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drm/i915: Prevent zero length "index" write 

The hardware always writes one or two bytes in the index portion of
an indexed transfer. Make sure the message we send as the index
doesn't have a zero length.

Cc: stable@vger.kernel.org
Cc: Daniel Kurtz <djkurtz@chromium.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Sean Paul <seanpaul@chromium.org>
Fixes: 56f9eac054 ("drm/i915/intel_i2c: use INDEX cycles for i2c read transactions")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171123194157.25367-3-ville.syrjala@linux.intel.com
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
(cherry picked from commit bb9e0d4bca)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
zero-colors
Ville Syrjälä 2017-11-23 21:41:57 +02:00 committed by Joonas Lahtinen
parent ae5c631e60
commit 56350fb897
1 changed files with 2 additions and 1 deletions
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3
drivers/gpu/drm/i915/intel_i2c.c
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@ -439,7 +439,8 @@ gmbus_is_index_read(struct i2c_msg *msgs, int i, int num)
{
return (i + 1 < num &&
msgs[i].addr == msgs[i + 1].addr &&
!(msgs[i].flags & I2C_M_RD) && msgs[i].len <= 2 &&
!(msgs[i].flags & I2C_M_RD) &&
(msgs[i].len == 1 || msgs[i].len == 2) &&
(msgs[i + 1].flags & I2C_M_RD));
}