Re: [PATCH v2 1/2] i2c: core: ACPI: Properly set status byte to 0 for multi-byte writes

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 12-08-18 22:39, Peter Rosin wrote:
> On 2018-08-12 12:53, Hans de Goede wrote:
>> 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.
> 
> I'm wondering if this might be fallout from one of
> 35cd67a0caf7 ("i2c: viperboard: return message count on master_xfer success")
> de9a8634f1cb ("i2c: pmcmsp: return message count on master_xfer success")

No, these are using the designware driver, so these commits are not
the cause, this simply is a long standing bug.

Regards,

Hans