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Thu, 14 May 2020 08:27:10 -0400 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3B2B6C061A0C; Thu, 14 May 2020 05:27:10 -0700 (PDT) Received: from [192.168.0.20] (cpc89242-aztw30-2-0-cust488.18-1.cable.virginm.net [86.31.129.233]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 14BE6259; Thu, 14 May 2020 14:27:06 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1589459228; bh=btE1eVa9M+PTyTG0zSQKjBum77rELHGcyKNXhLNO7+E=; h=Reply-To:Subject:To:Cc:References:From:Date:In-Reply-To:From; b=A8VlOmA/MqAVrQ0L6KdEaU1bkZCWiNuwBlKFsnO1DtgH9kw8dEhjQn2WvBhHk14m1 Vf1NbZtDZ/AUIPj0q4Qh9jV8nMGkPl6iX+o8QubH9ta6KE55mbfxVMf/DXhIQ+BXpk qlVjp0/4RbR5V7hZTe/wiYl207CMGNcETqlsvQwQ= Reply-To: kieran.bingham@ideasonboard.com Subject: Re: [PATCH v9 2/4] media: i2c: Add MAX9286 driver To: kieran.bingham+renesas@ideasonboard.com, Manivannan Sadhasivam Cc: linux-renesas-soc@vger.kernel.org, linux-media@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Mauro Carvalho Chehab , Laurent Pinchart , Jacopo Mondi , =?UTF-8?Q?Niklas_S=c3=b6derlund?= , sakari.ailus@iki.fi, Hans Verkuil , Hyun Kwon , Rob Herring , Jacopo Mondi , Laurent Pinchart , =?UTF-8?Q?Niklas_S=c3=b6derlund?= References: <20200512155105.1068064-1-kieran.bingham+renesas@ideasonboard.com> <20200512155105.1068064-3-kieran.bingham+renesas@ideasonboard.com> <20200512181706.GA21014@Mani-XPS-13-9360> <11aca587-9438-4fba-081c-b82631e96989@ideasonboard.com> <20200514101356.GF2877@Mani-XPS-13-9360> From: Kieran Bingham Autocrypt: addr=kieran.bingham@ideasonboard.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mani, On 14/05/2020 12:47, Kieran Bingham wrote: > On 14/05/2020 11:13, Manivannan Sadhasivam wrote: >> Hi Kieran, >>>>> +static int max9286_parse_dt(struct max9286_priv *priv) >>>>> +{ >>>>> + struct device *dev = &priv->client->dev; >>>>> + struct device_node *i2c_mux; >>>>> + struct device_node *node = NULL; >>>>> + unsigned int i2c_mux_mask = 0; >>>>> + >>>>> + of_node_get(dev->of_node); >>>> >>>> Why this is needed? >>> >>> Hrm .. I recall adding it to solve dt reference balancing. >>> >>> I wish I'd added a comment at the time ... as I can't recall the details >>> now. >>> >> >> I understand that it is for the refcount balancing but I certainly don't see >> a need for it. > > I'll go through and try to validate this again now. Aha, that's why: * of_find_node_by_name - Find a node by its "name" property * @from: The node to start searching from or NULL; the node * you pass will not be searched, only the next one * will. Typically, you pass what the previous call * returned. of_node_put() will be called on @from. * @name: The name string to match against I'll add a comment to state that it is to balance the of_node_put during of_find_node_by_name(). -- Kieran >>>>> + i2c_mux = of_find_node_by_name(dev->of_node, "i2c-mux"); >>>>> + if (!i2c_mux) { >>>>> + dev_err(dev, "Failed to find i2c-mux node\n"); >>>>> + of_node_put(dev->of_node); >>>>> + return -EINVAL; >>>>> + } >>>>> + >> [...] >>>> -- Regards -- Kieran