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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Hans de Goede <hdegoede@redhat.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Wolfram Sang <wsa@the-dreams.de>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.18 055/197] i2c: core: ACPI: Make acpi_gsb_i2c_read_bytes() check i2c_transfer return value
Date:   Thu, 13 Sep 2018 15:30:04 +0200
Message-Id: <20180913131843.728550783@linuxfoundation.org>
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4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hans de Goede <hdegoede@redhat.com>

[ Upstream commit 0a30446c0dca3483c384b54a431cc951e15f7e79 ]

Currently acpi_gsb_i2c_read_bytes() directly returns i2c_transfer's return
value. i2c_transfer returns a value < 0 on error and 2 (for 2 successfully
executed transfers) on success. But the ACPI code expects 0 on success, so
currently acpi_gsb_i2c_read_bytes()'s caller does:

        if (status > 0)
                status = 0;

This commit makes acpi_gsb_i2c_read_bytes() return a value which can be
directly consumed by the ACPI code, mirroring acpi_gsb_i2c_write_bytes(),
this commit also makes acpi_gsb_i2c_read_bytes() explitcly check that
i2c_transfer returns 2, rather then accepting any value > 0.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/i2c/i2c-core-acpi.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/i2c/i2c-core-acpi.c
+++ b/drivers/i2c/i2c-core-acpi.c
@@ -453,8 +453,12 @@ static int acpi_gsb_i2c_read_bytes(struc
 		else
 			dev_err(&client->adapter->dev, "i2c read %d bytes from client@%#x starting at reg %#x failed, error: %d\n",
 				data_len, client->addr, cmd, ret);
-	} else {
+	/* 2 transfers must have completed successfully */
+	} else if (ret == 2) {
 		memcpy(data, buffer, data_len);
+		ret = 0;
+	} else {
+		ret = -EIO;
 	}
 
 	kfree(buffer);
@@ -595,8 +599,6 @@ i2c_acpi_space_handler(u32 function, acp
 		if (action == ACPI_READ) {
 			status = acpi_gsb_i2c_read_bytes(client, command,
 					gsb->data, info->access_length);
-			if (status > 0)
-				status = 0;
 		} else {
 			status = acpi_gsb_i2c_write_bytes(client, command,
 					gsb->data, info->access_length);