Commit 26883c31 authored by Daniel Kurtz's avatar Daniel Kurtz Committed by Daniel Vetter

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: default avatarDaniel Kurtz <djkurtz@chromium.org>
Reviewed-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
parent 3fdcf431
...@@ -248,9 +248,10 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg, ...@@ -248,9 +248,10 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg,
u32 val, loop; u32 val, loop;
val = loop = 0; val = loop = 0;
do { while (len && loop < 4) {
val |= *buf++ << (8 * loop); val |= *buf++ << (8 * loop++);
} while (--len && ++loop < 4); len -= 1;
}
I915_WRITE(GMBUS3 + reg_offset, val); I915_WRITE(GMBUS3 + reg_offset, val);
I915_WRITE(GMBUS1 + reg_offset, I915_WRITE(GMBUS1 + reg_offset,
......
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