[PATCH 1/3] usb: typec: altmodes/displayport: Add pin assignment helper

[Prashant Malani]

The code to extract a peripheral's currently supported Pin Assignments
is repeated in a couple of locations. Factor it out into a separate
function.

This will also make it easier to add fixes (we only need to update 1
location instead of 2).

Fixes: c1e5c2f0cb8a ("usb: typec: altmodes/displayport: correct pin assignment for UFP receptacles")
Cc: stable@xxxxxxxxxxxxxxx
Cc: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
Signed-off-by: Prashant Malani <pmalani@xxxxxxxxxxxx>
---

While this patch doesn't fix anything, it is required by the actual
fix (which is Patch 2/3 in this series). So, I've add the "Fixes" tag
and "Cc stable" tag to ensure that both patches are picked.

If this is the incorrect approach and there is a better way, my
apologies, and please let me know the appropriate process.

 drivers/usb/typec/altmodes/displayport.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
index 06fb4732f8cd..f9d4a7648bc9 100644
--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -420,6 +420,18 @@ static const char * const pin_assignments[] = {
 	[DP_PIN_ASSIGN_F] = "F",
 };
 
+/*
+ * Helper function to extract a peripheral's currently supported
+ * Pin Assignments from its DisplayPort alternate mode state.
+ */
+static u8 get_current_pin_assignments(struct dp_altmode *dp)
+{
+	if (DP_CONF_CURRENTLY(dp->data.conf) == DP_CONF_DFP_D)
+		return DP_CAP_UFP_D_PIN_ASSIGN(dp->alt->vdo);
+	else
+		return DP_CAP_DFP_D_PIN_ASSIGN(dp->alt->vdo);
+}
+
 static ssize_t
 pin_assignment_store(struct device *dev, struct device_attribute *attr,
 		     const char *buf, size_t size)
@@ -446,10 +458,7 @@ pin_assignment_store(struct device *dev, struct device_attribute *attr,
 		goto out_unlock;
 	}
 
-	if (DP_CONF_CURRENTLY(dp->data.conf) == DP_CONF_DFP_D)
-		assignments = DP_CAP_UFP_D_PIN_ASSIGN(dp->alt->vdo);
-	else
-		assignments = DP_CAP_DFP_D_PIN_ASSIGN(dp->alt->vdo);
+	assignments = get_current_pin_assignments(dp);
 
 	if (!(DP_CONF_GET_PIN_ASSIGN(conf) & assignments)) {
 		ret = -EINVAL;
@@ -486,10 +495,7 @@ static ssize_t pin_assignment_show(struct device *dev,
 
 	cur = get_count_order(DP_CONF_GET_PIN_ASSIGN(dp->data.conf));
 
-	if (DP_CONF_CURRENTLY(dp->data.conf) == DP_CONF_DFP_D)
-		assignments = DP_CAP_UFP_D_PIN_ASSIGN(dp->alt->vdo);
-	else
-		assignments = DP_CAP_DFP_D_PIN_ASSIGN(dp->alt->vdo);
+	assignments = get_current_pin_assignments(dp);
 
 	for (i = 0; assignments; assignments >>= 1, i++) {
 		if (assignments & 1) {
-- 
2.39.0.314.g84b9a713c41-goog