linux-kernel - Re: [PATCH v2 01/12] drm/i915/dp: convert to struct drm

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Date:   Tue, 11 Feb 2020 16:03:31 +0200
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Wambui Karuga <wambui.karugax@...il.com>,
        joonas.lahtinen@...ux.intel.com, rodrigo.vivi@...el.com,
        airlied@...ux.ie, daniel@...ll.ch
Cc:     sean@...rly.run, intel-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 01/12] drm/i915/dp: convert to struct drm_device based logging macros.

On Thu, 06 Feb 2020, Wambui Karuga <wambui.karugax@...il.com> wrote:
> @@ -5990,11 +6040,13 @@ int intel_dp_hdcp_write_an_aksv(struct intel_digital_port *intel_dig_port,
>  static int intel_dp_hdcp_read_bksv(struct intel_digital_port *intel_dig_port,
>  				   u8 *bksv)
>  {
> +	struct intel_dp *intel_dp = &intel_dig_port->dp;
>  	ssize_t ret;
>  	ret = drm_dp_dpcd_read(&intel_dig_port->dp.aux, DP_AUX_HDCP_BKSV, bksv,
>  			       DRM_HDCP_KSV_LEN);
>  	if (ret != DRM_HDCP_KSV_LEN) {
> -		DRM_DEBUG_KMS("Read Bksv from DP/AUX failed (%zd)\n", ret);
> +		drm_dbg_kms(&dp_to_i915(intel_dp)->drm,
> +			    "Read Bksv from DP/AUX failed (%zd)\n", ret);
>  		return ret >= 0 ? -EIO : ret;
>  	}

If you're introducing local variables just for logging, I would prefer
it to be i915.

	struct drm_i915_private *i915 = to_i915(intel_dig_port->base.base.dev);

	...

	drm_dbg_kms(&i915->drm, ...);

If you look at dp_to_i915() it actually converts intel_dp back to
intel_digital_port, and then does the above to it, to get at i915. This
is an unnecessary dance.

It's fine to use &dp_to_i915(intel_dp)->drm when there are only a couple
of logging calls in a function, and intel_dp is already there. But any
more than that, and I'd add the i915 local variable. For example, but
not limited to, intel_dp_handle_test_request() would benefit from i915
local var.

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Graphics Center