drm/amd/pm: Replace one-element array with flexible-array in struct phm_samu_clock_vo...

There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use “flexible array members”[1] for these cases. The older
style of one-element or zero-length arrays should no longer be used[2].

Refactor the code according to the use of a flexible-array member in
struct phm_samu_clock_voltage_dependency_table, instead of a one-element array,
and use the struct_size() helper to calculate the size for the allocation.

Also, save some heap space as the original code is multiplying
table->numEntries by sizeof(struct phm_samu_clock_voltage_dependency_table)
when it should have been multiplied it by
sizeof(struct phm_samu_clock_voltage_dependency_record) instead.

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays

Build-tested-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/lkml/5f7c5d3a.ryM4GmZr3e0JeZy+%25lkp@intel.com/
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/pm/inc/hwmgr.h b/drivers/gpu/drm/amd/pm/inc/hwmgr.h
index 7e0c948..dad703b 100644 (file)
--- a/drivers/gpu/drm/amd/pm/inc/hwmgr.h
+++ b/drivers/gpu/drm/amd/pm/inc/hwmgr.h
@@ -404,7 +404,7 @@ struct phm_samu_clock_voltage_dependency_record {
 
 struct phm_samu_clock_voltage_dependency_table {
        uint8_t count;
-       struct phm_samu_clock_voltage_dependency_record entries[1];
+       struct phm_samu_clock_voltage_dependency_record entries[];
 };
 
 struct phm_cac_tdp_table {

diff --git a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/processpptables.c b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/processpptables.c
index e059802..48d550d 100644 (file)
--- a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/processpptables.c
+++ b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/processpptables.c
@@ -1163,15 +1163,12 @@ static int get_samu_clock_voltage_limit_table(struct pp_hwmgr *hwmgr,
                 struct phm_samu_clock_voltage_dependency_table **ptable,
                 const ATOM_PPLIB_SAMClk_Voltage_Limit_Table *table)
 {
-       unsigned long table_size, i;
+       unsigned long i;
        struct phm_samu_clock_voltage_dependency_table *samu_table;
 
-       table_size = sizeof(unsigned long) +
-               sizeof(struct phm_samu_clock_voltage_dependency_table) *
-               table->numEntries;
-
-       samu_table = kzalloc(table_size, GFP_KERNEL);
-       if (NULL == samu_table)
+       samu_table = kzalloc(struct_size(samu_table, entries, table->numEntries),
+                            GFP_KERNEL);
+       if (!samu_table)
                return -ENOMEM;
 
        samu_table->count = table->numEntries;