linux-kernel - Re: [PATCH 5/5] mfd: sunxi-gpadc-mfd: probe sunxi-gpadc-ts driver

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Message-ID: <B06C774E-19BF-43B3-9CA6-8AB67A1D8678@jic23.retrosnub.co.uk>
Date:	Mon, 25 Jul 2016 11:08:27 +0100
From:	Jonathan Cameron <jic23@...23.retrosnub.co.uk>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Jonathan Cameron <jic23@...nel.org>
CC:	Quentin Schulz <quentin.schulz@...e-electrons.com>,
	knaack.h@....de, lars@...afoo.de, pmeerw@...erw.net, wens@...e.org,
	dmitry.torokhov@...il.com, lee.jones@...aro.org,
	antoine.tenart@...e-electrons.com,
	thomas.petazzoni@...e-electrons.com, linux-kernel@...r.kernel.org,
	linux-iio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-input@...r.kernel.org
Subject: Re: [PATCH 5/5] mfd: sunxi-gpadc-mfd: probe sunxi-gpadc-ts driver



On 25 July 2016 10:51:13 BST, Maxime Ripard <maxime.ripard@...e-electrons.com> wrote:
>Hi Jonathan,
>
>On Sun, Jul 24, 2016 at 12:26:56PM +0100, Jonathan Cameron wrote:
>> >> @@ -142,23 +159,45 @@ static int sunxi_gpadc_mfd_probe(struct
>platform_device *pdev)
>> >>  	}
>> >>  
>> >>  	if (of_device_is_compatible(pdev->dev.of_node,
>> >> -				    "allwinner,sun4i-a10-ts"))
>> >> -		ret = mfd_add_devices(sunxi_gpadc_mfd_dev->dev, 0,
>> >> -				      sun4i_gpadc_mfd_cells,
>> >> -				      ARRAY_SIZE(sun4i_gpadc_mfd_cells), NULL,
>> >> -				      0, NULL);
>> >> -	else if (of_device_is_compatible(pdev->dev.of_node,
>> >> -					 "allwinner,sun5i-a13-ts"))
>> >> -		ret = mfd_add_devices(sunxi_gpadc_mfd_dev->dev, 0,
>> >> -				      sun5i_gpadc_mfd_cells,
>> >> -				      ARRAY_SIZE(sun5i_gpadc_mfd_cells), NULL,
>> >> -				      0, NULL);
>> >> -	else if (of_device_is_compatible(pdev->dev.of_node,
>> >> -					 "allwinner,sun6i-a31-ts"))
>> >> -		ret = mfd_add_devices(sunxi_gpadc_mfd_dev->dev, 0,
>> >> -				      sun6i_gpadc_mfd_cells,
>> >> -				      ARRAY_SIZE(sun6i_gpadc_mfd_cells), NULL,
>> >> -				      0, NULL);
>> >> +				    "allwinner,sun4i-a10-ts")) {
>> >> +		if (of_property_read_bool(pdev->dev.of_node,
>> >> +					  "allwinner,ts-attached"))
>> >> +			ret = mfd_add_devices(sunxi_gpadc_mfd_dev->dev, 0,
>> >> +					      sun4i_gpadc_mfd_cells_ts,
>> >> +					      ARRAY_SIZE(sun4i_gpadc_mfd_cells_ts),
>> >> +					      NULL, 0, NULL);
>> >> +		else
>> >> +			ret = mfd_add_devices(sunxi_gpadc_mfd_dev->dev, 0,
>> >> +					      sun4i_gpadc_mfd_cells,
>> >> +					      ARRAY_SIZE(sun4i_gpadc_mfd_cells),
>> >> +					      NULL, 0, NULL);
>> >> +	} else if (of_device_is_compatible(pdev->dev.of_node,
>> >> +					 "allwinner,sun5i-a13-ts")) {
>> >> +		if (of_property_read_bool(pdev->dev.of_node,
>> >> +					  "allwinner,ts-attached"))
>> >> +			ret = mfd_add_devices(sunxi_gpadc_mfd_dev->dev, 0,
>> >> +					      sun5i_gpadc_mfd_cells_ts,
>> >> +					      ARRAY_SIZE(sun5i_gpadc_mfd_cells_ts),
>> >> +					      NULL, 0, NULL);
>> >> +		else
>> >> +			ret = mfd_add_devices(sunxi_gpadc_mfd_dev->dev, 0,
>> >> +					      sun5i_gpadc_mfd_cells,
>> >> +					      ARRAY_SIZE(sun5i_gpadc_mfd_cells),
>> >> +					      NULL, 0, NULL);
>> >> +	} else if (of_device_is_compatible(pdev->dev.of_node,
>> >> +					 "allwinner,sun6i-a31-ts")) {
>> >> +		if (of_property_read_bool(pdev->dev.of_node,
>> >> +					  "allwinner,ts-attached"))
>> >> +			ret = mfd_add_devices(sunxi_gpadc_mfd_dev->dev, 0,
>> >> +					      sun6i_gpadc_mfd_cells_ts,
>> >> +					      ARRAY_SIZE(sun6i_gpadc_mfd_cells_ts),
>> >> +					      NULL, 0, NULL);
>> >> +		else
>> >> +			ret = mfd_add_devices(sunxi_gpadc_mfd_dev->dev, 0,
>> >> +					      sun6i_gpadc_mfd_cells,
>> >> +					      ARRAY_SIZE(sun6i_gpadc_mfd_cells),
>> >> +					      NULL, 0, NULL);
>> >> +	}
>> > 
>> > Please don't use any of_device_is_compatible.
>> Hi Maxime,
>> 
>> Why?  (Just curious...)
>
>This is completely redundant. The compatible has already been looked
>up once to match the driver, and you can associate a void * pointer to
>any compatible you register in the of_device_id array.
>
>So you can just retrieve the compatible that probed you in the first
>place, and use it's private data pointer to store whatever you want,
>without the numerous (and expensive) calls to of_device_is_compatible.
>
>It's also easier to maintain in the long term, since you can simply
>add a new field to the structure you would register there, instead of
>keeping adding more conditions.
Fair enough, now I get what you mean.

Thanks,

Jonathan
>
>Maxime

-- 
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