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[PATCH v2 4/5] usb: typec: Implement alternate mode priority handling

Andrei Kuchynski posted 5 patches 5 months, 2 weeks ago
There is a newer version of this series
[PATCH v2 4/5] usb: typec: Implement alternate mode priority handling
Posted by Andrei Kuchynski 5 months, 2 weeks ago 
This patch introduces APIs to manage the priority of USB Type-C alternate
modes. These APIs allow for setting and retrieving a priority number for
each mode. If a new priority value conflicts with an existing mode's
priority, the priorities of the conflicting mode and all subsequent modes
are automatically incremented to ensure uniqueness.

Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
---
 drivers/usb/typec/Makefile         |  2 +-
 drivers/usb/typec/mode_selection.c | 38 ++++++++++++++++++++++++++++++
 drivers/usb/typec/mode_selection.h |  6 +++++
 include/linux/usb/typec_altmode.h  |  1 +
 4 files changed, 46 insertions(+), 1 deletion(-)
 create mode 100644 drivers/usb/typec/mode_selection.c
 create mode 100644 drivers/usb/typec/mode_selection.h

diff --git a/drivers/usb/typec/Makefile b/drivers/usb/typec/Makefile
index 7a368fea61bc..8a6a1c663eb6 100644
--- a/drivers/usb/typec/Makefile
+++ b/drivers/usb/typec/Makefile
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_TYPEC)		+= typec.o
-typec-y				:= class.o mux.o bus.o pd.o retimer.o
+typec-y				:= class.o mux.o bus.o pd.o retimer.o mode_selection.o
 typec-$(CONFIG_ACPI)		+= port-mapper.o
 obj-$(CONFIG_TYPEC)		+= altmodes/
 obj-$(CONFIG_TYPEC_TCPM)	+= tcpm/
diff --git a/drivers/usb/typec/mode_selection.c b/drivers/usb/typec/mode_selection.c
new file mode 100644
index 000000000000..2179bf25f5d4
--- /dev/null
+++ b/drivers/usb/typec/mode_selection.c
@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2025 Google LLC.
+ */
+
+#include "mode_selection.h"
+#include "class.h"
+#include "bus.h"
+
+static int increment_duplicated_priority(struct device *dev, void *data)
+{
+	struct typec_altmode **alt_target = (struct typec_altmode **)data;
+
+	if (is_typec_altmode(dev)) {
+		struct typec_altmode *alt = to_typec_altmode(dev);
+
+		if (alt != *alt_target && alt->priority == (*alt_target)->priority) {
+			alt->priority++;
+			*alt_target = alt;
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
+void typec_mode_set_priority(struct typec_altmode *alt,
+		const unsigned int priority)
+{
+	struct typec_port *port = to_typec_port(alt->dev.parent);
+	int res = 1;
+
+	alt->priority = priority;
+
+	while (res)
+		res = device_for_each_child(&port->dev, &alt,
+				increment_duplicated_priority);
+}
diff --git a/drivers/usb/typec/mode_selection.h b/drivers/usb/typec/mode_selection.h
new file mode 100644
index 000000000000..cbf5a37e6404
--- /dev/null
+++ b/drivers/usb/typec/mode_selection.h
@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/usb/typec_altmode.h>
+
+void typec_mode_set_priority(struct typec_altmode *alt,
+		const unsigned int priority);
diff --git a/include/linux/usb/typec_altmode.h b/include/linux/usb/typec_altmode.h
index b3c0866ea70f..571c6e00b54f 100644
--- a/include/linux/usb/typec_altmode.h
+++ b/include/linux/usb/typec_altmode.h
@@ -28,6 +28,7 @@ struct typec_altmode {
 	int				mode;
 	u32				vdo;
 	unsigned int			active:1;
+	unsigned int			priority;
 
 	char				*desc;
 	const struct typec_altmode_ops	*ops;
-- 
2.51.0.rc2.233.g662b1ed5c5-goog
Re: [PATCH v2 4/5] usb: typec: Implement alternate mode priority handling
Posted by Heikki Krogerus 5 months, 1 week ago 
On Mon, Aug 25, 2025 at 02:57:49PM +0000, Andrei Kuchynski wrote:
> This patch introduces APIs to manage the priority of USB Type-C alternate
> modes. These APIs allow for setting and retrieving a priority number for
> each mode. If a new priority value conflicts with an existing mode's
> priority, the priorities of the conflicting mode and all subsequent modes
> are automatically incremented to ensure uniqueness.
> 
> Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
> ---
>  drivers/usb/typec/Makefile         |  2 +-
>  drivers/usb/typec/mode_selection.c | 38 ++++++++++++++++++++++++++++++
>  drivers/usb/typec/mode_selection.h |  6 +++++
>  include/linux/usb/typec_altmode.h  |  1 +
>  4 files changed, 46 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/usb/typec/mode_selection.c
>  create mode 100644 drivers/usb/typec/mode_selection.h
> 
> diff --git a/drivers/usb/typec/Makefile b/drivers/usb/typec/Makefile
> index 7a368fea61bc..8a6a1c663eb6 100644
> --- a/drivers/usb/typec/Makefile
> +++ b/drivers/usb/typec/Makefile
> @@ -1,6 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0
>  obj-$(CONFIG_TYPEC)		+= typec.o
> -typec-y				:= class.o mux.o bus.o pd.o retimer.o
> +typec-y				:= class.o mux.o bus.o pd.o retimer.o mode_selection.o
>  typec-$(CONFIG_ACPI)		+= port-mapper.o
>  obj-$(CONFIG_TYPEC)		+= altmodes/
>  obj-$(CONFIG_TYPEC_TCPM)	+= tcpm/
> diff --git a/drivers/usb/typec/mode_selection.c b/drivers/usb/typec/mode_selection.c
> new file mode 100644
> index 000000000000..2179bf25f5d4
> --- /dev/null
> +++ b/drivers/usb/typec/mode_selection.c
> @@ -0,0 +1,38 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright 2025 Google LLC.
> + */
> +
> +#include "mode_selection.h"
> +#include "class.h"
> +#include "bus.h"
> +
> +static int increment_duplicated_priority(struct device *dev, void *data)
> +{
> +	struct typec_altmode **alt_target = (struct typec_altmode **)data;
> +
> +	if (is_typec_altmode(dev)) {
> +		struct typec_altmode *alt = to_typec_altmode(dev);
> +
> +		if (alt != *alt_target && alt->priority == (*alt_target)->priority) {
> +			alt->priority++;
> +			*alt_target = alt;
> +			return 1;

Couldn't you just always return 0?

> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +void typec_mode_set_priority(struct typec_altmode *alt,
> +		const unsigned int priority)
> +{
> +	struct typec_port *port = to_typec_port(alt->dev.parent);
> +	int res = 1;
> +
> +	alt->priority = priority;
> +
> +	while (res)
> +		res = device_for_each_child(&port->dev, &alt,
> +				increment_duplicated_priority);

Then this could be:

        device_for_each_child(&port->dev, &alt, increment_duplicated_priority);

right?

> +}
> diff --git a/drivers/usb/typec/mode_selection.h b/drivers/usb/typec/mode_selection.h
> new file mode 100644
> index 000000000000..cbf5a37e6404
> --- /dev/null
> +++ b/drivers/usb/typec/mode_selection.h
> @@ -0,0 +1,6 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#include <linux/usb/typec_altmode.h>
> +
> +void typec_mode_set_priority(struct typec_altmode *alt,
> +		const unsigned int priority);
> diff --git a/include/linux/usb/typec_altmode.h b/include/linux/usb/typec_altmode.h
> index b3c0866ea70f..571c6e00b54f 100644
> --- a/include/linux/usb/typec_altmode.h
> +++ b/include/linux/usb/typec_altmode.h
> @@ -28,6 +28,7 @@ struct typec_altmode {
>  	int				mode;
>  	u32				vdo;
>  	unsigned int			active:1;
> +	unsigned int			priority;
>  
>  	char				*desc;
>  	const struct typec_altmode_ops	*ops;
> -- 
> 2.51.0.rc2.233.g662b1ed5c5-goog
> 

-- 
heikki
Re: [PATCH v2 4/5] usb: typec: Implement alternate mode priority handling
Posted by Andrei Kuchynski 5 months, 1 week ago 
On Fri, Sep 5, 2025 at 12:25 PM Heikki Krogerus
<heikki.krogerus@linux.intel.com> wrote:
>
> On Mon, Aug 25, 2025 at 02:57:49PM +0000, Andrei Kuchynski wrote:
> > This patch introduces APIs to manage the priority of USB Type-C alternate
> > modes. These APIs allow for setting and retrieving a priority number for
> > each mode. If a new priority value conflicts with an existing mode's
> > priority, the priorities of the conflicting mode and all subsequent modes
> > are automatically incremented to ensure uniqueness.
> >
> > Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
> > ---
> >  drivers/usb/typec/Makefile         |  2 +-
> >  drivers/usb/typec/mode_selection.c | 38 ++++++++++++++++++++++++++++++
> >  drivers/usb/typec/mode_selection.h |  6 +++++
> >  include/linux/usb/typec_altmode.h  |  1 +
> >  4 files changed, 46 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/usb/typec/mode_selection.c
> >  create mode 100644 drivers/usb/typec/mode_selection.h
> >
> > diff --git a/drivers/usb/typec/Makefile b/drivers/usb/typec/Makefile
> > index 7a368fea61bc..8a6a1c663eb6 100644
> > --- a/drivers/usb/typec/Makefile
> > +++ b/drivers/usb/typec/Makefile
> > @@ -1,6 +1,6 @@
> >  # SPDX-License-Identifier: GPL-2.0
> >  obj-$(CONFIG_TYPEC)          += typec.o
> > -typec-y                              := class.o mux.o bus.o pd.o retimer.o
> > +typec-y                              := class.o mux.o bus.o pd.o retimer.o mode_selection.o
> >  typec-$(CONFIG_ACPI)         += port-mapper.o
> >  obj-$(CONFIG_TYPEC)          += altmodes/
> >  obj-$(CONFIG_TYPEC_TCPM)     += tcpm/
> > diff --git a/drivers/usb/typec/mode_selection.c b/drivers/usb/typec/mode_selection.c
> > new file mode 100644
> > index 000000000000..2179bf25f5d4
> > --- /dev/null
> > +++ b/drivers/usb/typec/mode_selection.c
> > @@ -0,0 +1,38 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Copyright 2025 Google LLC.
> > + */
> > +
> > +#include "mode_selection.h"
> > +#include "class.h"
> > +#include "bus.h"
> > +
> > +static int increment_duplicated_priority(struct device *dev, void *data)
> > +{
> > +     struct typec_altmode **alt_target = (struct typec_altmode **)data;
> > +
> > +     if (is_typec_altmode(dev)) {
> > +             struct typec_altmode *alt = to_typec_altmode(dev);
> > +
> > +             if (alt != *alt_target && alt->priority == (*alt_target)->priority) {
> > +                     alt->priority++;
> > +                     *alt_target = alt;
> > +                     return 1;
>
> Couldn't you just always return 0?
>

Priority values for each mode are consistently unique, eliminating the need
for further processing if a duplicate is found.

> > +             }
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +void typec_mode_set_priority(struct typec_altmode *alt,
> > +             const unsigned int priority)
> > +{
> > +     struct typec_port *port = to_typec_port(alt->dev.parent);
> > +     int res = 1;
> > +
> > +     alt->priority = priority;
> > +
> > +     while (res)
> > +             res = device_for_each_child(&port->dev, &alt,
> > +                             increment_duplicated_priority);
>
> Then this could be:
>
>         device_for_each_child(&port->dev, &alt, increment_duplicated_priority);
>
> right?
>

Unfortunately, the child's list is not in prioritized order. When a
duplicated value is found, the cycle should start for the whole list again.
I definitely need a loop here.

Thanks,
Andrei

Patchew 2.1-devel-b67e4c2

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