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drm/radeon: fix atom aux payload size check for writes (v2) 

The atom aux param interface only supports 4 bits for
the total write transfer size (header + payload).  This
limits us to 12 bytes of payload rather than 16.  Add a
check for this. Reads are not affected.

v2: switch to WARN_ON_ONCE

Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Alex Deucher 2015-02-20 11:51:38 -05:00
parent dbfb00c3e7
commit 94a47c49fe
1 changed files with 7 additions and 0 deletions
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7
drivers/gpu/drm/radeon/atombios_dp.c
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@ -178,6 +178,13 @@ radeon_dp_aux_transfer(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
switch (msg->request & ~DP_AUX_I2C_MOT) { switch (msg->request & ~DP_AUX_I2C_MOT) {
case DP_AUX_NATIVE_WRITE: case DP_AUX_NATIVE_WRITE:
case DP_AUX_I2C_WRITE: case DP_AUX_I2C_WRITE:
/* The atom implementation only supports writes with a max payload of
* 12 bytes since it uses 4 bits for the total count (header + payload)
* in the parameter space. The atom interface supports 16 byte
* payloads for reads. The hw itself supports up to 16 bytes of payload.
*/
if (WARN_ON_ONCE(msg->size > 12))
return -E2BIG;
/* tx_size needs to be 4 even for bare address packets since the atom /* tx_size needs to be 4 even for bare address packets since the atom
* table needs the info in tx_buf[3]. * table needs the info in tx_buf[3].
*/ */