linux-kernel - [PATCH] regmap: Check for register readability before checking cache during read

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Message-Id: <20230613-b4-regmap-check-readability-before-cache-v1-1-b144c0b01ed9@kernel.org>
Date:   Tue, 13 Jun 2023 21:07:16 +0100
From:   Mark Brown <broonie@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Mark Brown <broonie@...nel.org>
Subject: [PATCH] regmap: Check for register readability before checking
 cache during read

Ensure that we don't return a spurious cache hit for unreadable registers
(eg, with the flat cache which doesn't understand sparseness) by checking
for readability before we do a cache lookup.

Signed-off-by: Mark Brown <broonie@...nel.org>
---
 drivers/base/regmap/regmap.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index fa2d3fba6ac9..3efbe59ca1a7 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -2897,6 +2897,9 @@ static int _regmap_read(struct regmap *map, unsigned int reg,
 	int ret;
 	void *context = _regmap_map_get_context(map);
 
+	if (!regmap_readable(map, reg))
+		return -EIO;
+
 	if (!map->cache_bypass) {
 		ret = regcache_read(map, reg, val);
 		if (ret == 0)
@@ -2906,9 +2909,6 @@ static int _regmap_read(struct regmap *map, unsigned int reg,
 	if (map->cache_only)
 		return -EBUSY;
 
-	if (!regmap_readable(map, reg))
-		return -EIO;
-
 	ret = map->reg_read(context, reg, val);
 	if (ret == 0) {
 		if (regmap_should_log(map))

---
base-commit: 858fd168a95c5b9669aac8db6c14a9aeab446375
change-id: 20230613-b4-regmap-check-readability-before-cache-9f658338a5c1

Best regards,
-- 
Mark Brown <broonie@...nel.org>