Re: [PATCH 2/8] drm/i915: Stop encryption for repeater with no sink

[Ramalingam C <ramalingam.c@intel.com>]

On Friday 02 February 2018 07:43 PM, Sean Paul wrote:
> On Fri, Feb 02, 2018 at 04:15:14PM +0530, Ramalingam C wrote:
>> If a HDCP repeater is detected with zero hdcp authenticated
>> downstream devices, there are two option as below:
>>
>> 1. Dont continue on second stage authentication. Disable encryption.
>> 2. Continue with second stage authentication excluding the KSV list and
>>     continue encryption on success.
>>
>> This patch adopts the option 1.
> It doesn't seem that hard to adopt option 2 and avoid failure. That would result
> in a better experience.
True. Not too much effort for option 2. But I am not seeing any ROI out 
of it at this point.
what is the benefit of encrypting if repeater cant use it, as it has 0 
sinks attached to it.
Still do we want option two?

-Ram
>
>> Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
>> ---
>>   drivers/gpu/drm/i915/intel_hdcp.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_hdcp.c b/drivers/gpu/drm/i915/intel_hdcp.c
>> index 0021511ae4d7..182a3c8a4e4a 100644
>> --- a/drivers/gpu/drm/i915/intel_hdcp.c
>> +++ b/drivers/gpu/drm/i915/intel_hdcp.c
>> @@ -175,10 +175,10 @@ int intel_hdcp_auth_downstream(struct intel_connector *connector)
>>   		return -EPERM;
>>   	}
>>   
>> -	/* If there are no downstream devices, we're all done. */
>> +	/* If there are no downstream devices, we're not encrypting. */
>>   	num_downstream = DRM_HDCP_NUM_DOWNSTREAM(bstatus[0]);
>>   	if (num_downstream == 0)
>> -		return 0;
>> +		return -EINVAL;
>>   
>>   	ksv_fifo = kzalloc(num_downstream * DRM_HDCP_KSV_LEN, GFP_KERNEL);
>>   	if (!ksv_fifo)
>> -- 
>> 2.7.4
>>

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