linux-kernel - Re: [PATCH 2/3] tegra: pwm-backlight: add tegra pwm-bl driver

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Message-ID: <3208798.X7kqxH1FjQ@percival>
Date:	Wed, 23 Jan 2013 19:29:16 +0900
From:	Alex Courbot <acourbot@...dia.com>
To:	Leela Krishna Amudala <leelakrishna.a@...il.com>
CC:	Thierry Reding <thierry.reding@...onic-design.de>,
	Stephen Warren <swarren@...dotorg.org>,
	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Mark Zhang <markz@...dia.com>,
	"gnurou@...il.com" <gnurou@...il.com>
Subject: Re: [PATCH 2/3] tegra: pwm-backlight: add tegra pwm-bl driver

On Wednesday 23 January 2013 18:15:30 Leela Krishna Amudala wrote:
> > +       pwm_backlight_set_subdriver_data(dev, data);
> 
> Here you are passing ventana_bl_data pointer as input and in the
> pwm_backlight_get_subdriver_data() function you are assigning the
> received driver data to backlight_device pointer. As both are two
> different structures with different structure fields in it. There can
> be a chance for a crash.

That's because the following happens later in pwm_backlight_probe():

	pb->subdriver_data = dev_get_drvdata(&pdev->dev);
	...
	bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
				       &pwm_backlight_ops, &props);
	...
	platform_set_drvdata(pdev, bl);

So from then on the result of dev_get_drvdata() is indeed an instance of 
backlight_device from which we can retrieve the subdriver data. I'm not really 
proud of this. But fortunately it seems like we are going to do things 
differently.

Alex.

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