linux-kernel - Re: [PATCH 1/3] cap1106: Add support for various cap11xx devices

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Date:	Sun, 21 Sep 2014 12:53:33 +0200
From:	Daniel Mack <daniel@...que.org>
To:	Matt Ranostay <mranostay@...il.com>, galak@...eaurora.org,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	dmitry.torokhov@...il.com, robh+dt@...nel.org
CC:	devicetree@...r.kernel.org
Subject: Re: [PATCH 1/3] cap1106: Add support for various cap11xx devices

Hi,

On 09/21/2014 05:01 AM, Matt Ranostay wrote:
>  	priv->regmap = devm_regmap_init_i2c(i2c_client, &cap1106_regmap_config);
>  	if (IS_ERR(priv->regmap))
>  		return PTR_ERR(priv->regmap);
>  
> -	error = regmap_read(priv->regmap, CAP1106_REG_PRODUCT_ID, &val);
> -	if (error)
> -		return error;
> -
> -	if (val != CAP1106_PRODUCT_ID) {
> -		dev_err(dev, "Product ID: Got 0x%02x, expected 0x%02x\n",
> -			val, CAP1106_PRODUCT_ID);
> -		return -ENODEV;
> -	}
> -

Btw - the purpose of this code was to detect board configuration
mismatch. After all, I2C lacks a way to properly identify peripherals,
so the more runtime checks we do at probe time, the more of a chance we
have to detect wrong setups. This device is actually well implemented
and tells us something about itself.

Hence, I'd propose to define a structure like this:

struct cap11xx_hw_model {
	uint8_t product_id;
	unsigned int num_channels;
};

... and attach instances of that to the members of cap1106_dt_ids[] and
cap1106_i2c_ids[]. In the probe function, check that the contents of
CAP1106_PRODUCT_ID match what is expected by the configured model.

Thanks,
Daniel

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