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

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Message-ID: <87wnrfqjfr.fsf@intel.com>
Date:   Mon, 31 May 2021 13:36:08 +0300
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     "Leizhen \(ThunderTown\)" <thunder.leizhen@...wei.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 Fri, 28 May 2021, "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com> wrote:
> 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.

Yes, if the loop is abstracted to a separate function.

BR,
Jani.

>
>
>> 
>> 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;
>>>  }
>> 
>

-- 
Jani Nikula, Intel Open Source Graphics Center