From: Greg Kroah-Hartman Subject: Re: [PATCH v5 1/2] TTY: Add TTY slave enumeration support Date: Fri, 25 Jan 2013 16:21:47 -0800 Message-ID: <20130126002147.GA5132@kroah.com> References: <12848b50e1096dc11a193694ee248d51d45ce093.1359022955.git.lv.zheng@intel.com> <20130125214121.GA30924@kroah.com> <20130126003216.1f16a705@bob.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20130126003216.1f16a705@bob.linux.org.uk> Sender: linux-acpi-owner@vger.kernel.org To: Alan Cox Cc: Lv Zheng , Rafael J Wysocki , Len Brown , Mika Westerberg , linux-acpi@vger.kernel.org, linux-serial@vger.kernel.org List-Id: linux-serial@vger.kernel.org On Sat, Jan 26, 2013 at 12:32:16AM +0000, Alan Cox wrote: > > Or am I missing something big and major here? How have people been > > seeing and configuring their tty devices for the last 8+ years or so > > since the 2.6.0 kernel was released with uevent support for tty > > devices? > > Minor more than major. The newer ACPI tries to begin to describe what > is on the other end of serial busses being used for internal purposes. > > Now there are several good reasons we want to know what is on the end > of a port already that are not currently handled, and I have suggested > a port "type" attribute would be useful (eg unknown, modem, bluetooth, > ax25, dcc, etc) so the kernel can help user space enumerate in user > friendly fashion. That's fine, just add a single attribute to the existing tty class device, not a whole new class, which is what this code does. > Where it gets slightly more tricky is that we are beginning to see > systems where the firmware is describing > > serial port (and power management) > device behind port (and power management) > > so there is a power management hierarchy involved. Ick, that's going to get messy fast. There's no hope they would switch to a USB connection instead for these devices, could they? That would fix up most of these issues, and make the devices discoverable. thanks, greg k-h