[PATCH AUTOSEL 6.19-6.1] ASoC: sunxi: sun50i-dmic: Add missing check for devm_regmap_init_mmio

[Sasha Levin <sashal@kernel.org>]

From: Chen Ni <nichen@iscas.ac.cn>

[ Upstream commit 74823db9ba2e13f3ec007b354759b3d8125e462c ]

Add check for the return value of devm_regmap_init_mmio() and return the
error if it fails in order to catch the error.

Signed-off-by: Chen Ni <nichen@iscas.ac.cn>
Link: https://patch.msgid.link/20260127033250.2044608-1-nichen@iscas.ac.cn
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

## Analysis

### Commit Message Analysis

The commit adds a missing error check for `devm_regmap_init_mmio()` in
the sun50i-dmic audio driver's probe function. The message is
straightforward - it's adding a return value check that was missing.

### Code Change Analysis

The change is a 3-line addition:
```c
if (IS_ERR(host->regmap))
    return dev_err_probe(&pdev->dev, PTR_ERR(host->regmap),
                         "failed to initialise regmap\n");
```

This is inserted right after `devm_regmap_init_mmio()` returns into
`host->regmap`. Without this check, if `devm_regmap_init_mmio()` fails,
`host->regmap` will contain an ERR_PTR value. The driver then continues
execution and eventually uses this regmap pointer in subsequent
operations (regmap reads/writes), which would cause a NULL pointer
dereference or other crash since the ERR_PTR would be interpreted as a
valid pointer.

### Bug Mechanism

If `devm_regmap_init_mmio()` fails (e.g., memory allocation failure
inside regmap), the error pointer gets stored in `host->regmap`. Later,
when the driver tries to use regmap APIs with this invalid pointer, it
will crash. This is a real bug - a missing error check that leads to use
of an error pointer as a valid pointer.

### Severity Assessment

- **Trigger**: `devm_regmap_init_mmio()` would need to fail, which is
  uncommon but possible (memory pressure, internal regmap errors)
- **Consequence**: Kernel crash/oops when the invalid regmap pointer is
  subsequently used
- **Likelihood**: Low probability but non-zero, especially under memory
  pressure

### Stable Kernel Criteria

1. **Obviously correct and tested**: Yes - this follows the exact same
   pattern as all surrounding error checks in the same function. It's a
   textbook missing error check fix.
2. **Fixes a real bug**: Yes - missing error check on a function that
   can fail, leading to use of an ERR_PTR as a valid pointer.
3. **Important issue**: Moderate - it's a potential NULL deref/crash,
   though the trigger condition is uncommon.
4. **Small and contained**: Yes - 3 lines added, single file, no
   behavioral change on success path.
5. **No new features**: Correct - purely defensive error checking.
6. **Applies cleanly**: The change is self-contained with no
   dependencies.

### Risk Assessment

- **Risk**: Extremely low. The change only affects the error path. On
  the success path, behavior is identical.
- **Benefit**: Prevents a kernel crash if regmap initialization fails.
- **Pattern**: This is a very common type of stable fix - adding missing
  error checks in driver probe functions.

### Concerns

This is a fairly minor fix for an uncommon failure path in a specific
ARM SoC audio driver. The user base is limited to Allwinner sun50i
platforms. However, the fix is trivially correct, has zero risk of
regression, and prevents a real (if unlikely) crash.

### Decision

The fix is small, obviously correct, follows existing patterns in the
same function, prevents a potential crash from using an ERR_PTR, and has
essentially zero regression risk. It meets all stable kernel criteria.

**YES**

 sound/soc/sunxi/sun50i-dmic.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/soc/sunxi/sun50i-dmic.c b/sound/soc/sunxi/sun50i-dmic.c
index bab1e29c99887..eddfebe166169 100644
--- a/sound/soc/sunxi/sun50i-dmic.c
+++ b/sound/soc/sunxi/sun50i-dmic.c
@@ -358,6 +358,9 @@ static int sun50i_dmic_probe(struct platform_device *pdev)
 
 	host->regmap = devm_regmap_init_mmio(&pdev->dev, base,
 					     &sun50i_dmic_regmap_config);
+	if (IS_ERR(host->regmap))
+		return dev_err_probe(&pdev->dev, PTR_ERR(host->regmap),
+				     "failed to initialise regmap\n");
 
 	/* Clocks */
 	host->bus_clk = devm_clk_get(&pdev->dev, "bus");
-- 
2.51.0