[Intel-gfx] [bug report] drm/i915/dmc: add i915_to_dmc() and dmc->i915 and use them

[Jani Nikula]

On Thu, 09 Mar 2023, Dan Carpenter <error27 at gmail.com> wrote:
> Hello Jani Nikula,
>
> This is a semi-automatic email about new static checker warnings.
>
> The patch 1b28c1c789d0: "drm/i915/dmc: add i915_to_dmc() and 
> dmc->i915 and use them" from Mar 1, 2023, leads to the following 
> Smatch complaint:
>
>     drivers/gpu/drm/i915/display/intel_dmc.c:1162 intel_dmc_debugfs_status_show()
>     error: we previously assumed 'dmc' could be null (see line 1148)
>
> drivers/gpu/drm/i915/display/intel_dmc.c
>   1142  
>   1143          wakeref = intel_runtime_pm_get(&i915->runtime_pm);
>   1144  
>   1145          seq_printf(m, "DMC initialized: %s\n", str_yes_no(dmc));'
>                                                        ^^^^^^^^^^^^^^^
> This is a check for NULL too.
>
>   1146          seq_printf(m, "fw loaded: %s\n",
>   1147			   str_yes_no(intel_dmc_has_payload(i915)));
>   1148		seq_printf(m, "path: %s\n", dmc ? dmc->fw_path : "N/A");
>                                             ^^^
> The patch adds a check for NULL.
>
>   1149		seq_printf(m, "Pipe A fw needed: %s\n",
>   1150			   str_yes_no(GRAPHICS_VER(i915) >= 12));
>   1151		seq_printf(m, "Pipe A fw loaded: %s\n",
>   1152			   str_yes_no(has_dmc_id_fw(i915, DMC_FW_PIPEA)));
>   1153		seq_printf(m, "Pipe B fw needed: %s\n",
>   1154			   str_yes_no(IS_ALDERLAKE_P(i915) ||
>   1155				      DISPLAY_VER(i915) >= 14));
>   1156		seq_printf(m, "Pipe B fw loaded: %s\n",
>   1157			   str_yes_no(has_dmc_id_fw(i915, DMC_FW_PIPEB)));
>   1158	
>   1159		if (!intel_dmc_has_payload(i915))

intel_dmc_has_payload() should always return false for dmc == NULL.

BR,
Jani.

>   1160			goto out;
>   1161	
>   1162		seq_printf(m, "version: %d.%d\n", DMC_VERSION_MAJOR(dmc->version),
>                                                                     ^^^^^^^^^^^^
>   1163			   DMC_VERSION_MINOR(dmc->version));
>                                              ^^^^^^^^^^^^
> Unchecked dereferences.
>
>   1164	
>
> regards,
> dan carpenter

-- 
Jani Nikula, Intel Open Source Graphics Center