From: Sarah Sharp <sarah.a.sharp@linux.intel.com>
To: shashank chaturvedi <chaturvedi9950@gmail.com>
Cc: linux-usb@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: xhci Portsc register issue
Date: Fri, 26 Oct 2012 10:17:42 -0700 [thread overview]
Message-ID: <20121026171742.GF4713@xanatos> (raw)
In-Reply-To: <CALuomMs-Z_PH3KpEPDgjBr5oy86Go2G2PAxu_k2yxgzWwRhJYQ@mail.gmail.com>
On Fri, Oct 26, 2012 at 10:32:05AM +0530, shashank chaturvedi wrote:
> >Why would you want to do that? For link power management? What is the
> >xHCI kernel driver not providing you such that you have to write a
> >userspace program?
>
> I want to do this for link power managment.But i am able to read & write
> the PORTPMSC register (as per xhci spec 5.4.9) from userspace program.Why
> not the PORTSC regsiter?
Do NOT do this from userspace! You need to modify the xHCI kernel
driver to support link PM for your host controller. The USB core has
specific times it disables link PM (e.g. before a device is reset) and
some drivers may require link PM to be disabled. You are circumventing
kernel policy by writing the link PM registers from userspace. Do NOT
do this!
Sarah Sharp
next prev parent reply other threads:[~2012-10-26 17:17 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CALuomMuUD4xSaCUT6MZn3ZV2gjXnuBUhkz78PgXZ6XgV4e-NvA@mail.gmail.com>
2012-10-25 15:36 ` xhci Portsc register issue Sarah Sharp
2012-10-25 16:45 ` Bjorn Helgaas
2012-10-25 22:37 ` Peter Stuge
[not found] ` <CALuomMs-Z_PH3KpEPDgjBr5oy86Go2G2PAxu_k2yxgzWwRhJYQ@mail.gmail.com>
2012-10-26 17:17 ` Sarah Sharp [this message]
2012-10-26 7:12 ` Gerd Hoffmann
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