Subject: Re: [RFC] I2C: fsl-i2c: make device probing configurable via FDT

From: Jean Delvare <[email-masked]>
Date: Wed, 16 Jul 2008 14:05:11 +0200

Hi Wolfgang,

On Wed, 16 Jul 2008 12:47:25 +0200, Wolfgang Grandegger wrote:
> Currently, the I2C buses are probed for HWMON I2C devices, which might
> not be acceptable in same cases. This patch makes device probing
> configurable through the property "probe" of the FDT I2C device node:
> 
>        i2c@3000 {
>             ...
>             compatible = "fsl-i2c";
>             probe;
> 	    ...
>         };
> 
> Assuming that systems using fsl-i2c should have proper platform data,
> probing is disabled by default. Unfortunately, that's not the case and
> various DTS files would require to be updated.
> 
> There have already been some discussion on this subject with Jean
> under the following thread:
> 
>   http://ozlabs.org/pipermail/linuxppc-dev/2008-July/060008.html
> 
> Please comment.
> 
> Thanks,
> 
> Wolfgang.
> 
> Signed-off-by: Wolfgang Grandegger <[email-masked]>
> ---
>  arch/powerpc/sysdev/fsl_soc.c |    4 ++++
>  drivers/i2c/busses/i2c-mpc.c  |   17 ++++++++++++++---
>  include/linux/fsl_devices.h   |    1 +
>  3 files changed, 19 insertions(+), 3 deletions(-)
> 
> Index: linux-2.6-denx/drivers/i2c/busses/i2c-mpc.c
> ===================================================================
> --- linux-2.6-denx.orig/drivers/i2c/busses/i2c-mpc.c
> +++ linux-2.6-denx/drivers/i2c/busses/i2c-mpc.c
> @@ -306,13 +306,21 @@ static const struct i2c_algorithm mpc_al
>  	.functionality = mpc_functionality,
>  };
>  
> -static struct i2c_adapter mpc_ops = {
> +static struct i2c_adapter mpc_probe_ops = {
>  	.owner = THIS_MODULE,
>  	.name = "MPC adapter",
>  	.id = I2C_HW_MPC107,
>  	.algo = &mpc_algo,
>  	.class = I2C_CLASS_HWMON,
> -	.timeout = 1,
> + 	.timeout = 1,

Your patch is adding undesirable leading white space.

> +};
> +
> +static struct i2c_adapter mpc_ops = {
> +	.owner = THIS_MODULE,
> +	.name = "MPC adapter",
> +	.id = I2C_HW_MPC107,
> +	.algo = &mpc_algo,
> + 	.timeout = 1,
>  };

I don't think you need 2 separate structures. Just set the class field
at runtime (see below.)

>  
>  static int fsl_i2c_probe(struct platform_device *pdev)
> @@ -354,7 +362,10 @@ static int fsl_i2c_probe(struct platform
>  	mpc_i2c_setclock(i2c);
>  	platform_set_drvdata(pdev, i2c);
>  
> -	i2c->adap = mpc_ops;
> +	(i2c->flags & FSL_I2C_DEV_PROBE)

Missing if? :)

> +		i2c->adap = mpc_probe_ops;
> +	else
> +		i2c->adap = mpc_ops;

Or just:

	i2c->adap = mpc_ops;
	if (i2c->flags & FSL_I2C_DEV_PROBE)
		i2c->adap.flags = I2C_CLASS_HWMON;

>  	i2c->adap.nr = pdev->id;
>  	i2c_set_adapdata(&i2c->adap, i2c);
>  	i2c->adap.dev.parent = &pdev->dev;
> Index: linux-2.6-denx/arch/powerpc/sysdev/fsl_soc.c
> ===================================================================
> --- linux-2.6-denx.orig/arch/powerpc/sysdev/fsl_soc.c
> +++ linux-2.6-denx/arch/powerpc/sysdev/fsl_soc.c
> @@ -518,6 +518,10 @@ static int __init fsl_i2c_of_init(void)
>  		if (flags)
>  			i2c_data.device_flags |= FSL_I2C_DEV_CLOCK_5200;
>  
> +		flags = of_get_property(np, "probe", NULL);
> +		if (flags)
> +			i2c_data.device_flags |= FSL_I2C_DEV_PROBE;
> +
>  		ret =
>  		    platform_device_add_data(i2c_dev, &i2c_data,
>  					     sizeof(struct
> Index: linux-2.6-denx/include/linux/fsl_devices.h
> ===================================================================
> --- linux-2.6-denx.orig/include/linux/fsl_devices.h
> +++ linux-2.6-denx/include/linux/fsl_devices.h
> @@ -82,6 +82,7 @@ struct fsl_i2c_platform_data {
>  /* Flags related to I2C device features */
>  #define FSL_I2C_DEV_SEPARATE_DFSRR	0x00000001
>  #define FSL_I2C_DEV_CLOCK_5200		0x00000002
> +#define FSL_I2C_DEV_PROBE		0x00000004
>  
>  enum fsl_usb2_operating_modes {
>  	FSL_USB2_MPH_HOST,

As a side note: in general it is not a good idea to use a template for
struct i2c_adapter. This structure is relatively large compared to the
few fields you need to set. If you insist on having a template, it
should at least be marked either const or __initdata.

-- 
Jean Delvare