linux-kernel - [PATCH] drm/amd/powerplay/smu10_hwmgr: use struct

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Date:   Tue, 19 Feb 2019 12:55:09 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Rex Zhu <rex.zhu@....com>, Evan Quan <evan.quan@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] drm/amd/powerplay/smu10_hwmgr: use struct_size() in kzalloc()

One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct foo {
    int stuff;
    struct boo entry[];
};

size = sizeof(struct foo) + count * sizeof(struct boo);
instance = kzalloc(size, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can
now use the new struct_size() helper:

instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);

Notice that, in this case, variable table_size is not necessary, hence
it is removed.

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
index 5273de3c5b98..0ad8fe4a6277 100644
--- a/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
+++ b/drivers/gpu/drm/amd/powerplay/hwmgr/smu10_hwmgr.c
@@ -139,12 +139,10 @@ static int smu10_construct_max_power_limits_table(struct pp_hwmgr *hwmgr,
 static int smu10_init_dynamic_state_adjustment_rule_settings(
 							struct pp_hwmgr *hwmgr)
 {
-	uint32_t table_size =
-		sizeof(struct phm_clock_voltage_dependency_table) +
-		(7 * sizeof(struct phm_clock_voltage_dependency_record));
+	struct phm_clock_voltage_dependency_table *table_clk_vlt;
 
-	struct phm_clock_voltage_dependency_table *table_clk_vlt =
-					kzalloc(table_size, GFP_KERNEL);
+	table_clk_vlt = kzalloc(struct_size(table_clk_vlt, entries, 7),
+				GFP_KERNEL);
 
 	if (NULL == table_clk_vlt) {
 		pr_err("Can not allocate memory!\n");
-- 
2.20.1