Return -ENXIO if a device NAKs a transaction.

Note: We should return -ETIMEDOUT, too if the transaction times out,
however, that error path is currently handled by the 'bit-bang fallback'.

Signed-off-by: Daniel Kurtz <djkurtz at chromium.org>
---
 drivers/gpu/drm/i915/intel_i2c.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index b97392c..2cdd531 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -243,6 +243,7 @@ gmbus_xfer(struct i2c_adapter *adapter,
                                               adapter);
        struct drm_i915_private *dev_priv = adapter->algo_data;
        int i, reg_offset;
+       int ret = 0;

        if (bus->force_bit)
                return intel_i2c_quirk_xfer(dev_priv, bus->force_bit, msgs,
@@ -333,6 +334,7 @@ clear_err:
         */
        I915_WRITE(GMBUS1 + reg_offset, GMBUS_SW_CLR_INT);
        I915_WRITE(GMBUS1 + reg_offset, 0);
+       ret = -ENXIO;

 done:
        /* Mark the GMBUS interface as disabled. We will re-enable it at the
@@ -342,7 +344,7 @@ done:

        mutex_unlock(&dev_priv->gmbus_mutex);

-       return i;
+       return ret ?: i;

 timeout:
        DRM_INFO("GMBUS timed out, falling back to bit banging on pin %d 
[%s]\n",
-- 
1.7.7.3

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