A common method of probing an i2c bus is trying to do a zero-length write. Handle this case by checking the length first before decrementing it.
This is actually important, since attempting a zero-length write 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 | 7 ++++--- 1 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index c12db72..99a04f8 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -248,9 +248,10 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg, u32 val, loop;
val = loop = 0; - do { - val |= *buf++ << (8 * loop); - } while (--len && ++loop < 4); + while (len && loop < 4) { + val |= *buf++ << (8 * loop++); + len -= 1; + }
I915_WRITE(GMBUS3 + reg_offset, val); I915_WRITE(GMBUS1 + reg_offset,