[PATCH v2] mtd: hyperbus: add Renesas RPC-IF driver

[Behme Dirk (CM/ESO2)]

On 15.09.2020 07:27, Vignesh Raghavendra wrote:
> 
> 
> On 9/15/20 9:37 AM, Behme Dirk (CM/ESO2) wrote:
>>
>>
>> On 14.09.2020 15:09, Vignesh Raghavendra wrote:
>>> Hi Sergei,
>>>
>>> On 5/14/20 2:13 AM, Sergei Shtylyov wrote:
>>>> Add the HyperFLash driver for the Renesas RPC-IF.  It's the "front end"
>>>> driver using the "back end" APIs in the main driver to talk to the real
>>>> hardware.
>>>>
>>>> Signed-off-by: Sergei Shtylyov <sergei.shtylyov at cogentembedded.com>
> [...]
>>>>
>>>>
>>> [...]
>>>> --- /dev/null
>>>> +++ linux/drivers/mtd/hyperbus/rpc-if.c
>>>> @@ -0,0 +1,165 @@
>>>> +// SPDX-License-Identifier: GPL-2.0
>>>> +/*
>>>> + * Linux driver for RPC-IF HyperFlash
>>>> + *
>>>> + * Copyright (C) 2019-2020 Cogent Embedded, Inc.
>>>> + */
>>>> +
>>>> +#include <linux/err.h>
>>>> +#include <linux/kernel.h>
>>>> +#include <linux/module.h>
>>>> +#include <linux/mtd/hyperbus.h>
>>>> +#include <linux/mtd/mtd.h>
>>>> +#include <linux/mux/consumer.h>
>>>> +#include <linux/of.h>
>>>> +#include <linux/platform_device.h>
>>>> +#include <linux/types.h>
>>>> +
>>>> +#include <memory/renesas-rpc-if.h>
>>>> +
>>>> +/* FIXME: How to drop this? */
>>>> +#ifndef CONFIG_MTD_CFI_BE_BYTE_SWAP
>>>> +#error Enable config "Flash cmd/query data swapping (BIG_ENDIAN_BYTE)"
>>>> +#endif
>>>
>>> select MTD_CFI_BE_BYTE_SWAP in Kconfig does not help?
>>
>>
>> If I remember correctly 'select MTD_CFI_BE_BYTE_SWAP' in Kconfig doesn't
>> seem to work. Therefore the FIXME. I can't remember exactly the root
>> cause for that any more, but maybe it was the 'bool' type of
>> MTD_CFI_BE_BYTE_SWAP?
>>
> 
> Ah, sorry MTD_CFI_BE_BYTE_SWAP is a choice and select does not work on
> choice menus. how about:
> 
>> If anybody has a nice solution for that, it would be welcome :)
> 
> Does this work:
> 
>   config RPCIF_HYPERBUS
>          tristate "Renesas RPC-IF HyperBus driver"
>          depends on RENESAS_RPCIF
> -       select MTD_CFI_ADV_OPTIONS
> +       depends on MTD_CFI_BE_BYTE_SWAP || COMPILE_TEST
>          help
>            This option includes Renesas RPC-IF HyperFlash support.


Well, it at least makes the whole RPCIF_HYPERBUS option to vanish in 
case the (quite uncommon?) MTD_CFI_BE_BYTE_SWAP is not set, no? Or 
rephrased: How to make the potential user aware that 
MTD_CFI_BE_BYTE_SWAP needs to be enabled to make this option at least 
visible? From that point of view I feel the #error as given above more 
user friendly: RPCIF_HYPERBUS is there an can be enabled, but compiling 
is failing with a reasonable message if the dependencies are not met.

Best regards

Dirk