[lm-sensors] Re: [PATCH 4/5] add i2c_probe_device and i2c_remove_device

Jean Delvare khali at linux-fr.org
Tue Aug 16 00:14:13 CEST 2005


Hi Nathan,

> These functions can be used for special-purpose adapters, such as
> those on TV tuner cards, where we generally know in advance what
> devices are attached.  This is important in cases where the adapter
> does not support probing or when probing is potentially dangerous to
> the connected devices.

Do you know of any adapter actually not supporting the SMBus Quick
command (which we use for probing)?

> --- linux-2.6.13-rc6+gregkh.orig/drivers/i2c/i2c-core.c
> +++ linux-2.6.13-rc6+gregkh/drivers/i2c/i2c-core.c
> @@ -671,6 +671,75 @@ int i2c_control(struct i2c_client *clien
>  }
>  
>  /* ----------------------------------------------------
> + * direct add/remove functions to avoid probing
> + * ----------------------------------------------------
> + */
> +
> +int i2c_probe_device(struct i2c_adapter *adapter, int driver_id,
> +		     int addr, int kind)
> +{
> +	struct list_head   *item;
> +	struct i2c_driver  *driver = NULL;
> +
> +	/* There's no way to probe addresses on this adapter... */
> +	if (kind < 0 && !i2c_check_functionality(adapter,I2C_FUNC_SMBUS_QUICK))
> +		return -EINVAL;

Coding style please: one space after the comma. 

> +
> +	down(&core_lists);
> +	list_for_each(item,&drivers) {

Ditto.

> +		driver = list_entry(item, struct i2c_driver, list);
> +		if (driver->id == driver_id)
> +			break;
> +	}
> +	up(&core_lists);
> +	if (!item)
> +		return -ENOENT;
> +
> +	/* Already in use? */
> +	if (i2c_check_addr(adapter, addr))
> +		return -EBUSY;
> +
> +	/* Make sure there is something at this address, unless forced */
> +	if (kind < 0) {
> +		if (i2c_smbus_xfer(adapter, addr, 0, 0, 0,
> +				   I2C_SMBUS_QUICK, NULL) < 0)
> +			return -ENODEV;
> +
> +		/* prevent 24RF08 corruption */
> +		if ((addr & ~0x0f) == 0x50)
> +			i2c_smbus_xfer(adapter, addr, 0, 0, 0,
> +				       I2C_SMBUS_QUICK, NULL);
> +	}
> +
> +	return driver->detect_client(adapter, addr, kind);
> +}

You are duplicating a part of i2c_probe_address() here. Why don't you
simply call it?

This part of the code is very sensible because of the 24RF08 corruption
issue. I have plans to change the probing method, e.g. by using SMBus
Receive Byte instead of SMBus Quick for the 0x50-0x5F address range.
Thus I would really appreciate if this code would not be duplicated.

Thanks,
-- 
Jean Delvare




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