/archive/20241107/202411071102.0CMTIEIo-lkp@intel.com/config)
compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)

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 at intel.com>
| Reported-by: Dan Carpenter <dan.carpenter at linaro.org>
| Closes: https://lore.kernel.org/r/202411071102.0CMTIEIo-lkp@intel.com/

smatch warnings:
drivers/gpu/drm/display/drm_dp_mst_topology.c:6043 drm_dp_mst_dsc_aux_for_port() warn: variable dereferenced before check 'port' (see line 6033)

vim +/port +6043 drivers/gpu/drm/display/drm_dp_mst_topology.c

c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis 2019-08-26  6031  struct drm_dp_aux *drm_dp_mst_dsc_aux_for_port(struct drm_dp_mst_port *port)
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis 2019-08-26  6032  {
fd05275592ae07 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo   2024-11-06 @6033  	struct drm_dp_mst_topology_mgr *mgr = port->mgr;
                                                                                                                                      ^^^^^^^^^
Dereferenced

fd05275592ae07 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo   2024-11-06  6034  	struct drm_dp_mst_port *immediate_upstream_port = NULL;
fd05275592ae07 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo   2024-11-06  6035  	struct drm_dp_mst_port *fec_port = NULL;
fd05275592ae07 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo   2024-11-06  6036  	struct drm_dp_mst_port *dsc_port = NULL;
fd05275592ae07 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo   2024-11-06  6037  	struct drm_dp_aux *upstream_aux;
fd05275592ae07 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo   2024-11-06  6038  	bool end_has_dpcd = (port->dpcd_rev > 0);
fd05275592ae07 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo   2024-11-06  6039  	u8 endpoint_dsc = 0;
70a6587dca37a3 drivers/gpu/drm/display/drm_dp_mst_topology.c Imre Deak     2024-09-09  6040  	u8 upstream_dsc;
fd05275592ae07 drivers/gpu/drm/display/drm_dp_mst_topology.c Fangzhi Zuo   2024-11-06  6041  	u8 fec_cap;
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis 2019-08-26  6042  
c2bc1b6eabe65d drivers/gpu/drm/drm_dp_mst_topology.c         David Francis 2019-08-26 @6043  	if (!port)
                                                                                                    ^^^^^
Checked too late.

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