Re: [PATCH v6 1/8] usb: typec: Add default HPD device when register DisplayPort altmode

[Chaoyi Chen <chaoyi.chen@rock-chips.com>]

On 10/21/2025 4:48 PM, Heikki Krogerus wrote:

> Hi,
>
> On Mon, Oct 20, 2025 at 07:07:46PM +0800, Chaoyi Chen wrote:
>> Hi Heikki,
>>
>> On 10/20/2025 6:02 PM, Heikki Krogerus wrote:
>>> On Thu, Oct 16, 2025 at 10:27:34AM +0800, Chaoyi Chen wrote:
>>>> From: Chaoyi Chen <chaoyi.chen@rock-chips.com>
>>>>
>>>> Add default DRM AUX HPD bridge device when register DisplayPort
>>>> altmode. That makes it redundant for each Type-C driver to implement
>>>> a similar registration process in embedded scenarios.
>>>>
>>>> Signed-off-by: Chaoyi Chen <chaoyi.chen@rock-chips.com>
>>>> ---
>>>>
>>>> Changes in v6:
>>>> - Fix depend in Kconfig.
>>>>
>>>> Changes in v5:
>>>> - Remove the calls related to `drm_aux_hpd_bridge_notify()`.
>>>> - Place the helper functions in the same compilation unit.
>>>> - Add more comments about parent device.
>>>>
>>>>    drivers/usb/typec/Kconfig         |  2 ++
>>>>    drivers/usb/typec/class.c         | 26 ++++++++++++++++++++++++++
>>>>    include/linux/usb/typec_altmode.h |  2 ++
>>>>    3 files changed, 30 insertions(+)
>>>>
>>>> diff --git a/drivers/usb/typec/Kconfig b/drivers/usb/typec/Kconfig
>>>> index 2f80c2792dbd..a6730fbb576b 100644
>>>> --- a/drivers/usb/typec/Kconfig
>>>> +++ b/drivers/usb/typec/Kconfig
>>>> @@ -2,6 +2,8 @@
>>>>    menuconfig TYPEC
>>>>    	tristate "USB Type-C Support"
>>>> +	depends on DRM || DRM=n
>>>> +	select DRM_AUX_HPD_BRIDGE if DRM_BRIDGE && OF
>>> This is wrong. DRM should not dictate how this entire subsystem core
>>> is configured. The dependency needs to be on the DRM bridge side.
>>>
>>> You can for example use the bus notification there to see when a new
>>> alternate mode is being registered, or use some other notification
>>> mechanism.
>> Is it a good idea to implement notification functions like
>> drivers/usb/core/notify.c in TCPM, and then let other subsystems (such as DRM)
>> listen to these notifications?
> Don't limit this to tcpm only. I would suggest something similar what
> we have for usb bus: drivers/usb/core/notify.c
>
> So that, but for the typec bus. Then in DRM bridge code you just use
> typec_register/unregister_notify().

I will try to add drivers/usb/typec/notify.c in v7 to implement this. Thank you.


>
> thanks,
>
-- 
Best,
Chaoyi