gpu: amd: replace open-coded offsetof() with builtin

The two AMD drivers have their own custom offsetof() implementation
that now triggers a warning with recent versions of clang:

drivers/gpu/drm/radeon/radeon_atombios.c:133:14: error: performing pointer subtraction with a null pointer has undefined behavior [-Werror,-Wnull-pointer-subtraction]

Change all the instances to use the normal offsetof() provided
by the kernel that does not have this problem.

Signed-off-by: Arnd Bergmann <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dc/bios/command_table2.c

···
 	bp->base.ctx->logger
 
 #define GET_INDEX_INTO_MASTER_TABLE(MasterOrData, FieldName)\
-	(((char *)(&((\
-		struct atom_master_list_of_##MasterOrData##_functions_v2_1 *)0)\
-		->FieldName)-(char *)0)/sizeof(uint16_t))
+	(offsetof(struct atom_master_list_of_##MasterOrData##_functions_v2_1, FieldName) / sizeof(uint16_t))
 
 #define EXEC_BIOS_CMD_TABLE(fname, params)\
 	(amdgpu_atom_execute_table(((struct amdgpu_device *)bp->base.ctx->driver_context)->mode_info.atom_context, \

drivers/gpu/drm/amd/include/atombios.h

···
 #define GET_COMMAND_TABLE_COMMANDSET_REVISION(TABLE_HEADER_OFFSET) (((static_cast<ATOM_COMMON_TABLE_HEADER*>(TABLE_HEADER_OFFSET))->ucTableFormatRevision )&0x3F)
 #define GET_COMMAND_TABLE_PARAMETER_REVISION(TABLE_HEADER_OFFSET)  (((static_cast<ATOM_COMMON_TABLE_HEADER*>(TABLE_HEADER_OFFSET))->ucTableContentRevision)&0x3F)
 #else // not __cplusplus
-#define   GetIndexIntoMasterTable(MasterOrData, FieldName) (((char*)(&((ATOM_MASTER_LIST_OF_##MasterOrData##_TABLES*)0)->FieldName)-(char*)0)/sizeof(USHORT))
+#define   GetIndexIntoMasterTable(MasterOrData, FieldName) (offsetof(ATOM_MASTER_LIST_OF_##MasterOrData##_TABLES, FieldName) / sizeof(USHORT))
 
 #define GET_COMMAND_TABLE_COMMANDSET_REVISION(TABLE_HEADER_OFFSET) ((((ATOM_COMMON_TABLE_HEADER*)TABLE_HEADER_OFFSET)->ucTableFormatRevision)&0x3F)
 #define GET_COMMAND_TABLE_PARAMETER_REVISION(TABLE_HEADER_OFFSET)  ((((ATOM_COMMON_TABLE_HEADER*)TABLE_HEADER_OFFSET)->ucTableContentRevision)&0x3F)

drivers/gpu/drm/amd/pm/powerplay/hwmgr/ppatomfwctrl.h

···
 typedef enum atom_smu9_syspll0_clock_id BIOS_CLKID;
 
 #define GetIndexIntoMasterCmdTable(FieldName) \
-	(((char*)(&((struct atom_master_list_of_command_functions_v2_1*)0)->FieldName)-(char*)0)/sizeof(uint16_t))
+	(offsetof(struct atom_master_list_of_command_functions_v2_1, FieldName) / sizeof(uint16_t))
 #define GetIndexIntoMasterDataTable(FieldName) \
-	(((char*)(&((struct atom_master_list_of_data_tables_v2_1*)0)->FieldName)-(char*)0)/sizeof(uint16_t))
+	(offsetof(struct atom_master_list_of_data_tables_v2_1, FieldName) / sizeof(uint16_t))
 
 #define PP_ATOMFWCTRL_MAX_VOLTAGE_ENTRIES 32
 

drivers/gpu/drm/radeon/atombios.h

···
 #define GET_COMMAND_TABLE_COMMANDSET_REVISION(TABLE_HEADER_OFFSET) (((static_cast<ATOM_COMMON_TABLE_HEADER*>(TABLE_HEADER_OFFSET))->ucTableFormatRevision )&0x3F)
 #define GET_COMMAND_TABLE_PARAMETER_REVISION(TABLE_HEADER_OFFSET)  (((static_cast<ATOM_COMMON_TABLE_HEADER*>(TABLE_HEADER_OFFSET))->ucTableContentRevision)&0x3F)
 #else // not __cplusplus
-#define	GetIndexIntoMasterTable(MasterOrData, FieldName) (((char*)(&((ATOM_MASTER_LIST_OF_##MasterOrData##_TABLES*)0)->FieldName)-(char*)0)/sizeof(USHORT))
+#define	GetIndexIntoMasterTable(MasterOrData, FieldName) (offsetof(ATOM_MASTER_LIST_OF_##MasterOrData##_TABLES, FieldName)/sizeof(USHORT))
 
 #define GET_COMMAND_TABLE_COMMANDSET_REVISION(TABLE_HEADER_OFFSET) ((((ATOM_COMMON_TABLE_HEADER*)TABLE_HEADER_OFFSET)->ucTableFormatRevision)&0x3F)
 #define GET_COMMAND_TABLE_PARAMETER_REVISION(TABLE_HEADER_OFFSET)  ((((ATOM_COMMON_TABLE_HEADER*)TABLE_HEADER_OFFSET)->ucTableContentRevision)&0x3F)