> -----Original Message-----
> From: Greg KH [mailto:gre...@linuxfoundation.org]
> Sent: Monday, June 10, 2019 7:46 PM
> To: Mathias Nyman <mathias.ny...@linux.intel.com>
> Cc: Pandey, Prabhat Chand <prabhat.chand.pan...@intel.com>; linux-
> u...@vger.kernel.org; Nyman, Mathias <mathias.ny...@intel.com>;
> Regupathy, Rajaram <rajaram.regupa...@intel.com>; K V, Abhilash
> <abhilash....@intel.com>; Balaji, M <m.bal...@intel.com>
> Subject: Re: [PATCH 4/5] usb: xhci: dbc: Add a dbc raw driver to provide a raw
> interface on DbC
> Importance: High
>
> On Mon, Jun 10, 2019 at 04:53:51PM +0300, Mathias Nyman wrote:
> > On 7.6.2019 17.21, Greg KH wrote:
> > > On Fri, Jun 07, 2019 at 12:03:05PM +0530, Prabhat Chand Pandey wrote:
> > > > From: Abhilash K V <abhilash....@intel.com>
> > > >
> > > > This patch provides a raw device interface on xhci Debug capability.
> > >
> > > What is a "raw device"?
> > >
> > > > This abstracts dbc functionality to user space inorder to
> > > > facilitate various frameworks to utilize xhci debug capability.
> > >
> > > I do not understand this sentance at all. Please provide a lot more
> > > information.
> > >
> > > > It helps to render the target as an usb debug class device on host
> > > > and establish an usb connection by providing two bulk endpoints.
> > >
> > > provide bulk endpoints where? To send data where? This is very
> > > confusing and does not make any sense to me...
> > >
> > >
> > > >
> > > > [don't dynamically allocate tiny space for name only -Mathias]
> > > > Signed-off-by: Rajaram Regupathy <rajaram.regupa...@intel.com>
> > > > Signed-off-by: Prabhat Chand Pandey
> > > > <prabhat.chand.pan...@intel.com>
> > > > Signed-off-by: Abhilash K V <abhilash....@intel.com>
> > > > Acked-by: Mathias Nyman <mathias.ny...@linux.intel.com>
> > > > ---
> > ...
> > >
> > > So you have a new char device, with a undocumented and unknown
> > > format of data flowing across it to the device. How in the world
> > > are we supposed to use this thing? Where is it documented? What
> > > does it do? How can you use it?
We had captured all information in patch 5/5 patch in the documentation part.
We could always improve the documentation. Please let us know
> > >
> > > I don't mean to be so harsh here, but come on people, this stuff
> > > needs a lot more background documentation, information, and
> > > explaination as to exactly why in the world we need any of this, and what
> > > it
> even does!
> > >
> > > Also, you need to fix the code, it doesn't work as pointed out in a
> > > few places :)
> > >
> >
> > Thanks for going through this.
> > It's now clear this is far from ready.
> > I need to re-evaluate my position on this, not just the code and the
> > documentation, but the usefulness of it all.
>
> What is this even supposed to be used for? What is the application for it? I
> couldn't determine that at all, what am I missing?
A typical use case is ADB for x86 Android systems or similar user space
class(debug) drivers that can leverage xHCI.DbC capability for debug purpose.
The larger goal here is to have DbC as a unified debug infrastructure for
different debug methods like KGDB or early printk and leverage the benefits of
a dedicated debug infra (DbC) brings in.
>
> thanks,
>
> greg k-h
