Re: [PATCH v2 16/16] hwmon: (mr75203) add debugfs to read and write temperature coefficients

[Guenter Roeck <linux@roeck-us.net>]

On Wed, Aug 17, 2022 at 05:43:21AM +0000, Eliav Farber wrote:
> This change adds debugfs to read and write TS coefficients - g, h, j and
> cal5.
> 
> The coefficients can vary between product and product, so to calibrate
> them it can be very useful to to be able to modify them on the fly.
> 
> e.g.
> 
> cat /sys/kernel/debug/940f23d0000.pvt/ts_coeff_cal5
> 4096
> 
> echo 83000 > sys/kernel/debug/940f23d0000.pvt/ts_coeff_g
> 

What happens if you write 0 into all those attributes, or 0xffffffff ?

Guenter

> Signed-off-by: Eliav Farber <farbere@amazon.com>
> ---
>  drivers/hwmon/mr75203.c | 196 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 196 insertions(+)
> 
> diff --git a/drivers/hwmon/mr75203.c b/drivers/hwmon/mr75203.c
> index 2898565afaab..ce34a44237e8 100644
> --- a/drivers/hwmon/mr75203.c
> +++ b/drivers/hwmon/mr75203.c
> @@ -9,6 +9,7 @@
>   */
>  #include <linux/bits.h>
>  #include <linux/clk.h>
> +#include <linux/debugfs.h>
>  #include <linux/hwmon.h>
>  #include <linux/module.h>
>  #include <linux/mod_devicetable.h>
> @@ -127,6 +128,7 @@ struct pvt_device {
>  	struct clk		*clk;
>  	struct reset_control	*rst;
>  	struct voltage_device	*vd;
> +	struct dentry		*dbgfs_dir;
>  	u32			t_num;
>  	u32			p_num;
>  	u32			v_num;
> @@ -139,6 +141,198 @@ struct pvt_device {
>  	u8			vm_ch_total;
>  };
>  
> +static ssize_t pvt_ts_coeff_h_read(struct file *file,
> +				   char __user *user_buf,
> +				   size_t count, loff_t *ppos)
> +{
> +	struct pvt_device *pvt = file->private_data;
> +	char buf[16];
> +	unsigned int len;
> +
> +	len = sprintf(buf, "%u\n", pvt->ts_coeff_h);
> +
> +	return simple_read_from_buffer(user_buf, count, ppos, buf, len);
> +}
> +
> +static ssize_t pvt_ts_coeff_h_write(struct file *file,
> +				    const char __user *user_buf,
> +				    size_t count, loff_t *ppos)
> +{
> +	struct pvt_device *pvt = file->private_data;
> +	int ret;
> +	u32 coeff;
> +
> +	ret = kstrtou32_from_user(user_buf, count, 0, &coeff);
> +	if (ret)
> +		return ret;
> +
> +	pvt->ts_coeff_h = coeff;
> +
> +	return count;
> +}
> +
> +static const struct file_operations pvt_ts_coeff_h_fops = {
> +	.read = pvt_ts_coeff_h_read,
> +	.write = pvt_ts_coeff_h_write,
> +	.open = simple_open,
> +	.owner = THIS_MODULE,
> +	.llseek = default_llseek,
> +};
> +
> +static ssize_t pvt_ts_coeff_g_read(struct file *file,
> +				   char __user *user_buf,
> +				   size_t count, loff_t *ppos)
> +{
> +	struct pvt_device *pvt = file->private_data;
> +	char buf[16];
> +	unsigned int len;
> +
> +	len = sprintf(buf, "%u\n", pvt->ts_coeff_g);
> +
> +	return simple_read_from_buffer(user_buf, count, ppos, buf, len);
> +}
> +
> +static ssize_t pvt_ts_coeff_g_write(struct file *file,
> +				    const char __user *user_buf,
> +				    size_t count, loff_t *ppos)
> +{
> +	struct pvt_device *pvt = file->private_data;
> +	int ret;
> +	u32 coeff;
> +
> +	ret = kstrtou32_from_user(user_buf, count, 0, &coeff);
> +	if (ret)
> +		return ret;
> +
> +	pvt->ts_coeff_g = coeff;
> +
> +	return count;
> +}
> +
> +static const struct file_operations pvt_ts_coeff_g_fops = {
> +	.read = pvt_ts_coeff_g_read,
> +	.write = pvt_ts_coeff_g_write,
> +	.open = simple_open,
> +	.owner = THIS_MODULE,
> +	.llseek = default_llseek,
> +};
> +
> +static ssize_t pvt_ts_coeff_j_read(struct file *file,
> +				   char __user *user_buf,
> +				   size_t count, loff_t *ppos)
> +{
> +	struct pvt_device *pvt = file->private_data;
> +	char buf[16];
> +	unsigned int len;
> +
> +	len = sprintf(buf, "%d\n", pvt->ts_coeff_j);
> +
> +	return simple_read_from_buffer(user_buf, count, ppos, buf, len);
> +}
> +
> +static ssize_t pvt_ts_coeff_j_write(struct file *file,
> +				    const char __user *user_buf,
> +				    size_t count, loff_t *ppos)
> +{
> +	struct pvt_device *pvt = file->private_data;
> +	int ret;
> +	s32 coeff;
> +
> +	ret = kstrtos32_from_user(user_buf, count, 0, &coeff);
> +	if (ret)
> +		return ret;
> +
> +	pvt->ts_coeff_j = coeff;
> +
> +	return count;
> +}
> +
> +static const struct file_operations pvt_ts_coeff_j_fops = {
> +	.read = pvt_ts_coeff_j_read,
> +	.write = pvt_ts_coeff_j_write,
> +	.open = simple_open,
> +	.owner = THIS_MODULE,
> +	.llseek = default_llseek,
> +};
> +
> +static ssize_t pvt_ts_coeff_cal5_read(struct file *file,
> +				      char __user *user_buf,
> +				      size_t count, loff_t *ppos)
> +{
> +	struct pvt_device *pvt = file->private_data;
> +	char buf[16];
> +	unsigned int len;
> +
> +	len = sprintf(buf, "%u\n", pvt->ts_coeff_cal5);
> +
> +	return simple_read_from_buffer(user_buf, count, ppos, buf, len);
> +}
> +
> +static ssize_t pvt_ts_coeff_cal5_write(struct file *file,
> +				       const char __user *user_buf,
> +				       size_t count, loff_t *ppos)
> +{
> +	struct pvt_device *pvt = file->private_data;
> +	int ret;
> +	u32 coeff;
> +
> +	ret = kstrtou32_from_user(user_buf, count, 0, &coeff);
> +	if (ret)
> +		return ret;
> +
> +	if (coeff == 0)
> +		return -EINVAL;
> +
> +	pvt->ts_coeff_cal5 = coeff;
> +
> +	return count;
> +}
> +
> +static const struct file_operations pvt_ts_coeff_cal5_fops = {
> +	.read = pvt_ts_coeff_cal5_read,
> +	.write = pvt_ts_coeff_cal5_write,
> +	.open = simple_open,
> +	.owner = THIS_MODULE,
> +	.llseek = default_llseek,
> +};
> +
> +static void devm_pvt_ts_dbgfs_remove(void *data)
> +{
> +	struct pvt_device *pvt = (struct pvt_device *)data;
> +
> +	debugfs_remove_recursive(pvt->dbgfs_dir);
> +	pvt->dbgfs_dir = NULL;
> +}
> +
> +static int pvt_ts_dbgfs_create(struct pvt_device *pvt, struct device *dev)
> +{
> +	int ret;
> +
> +	pvt->dbgfs_dir = debugfs_create_dir(dev_name(dev), NULL);
> +	if (!pvt->dbgfs_dir) {
> +		dev_err(dev, "Failed to create dbgfs_dir\n");
> +		return -EINVAL;
> +	}
> +
> +	debugfs_create_file("ts_coeff_h", 0644, pvt->dbgfs_dir, pvt,
> +			    &pvt_ts_coeff_h_fops);
> +	debugfs_create_file("ts_coeff_g", 0644, pvt->dbgfs_dir, pvt,
> +			    &pvt_ts_coeff_g_fops);
> +	debugfs_create_file("ts_coeff_j", 0644, pvt->dbgfs_dir, pvt,
> +			    &pvt_ts_coeff_j_fops);
> +	debugfs_create_file("ts_coeff_cal5", 0644, pvt->dbgfs_dir,  pvt,
> +			    &pvt_ts_coeff_cal5_fops);
> +
> +	ret = devm_add_action_or_reset(dev, devm_pvt_ts_dbgfs_remove, pvt);
> +	if (ret) {
> +		dev_err(dev, "failed to add action to remove pvt dbgfs (%d)\n",
> +			ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
>  static umode_t pvt_is_visible(const void *data, enum hwmon_sensor_types type,
>  			      u32 attr, int channel)
>  {
> @@ -655,6 +849,8 @@ static int mr75203_probe(struct platform_device *pdev)
>  		dev_dbg(dev, "ts-coeff: h = %u, g = %u, j = %d, cal5 = %u\n",
>  			pvt->ts_coeff_h, pvt->ts_coeff_g, pvt->ts_coeff_j,
>  			pvt->ts_coeff_cal5);
> +
> +		pvt_ts_dbgfs_create(pvt, dev);
>  	}
>  
>  	if (pd_num) {