[bug report] drm/amd/display: Move link functions from dc to dc_link

[Dan Carpenter]

Hello Chris Park,

This is a semi-automatic email about new static checker warnings.

The patch f5692f69f673: "drm/amd/display: Move link functions from dc 
to dc_link" from May 10, 2019, leads to the following Smatch 
complaint:

    drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_link.c:2929 dc_link_set_preferred_link_settings()
    warn: variable dereferenced before check 'link_stream' (see line 2926)

drivers/gpu/drm/amd/amdgpu/../display/dc/core/dc_link.c
  2911          for (i = 0; i < MAX_PIPES; i++) {
  2912                  pipe = &dc->current_state->res_ctx.pipe_ctx[i];
  2913                  if (pipe->stream && pipe->stream->link) {
  2914                          if (pipe->stream->link == link)
  2915                                  break;
  2916                  }
  2917          }
  2918  
  2919          /* Stream not found */
  2920          if (i == MAX_PIPES)
  2921                  return;
  2922  
  2923          link_stream = link->dc->current_state->res_ctx.pipe_ctx[i].stream;
  2924  
  2925		/* Cannot retrain link if backend is off */
  2926		if (link_stream->dpms_off)
                    ^^^^^^^^^^^^^^^^^^^^^
Can link_stream be NULL?

  2927			return;
  2928	
  2929		if (link_stream)
                    ^^^^^^^^^^^
We check here so maybe?

  2930			decide_link_settings(link_stream, &store_settings);
  2931	

regards,
dan carpenter