Re: [PATCH 3/3] usb: typec: altmodes/displayport: Notify drm subsys of hotplug events

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Mon, Feb 25, 2019 at 02:20:37PM +0100, Hans de Goede wrote:
> Use the new drm_kms_call_oob_hotplug_notifier_chain() function to load
> drm/kms drivers know about DisplayPort over Type-C hotplug events.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  drivers/usb/typec/altmodes/displayport.c | 34 ++++++++++++++++--------
>  1 file changed, 23 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
> index 35161594e368..87760ea252d6 100644
> --- a/drivers/usb/typec/altmodes/displayport.c
> +++ b/drivers/usb/typec/altmodes/displayport.c
> @@ -13,6 +13,7 @@
>  #include <linux/module.h>
>  #include <linux/usb/pd_vdo.h>
>  #include <linux/usb/typec_dp.h>
> +#include <drm/drm_probe_helper.h>
>  
>  #define DP_HEADER(cmd)			(VDO(USB_TYPEC_DP_SID, 1, cmd) | \
>  					 VDO_OPOS(USB_TYPEC_DP_MODE))
> @@ -67,12 +68,23 @@ struct dp_altmode {
>  	const struct typec_altmode *port;
>  };
>  
> -static int dp_altmode_notify(struct dp_altmode *dp)
> +static int dp_altmode_notify(struct dp_altmode *dp, unsigned long conf)
> +{
> +	int ret;
> +
> +	ret = typec_altmode_notify(dp->alt, conf, &dp->data);
> +	if (ret)
> +		return ret;
> +
> +	drm_kms_call_oob_hotplug_notifier_chain(DRM_OOB_HOTPLUG_TYPE_C_DP);

Is this causing a build/run-time dependancy of the USB code on DRM now?
What about typec systems without DRM, is that a thing?

I have no objection to this if the DRM people like this type of api
(personally I hate notifier chains), just curious about the dependancy
issues involved.

thanks,

greg k-h
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