[PATCH v2] hwmon: (pmbus/core) Add a vout_command debugfs entry

[PATCH v2] hwmon: (pmbus/core) Add a vout_command debugfs entry

[Vincent Jardin via B4 Relay]

From: Vincent Jardin <vjardin@free.fr>

The vout hwmon attributes and the regulator get_voltage() callback
both report READ_VOUT.

On a regulator whose configuration applies a load line (droop),
READ_VOUT sits below the setpoint under load by design, so user space
cannot see what the regulator was actually set to.

max20730 already exposes a driver-specific vout_command entry. Add
vout<page>_command to the PMBus core debugfs, for every page with VOUT
and a readable VOUT_COMMAND, in millivolts like the in*_input attributes.

Signed-off-by: Vincent Jardin <vjardin@free.fr>
---
Changes in v2:
- Use pmbus_vout_command_mv(), simpler (Guenter Roeck).
- Link to v1: https://lore.kernel.org/r/20261108-for-upstream-pmbus-vout-command-debugfs-v1-v1-1-c7a063efb91c@free.fr
---
 drivers/hwmon/pmbus/pmbus_core.c | 39 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)

diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index 37b650b85d1c..6fb91dc1c627 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -3833,6 +3833,30 @@ static int pmbus_debugfs_get_status(void *data, u64 *val)
 DEFINE_DEBUGFS_ATTRIBUTE(pmbus_debugfs_ops_status, pmbus_debugfs_get_status,
 			 NULL, "0x%04llx\n");
 
+static int pmbus_debugfs_get_vout_command(void *data, u64 *val)
+{
+	struct pmbus_debugfs_entry *entry = data;
+	struct i2c_client *client = entry->client;
+	struct pmbus_data *pdata = i2c_get_clientdata(client);
+	int rc;
+
+	guard(pmbus_lock)(client);
+
+	rc = _pmbus_read_word_data(client, entry->page, 0xff, entry->reg);
+	if (rc < 0)
+		return rc;
+
+	rc = pmbus_vout_command_mv(pdata, entry->page, rc);
+	if (rc < 0)
+		return rc;
+
+	*val = rc;
+
+	return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(pmbus_debugfs_ops_vout_command,
+			 pmbus_debugfs_get_vout_command, NULL, "%llu\n");
+
 static ssize_t pmbus_debugfs_block_read(struct file *file, char __user *buf,
 					size_t count, loff_t *ppos)
 {
@@ -3940,11 +3964,11 @@ static void pmbus_init_debugfs(struct i2c_client *client,
 	 * device specific:
 	 *	ARRAY_SIZE(pmbus_debugfs_block_data) + 2
 	 * page specific:
-	 *	ARRAY_SIZE(pmbus_debugfs_status_data) + 1
+	 *	ARRAY_SIZE(pmbus_debugfs_status_data) + 2
 	 */
 	entries = devm_kcalloc(data->dev,
 			       ARRAY_SIZE(pmbus_debugfs_block_data) + 2 +
-			       data->info->pages * (ARRAY_SIZE(pmbus_debugfs_status_data) + 1),
+			       data->info->pages * (ARRAY_SIZE(pmbus_debugfs_status_data) + 2),
 			       sizeof(*entries), GFP_KERNEL);
 	if (!entries)
 		return;
@@ -4013,6 +4037,17 @@ static void pmbus_init_debugfs(struct i2c_client *client,
 						    &pmbus_debugfs_ops);
 			}
 		}
+
+		if ((data->info->func[page] & PMBUS_HAVE_VOUT) &&
+		    pmbus_check_word_register(client, page, PMBUS_VOUT_COMMAND)) {
+			entries[idx].client = client;
+			entries[idx].page = page;
+			entries[idx].reg = PMBUS_VOUT_COMMAND;
+			scnprintf(name, PMBUS_NAME_SIZE, "vout%d_command", page);
+			debugfs_create_file(name, 0444, debugfs,
+					    &entries[idx++],
+					    &pmbus_debugfs_ops_vout_command);
+		}
 	}
 }
 

---
base-commit: d4193d2a0ffa407478bce4a094e1ae085ceb38ec
change-id: 20261108-for-upstream-pmbus-vout-command-debugfs-v1-6fe3ec237b1a

Best regards,
-- 
Vincent Jardin <vjardin@free.fr>

Re: [PATCH v2] hwmon: (pmbus/core) Add a vout_command debugfs entry

[sashiko-bot]

> From: Vincent Jardin <vjardin@free.fr>
> 
> The vout hwmon attributes and the regulator get_voltage() callback
> both report READ_VOUT.
> 
> On a regulator whose configuration applies a load line (droop),
> READ_VOUT sits below the setpoint under load by design, so user space
> cannot see what the regulator was actually set to.
> 
> max20730 already exposes a driver-specific vout_command entry. Add
> vout<page>_command to the PMBus core debugfs, for every page with VOUT
> and a readable VOUT_COMMAND, in millivolts like the in*_input attributes.
> 
> Signed-off-by: Vincent Jardin <vjardin@free.fr>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261108-for-upstream-pmbus-vout-command-debugfs-v1-v2-1-b19d6cd18aae@free.fr?part=1

Re: [PATCH v2] hwmon: (pmbus/core) Add a vout_command debugfs entry

[Guenter Roeck]

Hi,

On Sun, Nov 08, 2026 at 08:56:36PM +0100, Vincent Jardin wrote:
> From: Vincent Jardin <vjardin@free.fr>
> 
> The vout hwmon attributes and the regulator get_voltage() callback
> both report READ_VOUT.
> 
> On a regulator whose configuration applies a load line (droop),
> READ_VOUT sits below the setpoint under load by design, so user space
> cannot see what the regulator was actually set to.
> 
> max20730 already exposes a driver-specific vout_command entry. Add
> vout<page>_command to the PMBus core debugfs, for every page with VOUT
> and a readable VOUT_COMMAND, in millivolts like the in*_input attributes.
> 
> Signed-off-by: Vincent Jardin <vjardin@free.fr>

This patch no longer applies to the upstream kernel due to commit 4dd10fbbeb9c
("treewide: Convert devm_kmalloc() family to the devm_kmalloc_obj() family").
Please rebase and resubmit.

Thanks,
Guenter