linux-kernel - [PATCH v2] regmap: sdw-mbq: Reorder regmap_mbq

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Message-ID: <20251107104551.1553526-1-ckeepax@opensource.cirrus.com>
Date: Fri,  7 Nov 2025 10:45:51 +0000
From: Charles Keepax <ckeepax@...nsource.cirrus.com>
To: broonie@...nel.org
Cc: linux-kernel@...r.kernel.org, patches@...nsource.cirrus.com
Subject: [PATCH v2] regmap: sdw-mbq: Reorder regmap_mbq_context struct for better packing

Avoid a hole in struct regmap_mbq_context by shuffling the members
slightly. Pahole before:

struct regmap_mbq_context {
        struct device *            dev;                  /*     0     8 */
        struct sdw_slave *         sdw;                  /*     8     8 */
        struct regmap_sdw_mbq_cfg  cfg;                  /*    16    32 */
        int                        val_size;             /*    48     4 */

        /* XXX 4 bytes hole, try to pack */

        bool                       (*readable_reg)(struct device *, unsigned int); /*    56     8 */

        /* size: 64, cachelines: 1, members: 5 */
        /* sum members: 60, holes: 1, sum holes: 4 */
};

Pahole after:

struct regmap_mbq_context {
        struct device *            dev;                  /*     0     8 */
        struct sdw_slave *         sdw;                  /*     8     8 */
        bool                       (*readable_reg)(struct device *, unsigned int); /*    16     8 */
        struct regmap_sdw_mbq_cfg  cfg;                  /*    24    32 */
        int                        val_size;             /*    56     4 */

        /* size: 64, cachelines: 1, members: 5 */
        /* padding: 4 */
};

Signed-off-by: Charles Keepax <ckeepax@...nsource.cirrus.com>
---

Changes since v1:
 - Update commit description to include pahole outputs before and after

 drivers/base/regmap/regmap-sdw-mbq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/base/regmap/regmap-sdw-mbq.c b/drivers/base/regmap/regmap-sdw-mbq.c
index 86644bbd07100..225c158d7f9d7 100644
--- a/drivers/base/regmap/regmap-sdw-mbq.c
+++ b/drivers/base/regmap/regmap-sdw-mbq.c
@@ -16,10 +16,11 @@
 struct regmap_mbq_context {
 	struct device *dev;
 
+	bool (*readable_reg)(struct device *dev, unsigned int reg);
+
 	struct regmap_sdw_mbq_cfg cfg;
 
 	int val_size;
-	bool (*readable_reg)(struct device *dev, unsigned int reg);
 };
 
 static int regmap_sdw_mbq_size(struct regmap_mbq_context *ctx, unsigned int reg)
-- 
2.47.3