From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg KH Subject: Re: [PATCH 2/4] misc: xgene: Add base driver for APM X-Gene SoC Queue Manager/Traffic Manager Date: Sat, 21 Dec 2013 17:01:29 -0800 Message-ID: <20131222010129.GA16366@kroah.com> References: <1387507503-7565-1-git-send-email-rapatel@apm.com> <1387507503-7565-3-git-send-email-rapatel@apm.com> <20131220032133.GB32310@kroah.com> <20131220042426.GA21726@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Ravi Patel Cc: Arnd Bergmann , davem@davemloft.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, jcm@redhat.com, "patches@apm.com" , Keyur Chudgar List-Id: devicetree@vger.kernel.org On Sat, Dec 21, 2013 at 04:43:06PM -0800, Ravi Patel wrote: > > On Thu, Dec 19, 2013 at 07:41:13PM -0800, Ravi Patel wrote: > >> There is no need to talk to this driver from userspace. > >> It is a device which is used by other IO devices to communicate with each > >> other, including CPU. > >> For example, if CPU (software) wants to send a message to Ethernet HW (i.e. > >> send packet), > >> it used this driver to enqueue a message to Ethernet. > >> In other direction, if Ethernet HW receives a packet, it uses QM/TM device to > >> send message to > >> CPU (software) to process packet. > > > > So it's a "bus" type of thing, right? > > > > My question of "why isn't this reflected in the driver model" still > > stands. > > There is no subsystem underneath QMTM, nor QMTM does any enumeration. > QMTM is a centralized resource manager which manages queues circularly > for Ethernet, PktDMA (XOR Engine) and Security Engine subsystems. > Traffic Management feature of QMTM does flow control, QoS for the subsystems. > Because of this reasons, its not obvious that QMTM can fit as a bus. > However we are doing further evalution on this. Just because you can't enumerate a device, doesn't mean it isn't a "bus". You say so yourself that this is how devices talk to the hardware, so that sounds like a "bus" to me... greg k-h