Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH v2 06/29] mtd: Add support for reading MTD devices via the
 nvmem API
From:   Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
To:     Boris Brezillon <boris.brezillon@bootlin.com>
Cc:     Alban <albeu@free.fr>, Bartosz Golaszewski <brgl@bgdev.pl>,
        Jonathan Corbet <corbet@lwn.net>, Sekhar Nori <nsekhar@ti.com>,
        Kevin Hilman <khilman@kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        David Woodhouse <dwmw2@infradead.org>,
        Brian Norris <computersforpeace@gmail.com>,
        Marek Vasut <marek.vasut@gmail.com>,
        Richard Weinberger <richard@nod.at>,
        Grygorii Strashko <grygorii.strashko@ti.com>,
        "David S . Miller" <davem@davemloft.net>,
        Naren <naren.kernel@gmail.com>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Lukas Wunner <lukas@wunner.de>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>,
        Sven Van Asbroeck <svendev@arcx.com>,
        Paolo Abeni <pabeni@redhat.com>, Rob Herring <robh@kernel.org>,
        David Lechner <david@lechnology.com>,
        Andrew Lunn <andrew@lunn.ch>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-i2c@vger.kernel.org, linux-mtd@lists.infradead.org,
        linux-omap@vger.kernel.org, netdev@vger.kernel.org,
        Bartosz Golaszewski <bgolaszewski@baylibre.com>
References: <20180810080526.27207-1-brgl@bgdev.pl>
 <20180810080526.27207-7-brgl@bgdev.pl> <20180817182720.6a6e5e8e@bbrezillon>
 <20180819133106.0420df5f@tock> <20180819184609.6dcdbb9a@bbrezillon>
 <20180821005327.0d312a85@tock> <20180821074404.23aaeb6b@bbrezillon>
 <81407b4d-a02f-4085-f333-a96102bd96ce@linaro.org>
 <20180821133136.1fada1b6@bbrezillon>
 <6fb36da4-c985-6d6e-f9e1-572f5cd7609b@linaro.org>
Message-ID: <e4ea4614-4673-020c-641d-30c94e7b761a@linaro.org>
Date:   Tue, 21 Aug 2018 14:37:37 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.2.1
MIME-Version: 1.0
In-Reply-To: <6fb36da4-c985-6d6e-f9e1-572f5cd7609b@linaro.org>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 21/08/18 14:34, Srinivas Kandagatla wrote:
> 
> 
> On 21/08/18 12:31, Boris Brezillon wrote:
>>>     * struct nvmem_config - NVMEM device configuration
>>> @@ -58,6 +62,7 @@ struct nvmem_config {
>>>           bool                    root_only;
>>>           nvmem_reg_read_t        reg_read;
>>>           nvmem_reg_write_t       reg_write;
>>> +       nvmem_match_t           match;
>>>           int     size;
>>>           int     word_size;
>>>           int     stride;
>>>
>> That might work if nvmem cells are defined directly under the mtdnode.
> Layout should not matter! which is the purpose of this callback.
> 
> The only purpose of this callback is to tell nvmem core that the 
> node(nvmem cell) belongs to that provider or not, if it is then we 
> successfully found the provider. Its up to the provider on which layout 
> it describes nvmem cells. Additionally the provider can add additional 
> sanity checks in this match function to ensure that cell is correctly 
> represented.
> 
> 
>> If we go for this approach, I'd recommend replacing this ->match() hook
>> by ->is_nvmem_cell() and pass it the cell node instead of the nvmem
>> node, because what we're really after here is knowing which subnode is
>> an nvmem cell and which subnode is not.
> 
> I agree on passing cell node instead of its parent. Regarding basic 
> validating if its nvmem cell or not, we can check compatible string in 
> nvmem core if we decide to use "nvmem-cell" compatible.
> 
> Also just in case if you missed this, nvmem would not iterate the
Sorry !! i hit send button too quickly I guess.

What I meant to say here, is that nvmem core would not iterate the 
provider node in any case.

Only time it looks at the cell node is when a consumer requests for the 
cell.

--srini