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

From: Wolfgang Grandegger <[email-masked]>
Date: Wed, 16 Jul 2008 15:03:19 +0200

Jean Delvare wrote:
> 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? :)

Oops, I obviously forgot the quilt refresh before sending.

> 
>> +		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;

Right, mpc_ops is not a pointer, as I realize now.

>>  	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.

Wolfgang.