Re: [PATCH v4 0/5] This series is split from the v15 "Add Type-C DP support for RK3399 EVB

[Chaoyi Chen]

Hi Sebastian,

On 7/28/2026 6:44 PM, Sebastian Reichel wrote:
> Hello Chaoyi,
> 
> On Tue, Jul 28, 2026 at 10:33:48AM +0800, Chaoyi Chen wrote:
>>>> Changes in v4:
>>>> - Link to v3: https://lore.kernel.org/all/20260717072323.96-1-kernel@xxxxxxxxxx/
>>>> - Scan the entire typec_bus and attempt to register the hpd bridge,
>>>>   so as not to miss devices that were already added during initialization.
>>>
>>> While that may help with the module being loaded late, it does not
>>> help with triggering the module load in the first place.
>>>
>>> The module does not have any MODULE_DEVICE_TABLE() helping with
>>> that. So basically any system relying on the automatic hpd bridge
>>> registration and using a modular kernel (e.g. the arm64 defconfig or
>>> the kernels usually provided by Linux distributions) requires
>>> manually loading that module to get any graphical output.
>>>
>>
>> Thank you for pointing this out. I will add it in v5.
> 
> Add what exactly? As this code is quite generic, you don't have
> anything for a MODULE_DEVICE_TABLE() (i.e. no OF, no I2C, ...).
> 

That is:

static const struct typec_device_id dp_typec_id[] = {
	{ USB_TYPEC_DP_SID },
	{ },
};
MODULE_DEVICE_TABLE(typec, dp_typec_id);

Just like the modules in drivers/usb/typec/altmodes/ .

> One solution I see to keep the notifier design would be to add
> 
> MODULE_SOFTDEP("pre: aux-hpd-typec-dp-bridge")
> 
> to some other module and piggy-back on it. Alternatively integrate
> it directly to some other module, such as "drm_display_helper",
> which already has DRM_DISPLAY_DP_HELPER and DRM_DISPLAY_DP_TUNNEL.
> Adding TypeC DP AltMode as part of it seems sensible to me.
>

I agree, placing it on the DRM side looks more reasonable.

> FWIW I suggest you test booting your patches work with the arm64
> defconfig before your next submission ;)
>

Oh, I will. It's just that I've always been using buildroot. I'll check 
the situation with other distributions.


> Greetings,
> 
> -- Sebastian

-- 
Best, 
Chaoyi