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From:   =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= 
        <u.kleine-koenig@pengutronix.de>
To:     Tudor Ambarus <tudor.ambarus@microchip.com>
Cc:     Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Nicolas Ferre <nicolas.ferre@microchip.com>,
        linux-crypto@vger.kernel.org, kernel@pengutronix.de,
        Claudiu Beznea <claudiu.beznea@microchip.com>,
        linux-arm-kernel@lists.infradead.org, linux-i2c@vger.kernel.org
Subject: [PATCH] crypto: atmel-ecc - Remove duplicated error reporting in .remove()
Date:   Fri, 20 May 2022 19:21:00 +0200
Message-Id: <20220520172100.773730-1-u.kleine-koenig@pengutronix.de>
In-Reply-To: <7ffd4d35-938a-3e82-b39b-92e76819fa92@microchip.com>
References: <7ffd4d35-938a-3e82-b39b-92e76819fa92@microchip.com>
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Returning an error value in an i2c remove callback results in an error
message being emitted by the i2c core, but otherwise it doesn't make a
difference. The device goes away anyhow and the devm cleanups are
called.

As atmel_ecc_remove() already emits an error message on failure and the
additional error message by the i2c core doesn't add any useful
information, change the return value to zero to suppress this message.

Also make the error message a bit more drastical because when the device
is still busy on remove, it's likely that it will access freed memory
soon.

This patch is a preparation for making i2c remove callbacks return void.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
 drivers/crypto/atmel-ecc.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/crypto/atmel-ecc.c b/drivers/crypto/atmel-ecc.c
index 333fbefbbccb..6ba38275de8c 100644
--- a/drivers/crypto/atmel-ecc.c
+++ b/drivers/crypto/atmel-ecc.c
@@ -349,8 +349,16 @@ static int atmel_ecc_remove(struct i2c_client *client)
 
 	/* Return EBUSY if i2c client already allocated. */
 	if (atomic_read(&i2c_priv->tfm_count)) {
-		dev_err(&client->dev, "Device is busy\n");
-		return -EBUSY;
+		/*
+		 * After we return here, the memory backing the device is freed.
+		 * That happens no matter what the return value of this function
+		 * is because in the Linux device model there is no error
+		 * handling for unbinding a driver.
+		 * If there is still some action pending, it probably involves
+		 * accessing the freed memory.
+		 */
+		dev_emerg(&client->dev, "Device is busy, expect memory corruption.\n");
+		return 0;
 	}
 
 	crypto_unregister_kpp(&atmel_ecdh_nist_p256);

base-commit: 3123109284176b1532874591f7c81f3837bbdc17
-- 
2.35.1