linux-kernel - Re: [PATCH v3 1/6] memory: omap-gpmc: Store handle to GPMC dev

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Date:	Thu, 10 Mar 2016 07:40:02 -0600
From:	"Franklin S Cooper Jr." <fcooper@...com>
To:	Roger Quadros <rogerq@...com>, <nsekhar@...com>,
	<dwmw2@...radead.org>, <computersforpeace@...il.com>,
	<tony@...mide.com>, <devicetree@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <linux-mtd@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/6] memory: omap-gpmc: Store handle to GPMC dev



On 03/10/2016 06:40 AM, Roger Quadros wrote:
> Franklin,
>
> On 10/03/16 06:07, Franklin S Cooper Jr wrote:
>> The dma channel information is located within the GPMC node. The NAND
>> driver requires a handle to the GPMC's dev to properly parse the DMA
>> properties. Therefore, store a handle to the dev so it can be referenced
>> within the NAND driver.
>>
>> Signed-off-by: Franklin S Cooper Jr <fcooper@...com>
>> ---
>>  drivers/memory/omap-gpmc.c                   | 1 +
>>  include/linux/platform_data/mtd-nand-omap2.h | 2 ++
>>  2 files changed, 3 insertions(+)
>>
>> diff --git a/drivers/memory/omap-gpmc.c b/drivers/memory/omap-gpmc.c
>> index 6515dfc..2932d13 100644
>> --- a/drivers/memory/omap-gpmc.c
>> +++ b/drivers/memory/omap-gpmc.c
>> @@ -1796,6 +1796,7 @@ static int gpmc_probe_nand_child(struct platform_device *pdev,
>>  
>>  	gpmc_nand_data->cs = val;
>>  	gpmc_nand_data->of_node = child;
>> +	gpmc_nand_data->gpmc_dev = &pdev->dev;
>>  
>>  	/* Detect availability of ELM module */
>>  	gpmc_nand_data->elm_of_node = of_parse_phandle(child, "ti,elm-id", 0);
>> diff --git a/include/linux/platform_data/mtd-nand-omap2.h b/include/linux/platform_data/mtd-nand-omap2.h
>> index 090bbab..534b984 100644
>> --- a/include/linux/platform_data/mtd-nand-omap2.h
>> +++ b/include/linux/platform_data/mtd-nand-omap2.h
>> @@ -80,5 +80,7 @@ struct omap_nand_platform_data {
>>  	/* for passing the partitions */
>>  	struct device_node	*of_node;
>>  	struct device_node	*elm_of_node;
>> +
>> +	struct device		*gpmc_dev;
>>  };
>>  #endif
>>
> Why do you need this? Can't we just use dev->parent in the omap2-nand driver?

The omap2-nand platform_device is created by
platform_device_alloc. The created platform_device dev
parent isn't by default set to the GPMC dev. I didn't think
this was the right approach to manually set the parent
property. However, taking a look at other usages of
platform_device_alloc it seems this is actually pretty
common. If your ok with this then I can go that route.
>
> cheers,
> -roger