Re: [PATCH v6 2/2] hwmon: (ucd9000) Add debugfs attributes to provide mfr_status

[Guenter Roeck]

On Fri, Mar 16, 2018 at 03:04:47PM -0500, Eddie James wrote:
> 
> 
> On 03/16/2018 02:59 PM, Guenter Roeck wrote:
> >On Fri, Mar 16, 2018 at 02:25:59PM -0500, Eddie James wrote:
> >>From: Christopher Bostic <cbostic@xxxxxxxxxxxxxxxxxx>
> >>
> >>Expose the gpiN_fault fields of mfr_status as individual debugfs
> >>attributes. This provides a way for users to be easily notified of gpi
> >>faults. Also provide the whole mfr_status register in debugfs.
> >>
> >>Signed-off-by: Christopher Bostic <cbostic@xxxxxxxxxxxxxxxxxx>
> >>Signed-off-by: Andrew Jeffery <andrew@xxxxxxxx>
> >>Signed-off-by: Eddie James <eajames@xxxxxxxxxxxxxxxxxx>
> >>---
> >>  drivers/hwmon/pmbus/ucd9000.c | 138 +++++++++++++++++++++++++++++++++++++++++-
> >>  1 file changed, 137 insertions(+), 1 deletion(-)
> >>
> >>diff --git a/drivers/hwmon/pmbus/ucd9000.c b/drivers/hwmon/pmbus/ucd9000.c
> >>index ef2c5bf..88c98fb 100644
> >>--- a/drivers/hwmon/pmbus/ucd9000.c
> >>+++ b/drivers/hwmon/pmbus/ucd9000.c
> >>@@ -19,6 +19,7 @@
> >>   * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
> >>   */
> >>+#include <linux/debugfs.h>
> >>  #include <linux/kernel.h>
> >>  #include <linux/module.h>
> >>  #include <linux/of_device.h>
> >>@@ -37,6 +38,7 @@
> >>  #define UCD9000_NUM_PAGES		0xd6
> >>  #define UCD9000_FAN_CONFIG_INDEX	0xe7
> >>  #define UCD9000_FAN_CONFIG		0xe8
> >>+#define UCD9000_MFR_STATUS		0xf3
> >>  #define UCD9000_GPIO_SELECT		0xfa
> >>  #define UCD9000_GPIO_CONFIG		0xfb
> >>  #define UCD9000_DEVICE_ID		0xfd
> >>@@ -64,15 +66,24 @@
> >>  #define UCD901XX_NUM_GPIOS	26
> >>  #define UCD90910_NUM_GPIOS	26
> >>+#define UCD9000_DEBUGFS_NAME_LEN	24
> >>+#define UCD9000_GPI_COUNT		8
> >>+
> >>  struct ucd9000_data {
> >>  	u8 fan_data[UCD9000_NUM_FAN][I2C_SMBUS_BLOCK_MAX];
> >>  	struct pmbus_driver_info info;
> >>  #ifdef CONFIG_GPIOLIB
> >>  	struct gpio_chip gpio;
> >>  #endif
> >>+	struct dentry *debugfs;
> >>  };
> >>  #define to_ucd9000_data(_info) container_of(_info, struct ucd9000_data, info)
> >>+struct ucd9000_debugfs_entry {
> >>+	struct i2c_client *client;
> >>+	u8 index;
> >>+};
> >>+
> >>  static int ucd9000_get_fan_config(struct i2c_client *client, int fan)
> >>  {
> >>  	int fan_config = 0;
> >>@@ -359,6 +370,122 @@ static void ucd9000_probe_gpio(struct i2c_client *client,
> >>  }
> >>  #endif /* CONFIG_GPIOLIB */
> >>+#ifdef CONFIG_DEBUG_FS
> >>+static int ucd9000_get_mfr_status(struct i2c_client *client, u8 *buffer)
> >>+{
> >>+	int ret = pmbus_set_page(client, 0);
> >>+
> >>+	if (ret < 0)
> >>+		return ret;
> >>+
> >>+	return i2c_smbus_read_block_data(client, UCD9000_MFR_STATUS, buffer);
> >>+}
> >>+
> >>+static int ucd9000_debugfs_show_mfr_status_bit(void *data, u64 *val)
> >>+{
> >>+	struct ucd9000_debugfs_entry *entry = data;
> >>+	struct i2c_client *client = entry->client;
> >>+	u8 buffer[I2C_SMBUS_BLOCK_MAX];
> >>+	int ret;
> >>+
> >>+	ret = ucd9000_get_mfr_status(client, buffer);
> >>+	if (ret < 0)
> >>+		return ret;
> >>+
> >>+	/*
> >>+	 * Attribute only created for devices with gpi fault bits at bits
> >>+	 * 16-23, which is the second byte of the response.
> >>+	 */
> >>+	*val = !!(buffer[1] & BIT(entry->index));
> >>+
> >>+	return 0;
> >>+}
> >>+DEFINE_DEBUGFS_ATTRIBUTE(ucd9000_debugfs_mfr_status_bit,
> >>+			 ucd9000_debugfs_show_mfr_status_bit, NULL, "%1lld\n");
> >>+
> >>+static ssize_t ucd9000_debugfs_read_mfr_status(struct file *file,
> >>+					       char __user *buf, size_t count,
> >>+					       loff_t *ppos)
> >>+{
> >>+	struct i2c_client *client = file->private_data;
> >>+	u8 buffer[I2C_SMBUS_BLOCK_MAX];
> >>+	char str[(I2C_SMBUS_BLOCK_MAX * 2) + 2];
> >>+	char *res;
> >>+	int rc;
> >>+
> >>+	rc = ucd9000_get_mfr_status(client, buffer);
> >>+	if (rc < 0)
> >>+		return rc;
> >>+
> >>+	res = bin2hex(str, buffer, min(rc, I2C_SMBUS_BLOCK_MAX));
> >>+	*res++ = '\n';
> >>+	*res++ = 0;
> >>+
> >Unless I am missing something, this now returns the terminating '\0'
> >to the user. Is this really what you want ?
> 
> Yes, that was my intention. I thought that was normal. It worked fine when I
> cat'ed the file. Up to you, I can change it if you like.
> 
Please do. I suspect that you'll see the '\0' if you send the output to od.
That is unexpected. I browsed through the kernel and was unable to find
any other code doing the same, so we should not be the ones starting it.

Example is DEFINE_DEBUGFS_ATTRIBUTE, which ends up calling simple_attr_read().
This in turn passes the result of scnprintf() or strlen() to
simple_read_from_buffer(). Both not include the terminating '\0'.

Thanks,
Guenter

> Thanks,
> Eddie
> 
> >
> >I see other code adding the terminator, but it doesn't usually return it
> >to the user.
> >
> >Guenter
> >
> >>+	return simple_read_from_buffer(buf, count, ppos, str, res - str);
> >>+}
> >>+
> >>+static const struct file_operations ucd9000_debugfs_show_mfr_status_fops = {
> >>+	.llseek = noop_llseek,
> >>+	.read = ucd9000_debugfs_read_mfr_status,
> >>+	.open = simple_open,
> >>+};
> >>+
> >>+static int ucd9000_init_debugfs(struct i2c_client *client,
> >>+				const struct i2c_device_id *mid,
> >>+				struct ucd9000_data *data)
> >>+{
> >>+	struct dentry *debugfs;
> >>+	struct ucd9000_debugfs_entry *entries;
> >>+	int i;
> >>+	char name[UCD9000_DEBUGFS_NAME_LEN];
> >>+
> >>+	debugfs = pmbus_get_debugfs_dir(client);
> >>+	if (!debugfs)
> >>+		return -ENOENT;
> >>+
> >>+	data->debugfs = debugfs_create_dir(client->name, debugfs);
> >>+	if (!data->debugfs)
> >>+		return -ENOENT;
> >>+
> >>+	/*
> >>+	 * Of the chips this driver supports, only the UCD9090, UCD90160,
> >>+	 * and UCD90910 report GPI faults in their MFR_STATUS register, so only
> >>+	 * create the GPI fault debugfs attributes for those chips.
> >>+	 */
> >>+	if (mid->driver_data == ucd9090 || mid->driver_data == ucd90160 ||
> >>+	    mid->driver_data == ucd90910) {
> >>+		entries = devm_kzalloc(&client->dev,
> >>+				       sizeof(*entries) * UCD9000_GPI_COUNT,
> >>+				       GFP_KERNEL);
> >>+		if (!entries)
> >>+			return -ENOMEM;
> >>+
> >>+		for (i = 0; i < UCD9000_GPI_COUNT; i++) {
> >>+			entries[i].client = client;
> >>+			entries[i].index = i;
> >>+			scnprintf(name, UCD9000_DEBUGFS_NAME_LEN,
> >>+				  "gpi%d_alarm", i + 1);
> >>+			debugfs_create_file(name, 0444, data->debugfs,
> >>+					    &entries[i],
> >>+					    &ucd9000_debugfs_mfr_status_bit);
> >>+		}
> >>+	}
> >>+
> >>+	scnprintf(name, UCD9000_DEBUGFS_NAME_LEN, "mfr_status");
> >>+	debugfs_create_file(name, 0444, data->debugfs, client,
> >>+			    &ucd9000_debugfs_show_mfr_status_fops);
> >>+
> >>+	return 0;
> >>+}
> >>+#else
> >>+static int ucd9000_init_debugfs(struct i2c_client *client,
> >>+				const struct i2c_device_id *mid,
> >>+				struct ucd9000_data *data)
> >>+{
> >>+	return 0;
> >>+}
> >>+#endif /* CONFIG_DEBUG_FS */
> >>+
> >>  static int ucd9000_probe(struct i2c_client *client,
> >>  			 const struct i2c_device_id *id)
> >>  {
> >>@@ -475,7 +602,16 @@ static int ucd9000_probe(struct i2c_client *client,
> >>  	ucd9000_probe_gpio(client, mid, data);
> >>-	return pmbus_do_probe(client, mid, info);
> >>+	ret = pmbus_do_probe(client, mid, info);
> >>+	if (ret)
> >>+		return ret;
> >>+
> >>+	ret = ucd9000_init_debugfs(client, mid, data);
> >>+	if (ret)
> >>+		dev_warn(&client->dev, "Failed to register debugfs: %d\n",
> >>+			 ret);
> >>+
> >>+	return 0;
> >>  }
> >>  /* This is the driver that will be inserted */
> >>-- 
> >>1.8.3.1
> >>
> >>--
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