Commit 26883c31 authored Mar 30, 2012 by Daniel Kurtz Committed by Daniel Vetter Apr 12, 2012

drm/i915/intel_i2c: handle zero-length writes

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>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

parent 3fdcf431

drivers/gpu/drm/i915/intel_i2c.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -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,