[PATCH 3/4] firmware: samsung: acpm: Fix mailbox channel leak on probe error

[Tudor Ambarus]

Sashiko identified the leak at [1].

The ACPM driver allocates hardware mailbox channels using
`mbox_request_channel()` during `acpm_channels_init()`. However, the
driver lacked a `.remove` callback and did not free these channels on
subsequent error paths inside `acpm_probe()`.

Consequently, if a later step in the probe function failed (e.g.,
`platform_device_register_data()` returning an error), the mailbox
channels were permanently leaked. This prevented the driver from ever
successfully re-probing on a transient `-EPROBE_DEFER`.

Fix this by modifying `acpm_free_mbox_chans()` to match the `devres`
action signature and wrapping it with `devm_add_action_or_reset()`.
This hooks the channel cleanup directly into the device's managed
resource lifecycle, ensuring the channels are properly freed on probe
failures or driver unbind.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: a88927b534ba ("firmware: add Exynos ACPM protocol driver")
Closes: https://sashiko.dev/#/patchset/20260420-acpm-tmu-v3-0-3dc8e93f0b26%40linaro.org [1]
Signed-off-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxx>
---
 drivers/firmware/samsung/exynos-acpm.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/samsung/exynos-acpm.c b/drivers/firmware/samsung/exynos-acpm.c
index a9baed5762d5..896fbdc2700e 100644
--- a/drivers/firmware/samsung/exynos-acpm.c
+++ b/drivers/firmware/samsung/exynos-acpm.c
@@ -535,8 +535,9 @@ static int acpm_achan_alloc_cmds(struct acpm_chan *achan)
  * acpm_free_mbox_chans() - free mailbox channels.
  * @acpm:	pointer to driver data.
  */
-static void acpm_free_mbox_chans(struct acpm_info *acpm)
+static void acpm_free_mbox_chans(void *data)
 {
+	struct acpm_info *acpm = data;
 	int i;
 
 	for (i = 0; i < acpm->num_chans; i++)
@@ -658,6 +659,10 @@ static int acpm_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	ret = devm_add_action_or_reset(dev, acpm_free_mbox_chans, acpm);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to add mbox free action.\n");
+
 	acpm_setup_ops(acpm);
 
 	platform_set_drvdata(pdev, acpm);

-- 
2.54.0.545.g6539524ca2-goog