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@xxxxxxxxxxxx>
---
drivers/gpu/drm/i915/intel_i2c.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index c12db72..5a94e9b 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 {
+ while (len && loop < 4) {
val |= *buf++ << (8 * loop);
- } while (--len && ++loop < 4);
+ len -= 1;
+ }
I915_WRITE(GMBUS3 + reg_offset, val);
I915_WRITE(GMBUS1 + reg_offset,
--
1.7.7.3
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