linux-kernel - [PATCH RESEND v2 4/7] regulator: mt6358: Fail probe on unknown chip ID

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Date:   Fri, 21 Jul 2023 16:28:56 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     Lee Jones <lee@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     Chen-Yu Tsai <wenst@...omium.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH RESEND v2 4/7] regulator: mt6358: Fail probe on unknown chip ID

The MT6358 and MT6366 PMICs, and likely many others from MediaTek, have
a chip ID register, making the chip semi-discoverable.

The driver currently supports two PMICs and expects to be probed on one
or the other. It does not account for incorrect mfd driver entries or
device trees. While these should not happen, if they do, it could be
catastrophic for the device. The driver should be sure the hardware is
what it expects.

Make the driver fail to probe if the chip ID presented is not a known
one.

Suggested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Fixes: f0e3c6261af1 ("regulator: mt6366: Add support for MT6366 regulator")
Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>
---
 drivers/regulator/mt6358-regulator.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/regulator/mt6358-regulator.c b/drivers/regulator/mt6358-regulator.c
index b9cda2210c33..a1eae45f5fee 100644
--- a/drivers/regulator/mt6358-regulator.c
+++ b/drivers/regulator/mt6358-regulator.c
@@ -676,12 +676,18 @@ static int mt6358_regulator_probe(struct platform_device *pdev)
 	const struct mt6358_regulator_info *mt6358_info;
 	int i, max_regulator, ret;
 
-	if (mt6397->chip_id == MT6366_CHIP_ID) {
-		max_regulator = MT6366_MAX_REGULATOR;
-		mt6358_info = mt6366_regulators;
-	} else {
+	switch (mt6397->chip_id) {
+	case MT6358_CHIP_ID:
 		max_regulator = MT6358_MAX_REGULATOR;
 		mt6358_info = mt6358_regulators;
+		break;
+	case MT6366_CHIP_ID:
+		max_regulator = MT6366_MAX_REGULATOR;
+		mt6358_info = mt6366_regulators;
+		break;
+	default:
+		dev_err(&pdev->dev, "unsupported chip ID: %d\n", mt6397->chip_id);
+		return -EINVAL;
 	}
 
 	ret = mt6358_sync_vcn33_setting(&pdev->dev);
-- 
2.41.0.487.g6d72f3e995-goog