linux-kernel - Re: [PATCH] MIPS: Alchemy: add missing platform_set_drvdata() in au1550nd

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Message-ID: <20131127033555.GY9468@ld-irv-0074.broadcom.com>
Date:	Tue, 26 Nov 2013 19:35:55 -0800
From:	Brian Norris <computersforpeace@...il.com>
To:	Jingoo Han <jg1.han@...sung.com>
Cc:	'Wei Yongjun' <weiyj.lk@...il.com>,
	'David Woodhouse' <dwmw2@...radead.org>,
	'Bill Pemberton' <wfp5p@...ginia.edu>,
	'Artem Bityutskiy' <artem.bityutskiy@...ux.intel.com>,
	'Wei Yongjun' <yongjun_wei@...ndmicro.com.cn>,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MIPS: Alchemy: add missing platform_set_drvdata() in
 au1550nd_probe()

Hi Jingoo,

On Wed, Nov 27, 2013 at 09:14:18AM +0900, Jingoo Han wrote:
> On Wednesday, November 27, 2013 8:50 AM, Brian Norris wrote:
> > On Mon, Nov 11, 2013 at 02:18:29PM +0800, Wei Yongjun wrote:
> > > From: Wei Yongjun <yongjun_wei@...ndmicro.com.cn>
> > >
> > > Add missing platform_set_drvdata() in au1550nd_probe(), otherwise
> > > calling platform_get_drvdata() in remove returns NULL.
> > 
> > An alternative solution: just allocate ctx with devm_kzalloc().Then you
> > don't have to kfree() it at all.
> 
> Even if devm_kzalloc() is used, missing platform_set_drvdata() will
> be still necessary.
> 
> static int au1550nd_remove(struct platform_device *pdev)
> {
> 	struct au1550nd_ctx *ctx = platform_get_drvdata(pdev);
> 	.....
> 
> 	nand_release(&ctx->info);
> 
> 'ctx' is still used. Also, in order to use 'ctx',
> platform_get_drvdata(pdev) should be called.

Ah, I overlooked that. Thanks. In that case, you still have to do
something like this patch, and devm_kzalloc() can be left for another
day (or not done at all).

> > 
> > I don't mind one solution over the other too much. Let me know which
> > you'd prefer.
> > 
> > > Signed-off-by: Wei Yongjun <yongjun_wei@...ndmicro.com.cn>
> > > ---
> > >  drivers/mtd/nand/au1550nd.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/mtd/nand/au1550nd.c b/drivers/mtd/nand/au1550nd.c
> > > index ae8dd7c..909b673 100644
> > > --- a/drivers/mtd/nand/au1550nd.c
> > > +++ b/drivers/mtd/nand/au1550nd.c
> > > @@ -480,6 +480,8 @@ static int au1550nd_probe(struct platform_device *pdev)
> > >
> > >  	mtd_device_register(&ctx->info, pd->parts, pd->num_parts);
> > >
> > > +	platform_set_drvdata(pdev, ctx);
> > > +
> > 
> > Personally, I'd choose to call platform_set_drvdata() earlier in the
> > probe routine (e.g., immediately after its allocation), in case we end
> > up calling platform_get_drvdata() from some sub-routine in the future.
> 
> Do you mean the following?
> But, most drivers calls platform_set_drvdata() later in the probe routine.

I wouldn't say "most." An unscientific survey seemed to show some
variation, with no clear pattern.

> static int au1550nd_probe(struct platform_device *pdev)
> {
>         struct au1550nd_platdata *pd;
>         struct au1550nd_ctx *ctx;
>         struct nand_chip *this;
>         struct resource *r;
>         int ret, cs;
> 
>         pd = dev_get_platdata(&pdev->dev);
>         if (!pd) {
>                 dev_err(&pdev->dev, "missing platform data\n");
>                 return -ENODEV;
>         }
> 
>         ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
>         if (!ctx) {
>                 dev_err(&pdev->dev, "no memory for NAND context\n");
>                 return -ENOMEM;
>         }
> 
> +	platform_set_drvdata(pdev, ctx);
> +

Yes, that looks better to me.

Brian
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