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>
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@ -248,9 +248,10 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg,
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u32 val, loop;
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u32 val, loop;
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val = loop = 0;
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val = loop = 0;
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do {
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while (len && loop < 4) {
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val |= *buf++ << (8 * loop);
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val |= *buf++ << (8 * loop++);
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} while (--len && ++loop < 4);
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len -= 1;
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}
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I915_WRITE(GMBUS3 + reg_offset, val);
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I915_WRITE(GMBUS3 + reg_offset, val);
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I915_WRITE(GMBUS1 + reg_offset,
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I915_WRITE(GMBUS1 + reg_offset,
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