[PATCH 4.14 215/217] i2c: core: ACPI: Properly set status byte to 0 for multi-byte writes

From: Greg Kroah-Hartman
Date: Thu Aug 23 2018 - 04:38:30 EST


4.14-stable review patch. If anyone has any objections, please let me know.

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

From: Hans de Goede <hdegoede@xxxxxxxxxx>

commit c463a158cb6c5d9a85b7d894cd4f8116e8bd6be0 upstream.

acpi_gsb_i2c_write_bytes() returns i2c_transfer()'s return value, which
is the number of transfers executed on success, so 1.

The ACPI code expects us to store 0 in gsb->status for success, not 1.

Specifically this breaks the following code in the Thinkpad 8 DSDT:

ECWR = I2CW = ECWR /* \_SB_.I2C1.BAT0.ECWR */
If ((ECST == Zero))
{
ECRD = I2CR /* \_SB_.I2C1.I2CR */
}

Before this commit we set ECST to 1, causing the read to never happen
breaking battery monitoring on the Thinkpad 8.

This commit makes acpi_gsb_i2c_write_bytes() return 0 when i2c_transfer()
returns 1, so the single write transfer completed successfully, and
makes it return -EIO on for other (unexpected) return values >= 0.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
Acked-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Signed-off-by: Wolfram Sang <wsa@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/i2c/i2c-core-acpi.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

--- a/drivers/i2c/i2c-core-acpi.c
+++ b/drivers/i2c/i2c-core-acpi.c
@@ -475,11 +475,16 @@ static int acpi_gsb_i2c_write_bytes(stru
msgs[0].buf = buffer;

ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
- if (ret < 0)
- dev_err(&client->adapter->dev, "i2c write failed\n");

kfree(buffer);
- return ret;
+
+ if (ret < 0) {
+ dev_err(&client->adapter->dev, "i2c write failed: %d\n", ret);
+ return ret;
+ }
+
+ /* 1 transfer must have completed successfully */
+ return (ret == 1) ? 0 : -EIO;
}

static acpi_status