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Date: Tue, 28 Dec 2021 18:51:40 +0200
From: Cosmin Tanislav <demonsingur@...il.com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: cosmin.tanislav@...log.com, Jean Delvare <jdelvare@...e.com>,
Jonathan Corbet <corbet@....net>, linux-hwmon@...r.kernel.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] hwmon: Add debugfs register access
On 12/28/21 18:13, Guenter Roeck wrote:
> On 12/27/21 2:42 PM, Cosmin Tanislav wrote:
>> From: Cosmin Tanislav <cosmin.tanislav@...log.com>
>>
>> Similar to IIO, create a device directory inside debugfs
>> mount point, and create a direct_reg_access file inside
>> that directory, if debugfs_reg_access callback is defined
>> inside hwmon_ops.
>>
>
> Patch looks good afaics. I don't want to apply it now (ie for 5.17),
> though, because it is getting close and we don't have a use case.
> If you have one in mind, I'd suggest to submit it together with
> this patch, or we'll have to wait until there is a user.
>
> Guenter
As I mentioned previously I have a local patch on top of the ADT7X10
refactor that uses this. I tested your modifications to my patchset on
the ADT7420 part and it seems to work just fine. I can push it on top of
either this patch or that patchset, your choice.
>
>> Signed-off-by: Cosmin Tanislav <cosmin.tanislav@...log.com>
>> ---
>> Documentation/hwmon/hwmon-kernel-api.rst | 9 +++
>> drivers/hwmon/hwmon.c | 97 ++++++++++++++++++++++++
>> include/linux/hwmon.h | 12 +++
>> 3 files changed, 118 insertions(+)
>>
>> diff --git a/Documentation/hwmon/hwmon-kernel-api.rst
>> b/Documentation/hwmon/hwmon-kernel-api.rst
>> index c41eb6108103..d568a0bfa5fb 100644
>> --- a/Documentation/hwmon/hwmon-kernel-api.rst
>> +++ b/Documentation/hwmon/hwmon-kernel-api.rst
>> @@ -136,6 +136,8 @@ The list of hwmon operations is defined as::
>> u32 attr, int, long *);
>> int (*write)(struct device *, enum hwmon_sensor_types type,
>> u32 attr, int, long);
>> + int (*reg_access)(struct device *dev, unsigned int reg,
>> + unsigned int writeval, unsigned int *readval);
>> };
>> It defines the following operations.
>> @@ -152,6 +154,13 @@ It defines the following operations.
>> Pointer to a function for writing a value to the chip. This
>> function is
>> optional, but must be provided if any writeable attributes exist.
>> +* reg_access:
>> + Pointer to a function for writing or reading a register to the chip.
>> + This function is optional.
>> + WARNING: Drivers implementing this function must block any access
>> that
>> + may cause issues such as power loss, board resets, flash
>> corruption or
>> + bricking.
>> +
>> Each sensor channel is described with struct hwmon_channel_info,
>> which is
>> defined as follows::
>> diff --git a/drivers/hwmon/hwmon.c b/drivers/hwmon/hwmon.c
>> index 3501a3ead4ba..027e5fc33114 100644
>> --- a/drivers/hwmon/hwmon.c
>> +++ b/drivers/hwmon/hwmon.c
>> @@ -10,6 +10,7 @@
>> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>> #include <linux/bitops.h>
>> +#include <linux/debugfs.h>
>> #include <linux/device.h>
>> #include <linux/err.h>
>> #include <linux/gfp.h>
>> @@ -35,6 +36,9 @@ struct hwmon_device {
>> struct list_head tzdata;
>> struct attribute_group group;
>> const struct attribute_group **groups;
>> + unsigned int cached_reg_addr;
>> + char read_buf[20];
>> + unsigned int read_buf_len;
>> };
>> #define to_hwmon_device(d) container_of(d, struct hwmon_device, dev)
>> @@ -64,6 +68,90 @@ struct hwmon_thermal_data {
>> struct thermal_zone_device *tzd;/* thermal zone device */
>> };
>> +static struct dentry *hwmon_debugfs_dentry;
>> +
>> +static ssize_t hwmon_debugfs_read_reg(struct file *file,
>> + char __user *userbuf,
>> + size_t count, loff_t *ppos)
>> +{
>> + struct hwmon_device *hwdev = file->private_data;
>> + unsigned int val;
>> + int ret;
>> +
>> + if (*ppos > 0)
>> + return simple_read_from_buffer(userbuf, count, ppos,
>> + hwdev->read_buf,
>> + hwdev->read_buf_len);
>> +
>> + ret = hwdev->chip->ops->reg_access(&hwdev->dev,
>> hwdev->cached_reg_addr,
>> + 0, &val);
>> + if (ret)
>> + return ret;
>> +
>> + hwdev->read_buf_len = snprintf(hwdev->read_buf,
>> sizeof(hwdev->read_buf),
>> + "0x%X\n", val);
>> +
>> + return simple_read_from_buffer(userbuf, count, ppos,
>> hwdev->read_buf,
>> + hwdev->read_buf_len);
>> +}
>> +
>> +static ssize_t hwmon_debugfs_write_reg(struct file *file,
>> + const char __user *userbuf,
>> + size_t count, loff_t *ppos)
>> +{
>> + struct hwmon_device *hwdev = file->private_data;
>> + unsigned int reg, val;
>> + char buf[80];
>> + int ret;
>> +
>> + count = min_t(size_t, count, sizeof(buf) - 1);
>> + if (copy_from_user(buf, userbuf, count))
>> + return -EFAULT;
>> +
>> + buf[count] = 0;
>> +
>> + ret = sscanf(buf, "%i %i", ®, &val);
>> +
>> + switch (ret) {
>> + case 1:
>> + hwdev->cached_reg_addr = reg;
>> + break;
>> + case 2:
>> + hwdev->cached_reg_addr = reg;
>> + ret = hwdev->chip->ops->reg_access(&hwdev->dev, reg, val, NULL);
>> + if (ret)
>> + return ret;
>> + break;
>> + default:
>> + return -EINVAL;
>> + }
>> +
>> + return count;
>> +}
>> +
>> +static const struct file_operations hwmon_debugfs_reg_fops = {
>> + .open = simple_open,
>> + .read = hwmon_debugfs_read_reg,
>> + .write = hwmon_debugfs_write_reg,
>> +};
>> +
>> +static void hwmon_device_register_debugfs(struct hwmon_device *hwdev)
>> +{
>> + struct dentry *dir = debugfs_create_dir(dev_name(&hwdev->dev),
>> + hwmon_debugfs_dentry);
>> +
>> + debugfs_create_file("direct_reg_access", 0644, dir, hwdev,
>> + &hwmon_debugfs_reg_fops);
>> +}
>> +
>> +static void hwmon_device_unregister_debugfs(struct hwmon_device *hwdev)
>> +{
>> + struct dentry *dir = debugfs_lookup(dev_name(&hwdev->dev),
>> + hwmon_debugfs_dentry);
>> +
>> + debugfs_remove_recursive(dir);
>> +}
>> +
>> static ssize_t
>> name_show(struct device *dev, struct device_attribute *attr, char *buf)
>> {
>> @@ -114,6 +202,8 @@ static void hwmon_dev_release(struct device *dev)
>> {
>> struct hwmon_device *hwdev = to_hwmon_device(dev);
>> + hwmon_device_unregister_debugfs(hwdev);
>> +
>> if (hwdev->group.attrs)
>> hwmon_free_attrs(hwdev->group.attrs);
>> kfree(hwdev->groups);
>> @@ -817,6 +907,9 @@ __hwmon_device_register(struct device *dev, const
>> char *name, void *drvdata,
>> }
>> }
>> + if (chip && chip->ops->reg_access)
>> + hwmon_device_register_debugfs(hwdev);
>> +
>> return hdev;
>> free_hwmon:
>> @@ -1062,12 +1155,16 @@ static int __init hwmon_init(void)
>> pr_err("couldn't register hwmon sysfs class\n");
>> return err;
>> }
>> +
>> + hwmon_debugfs_dentry = debugfs_create_dir("hwmon", NULL);
>> +
>> return 0;
>> }
>> static void __exit hwmon_exit(void)
>> {
>> class_unregister(&hwmon_class);
>> + debugfs_remove(hwmon_debugfs_dentry);
>> }
>> subsys_initcall(hwmon_init);
>> diff --git a/include/linux/hwmon.h b/include/linux/hwmon.h
>> index fad1f1df26df..587fb2931ac1 100644
>> --- a/include/linux/hwmon.h
>> +++ b/include/linux/hwmon.h
>> @@ -390,6 +390,16 @@ enum hwmon_intrusion_attributes {
>> * Channel number
>> * @val: Value to write
>> * The function returns 0 on success or a negative error number.
>> + * @reg_access:
>> + * Callback to read or write register values.
>> + * Parameters are:
>> + * @dev: Pointer to hardware monitoring device
>> + * @reg: Register address to read or write
>> + * @writeval:
>> + * Value to write to register. 0 when reading.
>> + * @readval:
>> + * Pointer to value read from register. NULL when writing.
>> + * The function returns 0 on success or a negative error number.
>> */
>> struct hwmon_ops {
>> umode_t (*is_visible)(const void *drvdata, enum
>> hwmon_sensor_types type,
>> @@ -400,6 +410,8 @@ struct hwmon_ops {
>> u32 attr, int channel, const char **str);
>> int (*write)(struct device *dev, enum hwmon_sensor_types type,
>> u32 attr, int channel, long val);
>> + int (*reg_access)(struct device *dev, unsigned int reg,
>> + unsigned int writeval, unsigned int *readval);
>> };
>> /**
>>
>
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