linux-kernel - Re: [PATCH v3 3/4] memory: omap-gpmc: Use a compatible match table when checking for NAND controller

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Date:   Mon, 20 Dec 2021 13:51:07 +0200
From:   Roger Quadros <rogerq@...nel.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        tony@...mide.com
Cc:     robh@...nel.org, kishon@...com, nm@...com, vigneshr@...com,
        linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v3 3/4] memory: omap-gpmc: Use a compatible match table
 when checking for NAND controller



On 20/12/2021 13:05, Krzysztof Kozlowski wrote:
> On 20/12/2021 11:53, Roger Quadros wrote:
>>
>>
>> On 17/12/2021 17:21, Krzysztof Kozlowski wrote:
>>> On 17/12/2021 11:29, Roger Quadros wrote:
>>>> As more compatibles can be added to the GPMC NAND controller driver
>>>> use a compatible match table.
>>>>
>>>> Signed-off-by: Roger Quadros <rogerq@...nel.org>
>>>> ---
>>>>  drivers/memory/omap-gpmc.c                   | 8 +++++++-
>>>>  drivers/mtd/nand/raw/omap2.c                 | 2 +-
>>>>  include/linux/platform_data/mtd-nand-omap2.h | 5 +++++
>>>>  3 files changed, 13 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/memory/omap-gpmc.c b/drivers/memory/omap-gpmc.c
>>>> index 624153048182..814ddb45c13d 100644
>>>> --- a/drivers/memory/omap-gpmc.c
>>>> +++ b/drivers/memory/omap-gpmc.c
>>>> @@ -2091,6 +2091,7 @@ static int gpmc_probe_generic_child(struct platform_device *pdev,
>>>>  	u32 val;
>>>>  	struct gpio_desc *waitpin_desc = NULL;
>>>>  	struct gpmc_device *gpmc = platform_get_drvdata(pdev);
>>>> +	bool is_nand = false;
>>>>  
>>>>  	if (of_property_read_u32(child, "reg", &cs) < 0) {
>>>>  		dev_err(&pdev->dev, "%pOF has no 'reg' property\n",
>>>> @@ -2183,7 +2184,12 @@ static int gpmc_probe_generic_child(struct platform_device *pdev,
>>>>  		}
>>>>  	}
>>>>  
>>>> -	if (of_device_is_compatible(child, "ti,omap2-nand")) {
>>>> +#if defined(CONFIG_MTD_NAND_OMAP2)
>>>
>>> if (IS_ENABLED()) is preferred. If needed, you could make omap_nand_ids
>>> symbol visible always (so without ifdef around it), because extern
>>> structure should not have impact when not defined (if I recall
>>> correctly...).
>>>
>>>> +	if (of_match_node(omap_nand_ids, child))
>>>> +		is_nand = true;
>>>> +#endif
>>>> +
>>>> +	if (is_nand) {
>>>>  		/* NAND specific setup */
>>>>  		val = 8;
>>>>  		of_property_read_u32(child, "nand-bus-width", &val);
>>>> diff --git a/drivers/mtd/nand/raw/omap2.c b/drivers/mtd/nand/raw/omap2.c
>>>> index b26d4947af02..fff834ee726f 100644
>>>> --- a/drivers/mtd/nand/raw/omap2.c
>>>> +++ b/drivers/mtd/nand/raw/omap2.c
>>>> @@ -2352,7 +2352,7 @@ static int omap_nand_remove(struct platform_device *pdev)
>>>>  	return ret;
>>>>  }
>>>>  
>>>> -static const struct of_device_id omap_nand_ids[] = {
>>>> +const struct of_device_id omap_nand_ids[] = {
>>>>  	{ .compatible = "ti,omap2-nand", },
>>>>  	{},
>>>>  };
>>>
>>> I think OMAP2 NAND driver can be a module, so this should have
>>> EXPORT_SYMBOL.
>>
>> To make it work in all combinations (e.g. omap_gpmc built in and
>> nand/raw/omap2.c as module) I had to define omap_nand_ids table as static
>> in the linux/platform_data/mtd-nand-omap2.h header.
>>
>> EXPORT_SYMBOL will of course be not required there. ;)
>>
> Which case exactly does it require to be static in the header?

Maybe there is a better way to do it.
e.g. If omap_gpmc.c is built-in and nand/raw/omap2.c is not built or built as
a module, what better way we can use?

--
cheers,
-roger