On 29.08.2016 08:26, Lu Baolu wrote:
xHCI debug capability (DbC) is an optional but standalone
functionality provided by an xHCI host controller. With DbC
hardware initialized, the system will present a debug device
through the USB3 debug port (normally the first USB3 port).
The debug device is fully compliant with the USB framework
and provides the equivalent of a very high performance (USB3)
full-duplex serial link between the debug host and target.
The DbC functionality is independent of xHCI host. There
isn't any precondition from xHCI host side for DbC to work.

This patch set adds support for early printk functionality
through a USB3 debug port by 1) initializing and enabling
the DbC hardware during early boot; 2) registering a boot
console to the system so that early printk messages can go
through the USB3 debug port. It also includes some lines
of changes in usb_debug driver so that it can be bound when
a USB3 debug device is enumerated.

This is the resend version. Original patch set was submitted
several months ago. This resend version addresses the review
comment here [1].

[1] https://lkml.org/lkml/2016/2/16/444

So other than making sure memory is freed,
(and maybe cleanup the duplicate code) I don't really have any objections.

As you state in PATCH 1/4, this could be useful in the specific case of
kernel debugging when machine crashes very early before the console code is
initialized. For normal operation it is not recommended.

And as it's not recommended or used for normal operations it shouldn't do any
harm either

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