linux-kernel - Re: [PATCH RFC 0/2] Add Renesas RPC-IF support

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Message-ID: <0af05149-78f5-8639-4a23-84edda0073ea@cogentembedded.com>
Date:   Wed, 11 Dec 2019 19:20:51 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Chris Brandt <Chris.Brandt@...esas.com>,
        Rob Herring <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Mason Yang <masonccyang@...c.com.tw>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>
Subject: Re: [PATCH RFC 0/2] Add Renesas RPC-IF support

On 12/11/2019 05:33 PM, Chris Brandt wrote:

>> Here's a set of 2 patches against Linus' repo. Renesas Reduced Pin Count
>> Interface (RPC-IF) allows a SPI flash or HyperFlash connected to the SoC to
>> be accessed via the external address space read mode or the manual mode.
> 
> Looking at this driver, all it is are APIs. Meaning another driver is 
> needed to sit in between the MTD layer and this HW driver layer.
> 
> In the driver that I did, if the "RPC" HW is going to be used to control
> a SPI Flash device, it registered a spi controller and then the MTD 
> layer could access the device

   Via the SPI-to-MTD sublayer for (at least) direct mapping -- grep for "dirmap"
in drivers/mtd/spi-nor/spi-nor.c...

> just like any other SPI controller driver. No
> additional drivers are needed.

   Then why do we have *struct* spi_controller_mem_ops? Do All drivers implement
such ops?

[...]

MBR, Sergei