linux-kernel - Re: [PATCH 1/1] drm/i915/hdcp: Simplify code in intel_hdcp_auth

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 28 May 2021 17:36:43 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        intel-gfx <intel-gfx@...ts.freedesktop.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] drm/i915/hdcp: Simplify code in
 intel_hdcp_auth_downstream()



On 2021/5/27 18:04, Jani Nikula wrote:
> On Thu, 27 May 2021, Zhen Lei <thunder.leizhen@...wei.com> wrote:
>> If intel_hdcp_validate_v_prime() has been successful within the allowed
>> number of tries, we can directly call drm_dbg_kms() and "goto out" without
>> jumping out of the loop and repeatedly judging whether the operation is
>> successful. This can help us reduce an unnecessary if judgment. And it's
>> a little clearer to read.
> 
> Generally I think the "happy day scenario" should be at the topmost
> indentation level and not buried in the ifs with a goto exit.

for (xxx) {
   if (a == b)
       return found;
}

At least this way of writing is common.


> 
> BR,
> Jani.
> 
>>
>> No functional change.
>>
>> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
>> ---
>>  drivers/gpu/drm/i915/display/intel_hdcp.c | 24 ++++++++++-------------
>>  1 file changed, 10 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
>> index d8570e14fe60..c32a854eda66 100644
>> --- a/drivers/gpu/drm/i915/display/intel_hdcp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
>> @@ -663,13 +663,13 @@ int intel_hdcp_auth_downstream(struct intel_connector *connector)
>>  
>>  	ret = shim->read_ksv_fifo(dig_port, num_downstream, ksv_fifo);
>>  	if (ret)
>> -		goto err;
>> +		goto out;
>>  
>>  	if (drm_hdcp_check_ksvs_revoked(&dev_priv->drm, ksv_fifo,
>>  					num_downstream) > 0) {
>>  		drm_err(&dev_priv->drm, "Revoked Ksv(s) in ksv_fifo\n");
>>  		ret = -EPERM;
>> -		goto err;
>> +		goto out;
>>  	}
>>  
>>  	/*
>> @@ -680,20 +680,16 @@ int intel_hdcp_auth_downstream(struct intel_connector *connector)
>>  		ret = intel_hdcp_validate_v_prime(connector, shim,
>>  						  ksv_fifo, num_downstream,
>>  						  bstatus);
>> -		if (!ret)
>> -			break;
>> -	}
>> -
>> -	if (i == tries) {
>> -		drm_dbg_kms(&dev_priv->drm,
>> -			    "V Prime validation failed.(%d)\n", ret);
>> -		goto err;
>> +		if (!ret) {
>> +			drm_dbg_kms(&dev_priv->drm,
>> +				    "HDCP is enabled (%d downstream devices)\n",
>> +				    num_downstream);
>> +			goto out;
>> +		}
>>  	}
>>  
>> -	drm_dbg_kms(&dev_priv->drm, "HDCP is enabled (%d downstream devices)\n",
>> -		    num_downstream);
>> -	ret = 0;
>> -err:
>> +	drm_dbg_kms(&dev_priv->drm, "V Prime validation failed.(%d)\n", ret);
>> +out:
>>  	kfree(ksv_fifo);
>>  	return ret;
>>  }
>