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[79.139.237.54]) by smtp.googlemail.com with ESMTPSA id h24sm4411484lji.115.2020.06.16.07.14.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 16 Jun 2020 07:14:01 -0700 (PDT) Subject: Re: [PATCH v7 1/6] of_graph: add of_graph_get_local_port() From: Dmitry Osipenko 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> <8b7c6395-edd8-cecd-7004-e9f3f22d61f2@gmail.com> Message-ID: <7c40f145-f31b-8397-ac23-601828c9f013@gmail.com> Date: Tue, 16 Jun 2020 17:14:00 +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: <8b7c6395-edd8-cecd-7004-e9f3f22d61f2@gmail.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 16:56, Dmitry Osipenko пишет: > 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! > Although, I re-read the doc comment and compared it to the wording of the other of_graph_*() functions and it's already good as-is to me because the doc explicitly says the "Return: First local port associated with local endpoint...", which is exactly what this function does. But still the function name and it's brief description could be improved.