linux-kernel - Re: [RFC PATCH v3 1/4] drm: Introduce generic probe function for component based masters.

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Date:	Mon, 9 Nov 2015 11:15:15 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Liviu Dudau <Liviu.Dudau@....com>
Cc:	David Airlie <airlied@...ux.ie>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Mark Yao <mark.yao@...k-chips.com>,
	Heiko Stuebner <heiko@...ech.de>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	linux-rockchip <linux-rockchip@...ts.infradead.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v3 1/4] drm: Introduce generic probe function for
 component based masters.

On Mon, Oct 19, 2015 at 04:07:47PM +0100, Liviu Dudau wrote:
> A lot of component based DRM drivers use a variant of the same code
> as the probe function. They bind the crtc ports in the first iteration
> and then scan through the child nodes and bind the encoders attached
> to the remote endpoints. Factor the common code into a separate
> function called drm_of_component_probe() in order to increase code
> reuse.

Sorry, I take back my Acked-by.

> +	/*
> +	 * Bind the crtc's ports first, so that drm_of_find_possible_crtcs()
> +	 * called from encoder's .bind callbacks works as expected
> +	 */
> +	for (i = 0; ; i++) {
> +		port = of_parse_phandle(dev->of_node, "ports", i);
> +		if (!port)
> +			break;
> +
> +		if (!of_device_is_available(port->parent)) {
> +			of_node_put(port);
> +			continue;
> +		}
> +
> +		component_match_add(dev, &match, compare_of, port);
> +		of_node_put(port);

We shouldn't be putting the ports here - we're still retaining a
reference against the port, even though it's by address.  Yes, we have
no way to release this reference, which probably ought to be fixed.
Please replace this of_node_put() here with a comment to that effect.

> +		for_each_child_of_node(port, ep) {
> +			remote = of_graph_get_remote_port_parent(ep);
> +			if (!remote || !of_device_is_available(remote)) {
> +				of_node_put(remote);
> +				continue;
> +			} else if (!of_device_is_available(remote->parent)) {
> +				dev_warn(dev, "parent device of %s is not available\n",
> +					 remote->full_name);
> +				of_node_put(remote);
> +				continue;
> +			}
> +
> +			component_match_add(dev, &match, compare_of, remote);
> +			of_node_put(remote);

Same here.

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