A common method of probing an i2c bus is trying to do a zero-length read. Handle this case by checking the length first waiting for data to be read.
This is actually important, since attempting a zero-length read is one of the ways that i2cdetect and i2c_new_probed_device detect whether there is device present on the bus with a given address.
Signed-off-by: Daniel Kurtz djkurtz@chromium.org --- drivers/gpu/drm/i915/intel_i2c.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index cab879f..e249160 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -217,7 +217,7 @@ gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg, (len << GMBUS_BYTE_COUNT_SHIFT) | (msg->addr << GMBUS_SLAVE_ADDR_SHIFT) | GMBUS_SLAVE_READ | GMBUS_SW_RDY); - do { + while (len) { int ret; u32 val, loop = 0; u32 gmbus2; @@ -235,7 +235,7 @@ gmbus_xfer_read(struct drm_i915_private *dev_priv, struct i2c_msg *msg, *buf++ = val & 0xff; val >>= 8; } while (--len && ++loop < 4); - } while (len); + }
return 0; }