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

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Message-ID: <691a7ace-f18c-157e-88d2-303213aa0ee8@canonical.com>
Date:   Mon, 20 Dec 2021 12:05:18 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Roger Quadros <rogerq@...nel.org>, 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 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?

Best regards,
Krzysztof