[v2,1/3] i2c: Add parameters to sysfs-added i2c devices

From: Corey Minyard <cminyard@mvista.com>

Some devices might need parameters to control their operation,
add the ability to pass these parameters to the client.

This also makes the parsing of sysfs-added I2C devices a little
more flexible, allowing tabs and arbitrary numbers of spaces.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
---
 drivers/i2c/i2c-core.c | 43 +++++++++++++++++++++++++++++++------------
 include/linux/i2c.h    |  3 +++
 2 files changed, 34 insertions(+), 12 deletions(-)

On 5/10/2016 10:11 AM, minyard@acm.org wrote:
> From: Corey Minyard <cminyard@mvista.com>
>
> Some devices might need parameters to control their operation,
> add the ability to pass these parameters to the client.
>
> This also makes the parsing of sysfs-added I2C devices a little
> more flexible, allowing tabs and arbitrary numbers of spaces.
>
> Signed-off-by: Corey Minyard <cminyard@mvista.com>
Tested on QDF2432 with I2C IPMI client to ensure no regressions are 
introduced.
Tested-by: Naveen Kaje <nkaje@codeaurora.org>

> ---
>   drivers/i2c/i2c-core.c | 43 +++++++++++++++++++++++++++++++------------
>   include/linux/i2c.h    |  3 +++
>   2 files changed, 34 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index e584d88..069c385 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -51,6 +51,7 @@
>   #include <linux/pm_domain.h>
>   #include <linux/pm_runtime.h>
>   #include <linux/pm_wakeirq.h>
> +#include <linux/ctype.h>
>   #include <linux/property.h>
>   #include <linux/rwsem.h>
>   #include <linux/slab.h>
> @@ -780,7 +781,10 @@ static void i2c_device_shutdown(struct device *dev)
>   
>   static void i2c_client_dev_release(struct device *dev)
>   {
> -	kfree(to_i2c_client(dev));
> +	struct i2c_client *client = to_i2c_client(dev);
> +
> +	kfree(client->parms);
> +	kfree(client);
>   }
>   
>   static ssize_t
> @@ -1047,6 +1051,13 @@ i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
>   	client->flags = info->flags;
>   	client->addr = info->addr;
>   	client->irq = info->irq;
> +	if (info->parms) {
> +		client->parms = kstrdup(info->parms, GFP_KERNEL);
> +		if (!client->parms) {
> +			dev_err(&adap->dev, "Out of memory allocating parms\n");
> +			goto out_err_silent;
> +		}
> +	}
>   
>   	strlcpy(client->name, info->type, sizeof(client->name));
>   
> @@ -1196,31 +1207,39 @@ i2c_sysfs_new_device(struct device *dev, struct device_attribute *attr,
>   	struct i2c_adapter *adap = to_i2c_adapter(dev);
>   	struct i2c_board_info info;
>   	struct i2c_client *client;
> -	char *blank, end;
> +	char *pos, end;
>   	int res;
>   
>   	memset(&info, 0, sizeof(struct i2c_board_info));
>   
> -	blank = strchr(buf, ' ');
> -	if (!blank) {
> +	pos = strpbrk(buf, " \t");
> +	if (!pos) {
>   		dev_err(dev, "%s: Missing parameters\n", "new_device");
>   		return -EINVAL;
>   	}
> -	if (blank - buf > I2C_NAME_SIZE - 1) {
> +	if (pos - buf > I2C_NAME_SIZE - 1) {
>   		dev_err(dev, "%s: Invalid device name\n", "new_device");
>   		return -EINVAL;
>   	}
> -	memcpy(info.type, buf, blank - buf);
> +	memcpy(info.type, buf, pos - buf);
>   
> -	/* Parse remaining parameters, reject extra parameters */
> -	res = sscanf(++blank, "%hi%c", &info.addr, &end);
> -	if (res < 1) {
> +	while (isspace(*pos))
> +		pos++;
> +
> +	/* Parse address, saving remaining parameters. */
> +	res = sscanf(pos, "%hi%c", &info.addr, &end);
> +	if (res < 1 || (res > 1 && !isspace(end))) {
>   		dev_err(dev, "%s: Can't parse I2C address\n", "new_device");
>   		return -EINVAL;
>   	}
> -	if (res > 1  && end != '\n') {
> -		dev_err(dev, "%s: Extra parameters\n", "new_device");
> -		return -EINVAL;
> +	if (res > 1) {
> +		/* Extra parms, skip the address and space. */
> +		while (!isspace(*pos))
> +			pos++;
> +		while (isspace(*pos))
> +			pos++;
> +		if (*pos)
> +			info.parms = pos;
>   	}
>   
>   	if ((info.addr & I2C_ADDR_OFFSET_TEN_BIT) == I2C_ADDR_OFFSET_TEN_BIT) {
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index 200cf13b..35db0dd 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -225,6 +225,7 @@ struct i2c_client {
>   	char name[I2C_NAME_SIZE];
>   	struct i2c_adapter *adapter;	/* the adapter we sit on	*/
>   	struct device dev;		/* the device structure		*/
> +	char *parms;			/* sysfs extra parms		*/
>   	int irq;			/* irq issued by device		*/
>   	struct list_head detected;
>   #if IS_ENABLED(CONFIG_I2C_SLAVE)
> @@ -282,6 +283,7 @@ static inline int i2c_slave_event(struct i2c_client *client,
>    * @archdata: copied into i2c_client.dev.archdata
>    * @of_node: pointer to OpenFirmware device node
>    * @fwnode: device node supplied by the platform firmware
> + * @parms: Parameters supplied on the sysfs command line
>    * @irq: stored in i2c_client.irq
>    *
>    * I2C doesn't actually support hardware probing, although controllers and
> @@ -303,6 +305,7 @@ struct i2c_board_info {
>   	struct dev_archdata	*archdata;
>   	struct device_node *of_node;
>   	struct fwnode_handle *fwnode;
> +	char            *parms;
>   	int		irq;
>   };
>   

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> From: Corey Minyard <cminyard@mvista.com>
> 
> Some devices might need parameters to control their operation,
> add the ability to pass these parameters to the client.

Cleaning up old patches from patchwork once in a while...

I don't think it is a good way to add parsers to each and every I2C
client driver which wants to read extra parameters. Maybe there is a
more generic way to configure at runtime these days. I never needed
something like this, so sadly I can't give a pointer.