2018-01-27 17:26:36

by Sriram V

Subject: Purpose of line discipline in bt drivers

Hi,

I am facing broken audio issues when using the broadcom bt chip
especially when it comes back from suspend. While debugging the issue,

What is the purpose of doing a registering a ldisc in the driver using
the call tty_register_ldisc call() in Bluetooth drivers which deal
with power management.

I am referring to the below driver:
https://android.googlesource.com/kernel/bcm/+/android-4.4w_r6/drivers/misc/bcm-bt-lpm.c

Thanks for your help.
Sriram

2018-01-27 21:28:51

by Marcel Holtmann

Subject: Re: Purpose of line discipline in bt drivers

Hi Sriram,

> I am facing broken audio issues when using the broadcom bt chip
> especially when it comes back from suspend. While debugging the issue,
>
> What is the purpose of doing a registering a ldisc in the driver using
> the call tty_register_ldisc call() in Bluetooth drivers which deal
> with power management.
>
> I am referring to the below driver:
> https://android.googlesource.com/kernel/bcm/+/android-4.4w_r6/drivers/misc/bcm-bt-lpm.c

contact Broadcom about that driver or ask the Android team. It is not an upstream driver. Upstream uses hci_bcm.c which include proper power management and not some hacked up "stab you in the back” driver to make some userspace Bluetooth stack have access to hardware low power feature.

Regards

Marcel