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[79.139.237.54]) by smtp.googlemail.com with ESMTPSA id 80sm4401198ljf.85.2020.06.16.06.56.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 16 Jun 2020 06:56:42 -0700 (PDT) Subject: Re: [PATCH v7 1/6] of_graph: add of_graph_get_local_port() To: Laurent Pinchart Cc: Thierry Reding , Sam Ravnborg , Rob Herring , Frank Rowand , dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200614172234.8856-1-digetx@gmail.com> <20200614172234.8856-2-digetx@gmail.com> <20200616012111.GE1629@pendragon.ideasonboard.com> <20200616012513.GF1629@pendragon.ideasonboard.com> From: Dmitry Osipenko Message-ID: <8b7c6395-edd8-cecd-7004-e9f3f22d61f2@gmail.com> Date: Tue, 16 Jun 2020 16:56:41 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200616012513.GF1629@pendragon.ideasonboard.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 16.06.2020 04:25, Laurent Pinchart пишет: > On Tue, Jun 16, 2020 at 04:21:12AM +0300, Laurent Pinchart wrote: >> Hi Dmitry, >> >> Thank you for the patch. >> >> On Sun, Jun 14, 2020 at 08:22:29PM +0300, Dmitry Osipenko wrote: >>> In some case, like a DRM display code for example, it's useful to silently >>> check whether port node exists at all in a device-tree before proceeding >>> with parsing the graph. >>> >>> This patch adds of_graph_get_local_port() which returns pointer to a local >>> port node, or NULL if graph isn't specified in a device-tree for a given >>> device node. >>> >>> Reviewed-by: Rob Herring >>> Reviewed-by: Sam Ravnborg >>> Signed-off-by: Dmitry Osipenko >>> --- >>> drivers/of/property.c | 32 +++++++++++++++++++++++--------- >>> include/linux/of_graph.h | 7 +++++++ >>> 2 files changed, 30 insertions(+), 9 deletions(-) >>> >>> diff --git a/drivers/of/property.c b/drivers/of/property.c >>> index 1f2086f4e7ce..05c5f619b8bb 100644 >>> --- a/drivers/of/property.c >>> +++ b/drivers/of/property.c >>> @@ -608,15 +608,7 @@ struct device_node *of_graph_get_next_endpoint(const struct device_node *parent, >>> * parent port node. >>> */ >>> if (!prev) { >>> - struct device_node *node; >>> - >>> - node = of_get_child_by_name(parent, "ports"); >>> - if (node) >>> - parent = node; >>> - >>> - port = of_get_child_by_name(parent, "port"); >>> - of_node_put(node); >>> - >>> + port = of_graph_get_local_port(parent); >>> if (!port) { >>> pr_err("graph: no port node found in %pOF\n", parent); >>> return NULL; >>> @@ -765,6 +757,28 @@ struct device_node *of_graph_get_remote_port(const struct device_node *node) >>> } >>> EXPORT_SYMBOL(of_graph_get_remote_port); >>> >>> +/** >>> + * of_graph_get_local_port() - get local port node >>> + * @node: pointer to a local endpoint device_node >>> + * >>> + * Return: First local port node associated with local endpoint node linked >>> + * to @node. Use of_node_put() on it when done. >>> + */ >>> +struct device_node *of_graph_get_local_port(const struct device_node *node) > > I forgot to mention that, given that there could be multiple 'port' > nodes, this function would be better named > of_graph_get_first_local_port(). 'first' here would refer to the nodes > order in the device tree, which I believe may not match the port number. > For instance, in the following case > > ports { > #address-cells = <1>; > #size-cells = <1>; > port@1 { > reg = <1>; > }; > port@0 { > reg = <0>; > }; > }; > > the function would I believe return port@1. It may be a good idea to > explain this in the documentation. Hello Laurent, It's correct that the port@1 will be returned in yours example. I'll improve the doc and the function's name in the next revision, thank you for the suggestions! > Depending on how you use this > function, if your only use case is to test for the presence of port > nodes, it may be best to return a bool and name it of_graph_has_port() > or something similar. > >>> +{ >>> + struct device_node *ports, *port; >>> + >>> + ports = of_get_child_by_name(node, "ports"); >>> + if (ports) >>> + node = ports; >>> + >>> + port = of_get_child_by_name(node, "port"); >>> + of_node_put(ports); >>> + >>> + return port; >> >> The implementation doesn't seem to match the documentation. If node is a >> pointer to an endpoint, it should not have any ports child. Right, I'll reword the doc in v8. This function doesn't differentiate between start / end points. It's up to a user of this function to check whether node is endpoint or something else if needed. Thank you very much for the comments!