tpm/tpm_i2c_atmel: Return -E2BIG when the transfer is incomplete

BugLink: https://bugs.launchpad.net/bugs/1828420

commit 442601e8 upstream

Return -E2BIG when the transfer is incomplete. The upper layer does
not retry, so not doing that is incorrect behaviour.

Cc: stable@vger.kernel.org
Fixes: a2871c62 ("tpm: Add support for Atmel I2C TPMs")
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

drivers/char/tpm/tpm_i2c_atmel.c

@@ -65,7 +65,15 @@ static int i2c_atmel_send(struct tpm_chip *chip, u8 *buf, size_t len)
 	dev_dbg(&chip->dev,
 		"%s(buf=%*ph len=%0zx) -> sts=%d\n", __func__,
 		(int)min_t(size_t, 64, len), buf, len, status);
-	return status;
+
+	if (status < 0)
+		return status;
+
+	/* The upper layer does not support incomplete sends. */
+	if (status != len)
+		return -E2BIG;
+
+	return 0;
 }
 
 static int i2c_atmel_recv(struct tpm_chip *chip, u8 *buf, size_t count)