diff mbox series

[v3] usb: pd: Exposing the Peak Current value of Fixed Supplies to user space

Message ID 20231002142240.2641962-1-heikki.krogerus@linux.intel.com (mailing list archive)
State Accepted
Commit 568441b7d45fc7198a89b522d721428f2005c356
Headers show
Series [v3] usb: pd: Exposing the Peak Current value of Fixed Supplies to user space | expand

Commit Message

Heikki Krogerus Oct. 2, 2023, 2:22 p.m. UTC 
Exposing the value of the field as is.

The Peak Current value has to be interpreted as described
in Table 6-10 (Fixed Power Source Peak Current Capability)
of the USB Power Delivery Specification, but that
interpretation will be done in user space, not in kernel.

Suggested-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
---
v3: There was something wrong with my reStructuredText style table. While
    attempting to fix it, I realised that in the latest USB PD specification
    there are some small changes in the Table 6-10, so I'm skipping that table
    from the documentation, and just giving a general explanation for the sysfs
    file instead.

    I took the liberty of including Reviewed-by tag from Guenter in any case.
    The code has not changed.

---
 .../ABI/testing/sysfs-class-usb_power_delivery         |  7 +++++++
 drivers/usb/typec/pd.c                                 | 10 ++++------
 include/linux/usb/pd.h                                 |  1 +
 3 files changed, 12 insertions(+), 6 deletions(-)
diff mbox series

Patch

diff --git a/Documentation/ABI/testing/sysfs-class-usb_power_delivery b/Documentation/ABI/testing/sysfs-class-usb_power_delivery
index 1bf9d1d7902c..61d233c320ea 100644
--- a/Documentation/ABI/testing/sysfs-class-usb_power_delivery
+++ b/Documentation/ABI/testing/sysfs-class-usb_power_delivery
@@ -124,6 +124,13 @@  Contact:	Heikki Krogerus <heikki.krogerus@linux.intel.com>
 Description:
 		The voltage the supply supports in millivolts.
 
+What:		/sys/class/usb_power_delivery/.../source-capabilities/<position>:fixed_supply/peak_current
+Date:		October 2023
+Contact:	Heikki Krogerus <heikki.krogerus@linux.intel.com>
+Description:
+		This file shows the value of the Fixed Power Source Peak Current
+		Capability field.
+
 What:		/sys/class/usb_power_delivery/.../source-capabilities/<position>:fixed_supply/maximum_current
 Date:		May 2022
 Contact:	Heikki Krogerus <heikki.krogerus@linux.intel.com>
diff --git a/drivers/usb/typec/pd.c b/drivers/usb/typec/pd.c
index 8cc66e4467c4..85d015cdbe1f 100644
--- a/drivers/usb/typec/pd.c
+++ b/drivers/usb/typec/pd.c
@@ -83,14 +83,12 @@  unchunked_extended_messages_supported_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(unchunked_extended_messages_supported);
 
-/*
- * REVISIT: Peak Current requires access also to the RDO.
 static ssize_t
 peak_current_show(struct device *dev, struct device_attribute *attr, char *buf)
 {
-	...
+	return sysfs_emit(buf, "%u\n", (to_pdo(dev)->pdo >> PDO_FIXED_PEAK_CURR_SHIFT) & 3);
 }
-*/
+static DEVICE_ATTR_RO(peak_current);
 
 static ssize_t
 fast_role_swap_current_show(struct device *dev, struct device_attribute *attr, char *buf)
@@ -135,7 +133,7 @@  static struct attribute *source_fixed_supply_attrs[] = {
 	&dev_attr_usb_communication_capable.attr,
 	&dev_attr_dual_role_data.attr,
 	&dev_attr_unchunked_extended_messages_supported.attr,
-	/*&dev_attr_peak_current.attr,*/
+	&dev_attr_peak_current.attr,
 	&dev_attr_voltage.attr,
 	&maximum_current_attr.attr,
 	NULL
@@ -144,7 +142,7 @@  static struct attribute *source_fixed_supply_attrs[] = {
 static umode_t fixed_attr_is_visible(struct kobject *kobj, struct attribute *attr, int n)
 {
 	if (to_pdo(kobj_to_dev(kobj))->object_position &&
-	    /*attr != &dev_attr_peak_current.attr &&*/
+	    attr != &dev_attr_peak_current.attr &&
 	    attr != &dev_attr_voltage.attr &&
 	    attr != &maximum_current_attr.attr &&
 	    attr != &operational_current_attr.attr)
diff --git a/include/linux/usb/pd.h b/include/linux/usb/pd.h
index c59fb79a42e8..eb626af0e4e7 100644
--- a/include/linux/usb/pd.h
+++ b/include/linux/usb/pd.h
@@ -228,6 +228,7 @@  enum pd_pdo_type {
 #define PDO_FIXED_UNCHUNK_EXT		BIT(24) /* Unchunked Extended Message supported (Source) */
 #define PDO_FIXED_FRS_CURR_MASK		(BIT(24) | BIT(23)) /* FR_Swap Current (Sink) */
 #define PDO_FIXED_FRS_CURR_SHIFT	23
+#define PDO_FIXED_PEAK_CURR_SHIFT	20
 #define PDO_FIXED_VOLT_SHIFT		10	/* 50mV units */
 #define PDO_FIXED_CURR_SHIFT		0	/* 10mA units */