From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755419AbdEHUpA (ORCPT ); Mon, 8 May 2017 16:45:00 -0400 Received: from mail.kernel.org ([198.145.29.136]:39674 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752402AbdEHUo6 (ORCPT ); Mon, 8 May 2017 16:44:58 -0400 MIME-Version: 1.0 In-Reply-To: References: <1492697401-11211-1-git-send-email-atull@kernel.org> <1492697401-11211-3-git-send-email-atull@kernel.org> <20170503115831.GA30448@hao-dev> From: Alan Tull Date: Mon, 8 May 2017 15:44:12 -0500 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v2 02/16] fpga: bridge: support getting bridge from device To: "Wu, Hao" Cc: Moritz Fischer , linux-kernel , "linux-fpga@vger.kernel.org" , "matthew.gerlach@linux.intel.com" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 8, 2017 at 3:44 AM, Wu, Hao wrote: >> On Wed, May 3, 2017 at 3:07 PM, Alan Tull wrote: >> > On Wed, May 3, 2017 at 6:58 AM, Wu Hao wrote: >> >> On Thu, Apr 20, 2017 at 09:09:47AM -0500, Alan Tull wrote: >> >>> Add two functions for getting the FPGA bridge from the device >> >>> rather than device tree node. This is to enable writing code >> >>> that will support using FPGA bridges without device tree. >> >>> Rename one old function to make it clear that it is device >> >>> tree-ish. This leaves us with 3 functions for getting a bridge: >> >>> >> >>> * fpga_bridge_get >> >>> Get the bridge given the device. >> >>> >> >>> * fpga_bridges_get_to_list >> >>> Given the device, get the bridge and add it to a list. >> >>> >> >>> * of_fpga_bridges_get_to_list >> >>> Renamed from priviously existing fpga_bridges_get_to_list. >> >>> Given the device node, get the bridge and add it to a list. >> >>> >> >> >> >> Hi Alan >> >> >> >> Thanks a lot for providing this patch set for non device tree support. :) >> >> Actually I am reworking the Intel FPGA device drivers based on this patch >> >> set, and I find some problems with the existing APIs including fpga bridge >> >> and manager. My idea is to create all fpga bridges/regions/manager under >> >> the same platform device (FME), it allows FME driver to establish the >> >> relationship for the bridges/regions/managers it creates in an easy way. >> >> But I found current fpga class API doesn't support this very well. >> >> e.g fpga_bridge_get/get_to_list only accept parent device as the input >> >> parameter, but it doesn't work if we have multiple bridges (and >> >> regions/manager) under the same platform device. fpga_mgr has similar >> >> issue, but fpga_region APIs work better, as they accept fpga_region as >> >> parameter not the shared parent device. >> > >> > That's good feedback. I can post a couple patches that apply on top >> > of that patchset to add the APIs you need. >> > >> > Probably what I'll do is add >> > >> > struct fpga_manager *fpga_mgr_get(struct fpga_manager *mgr); >> > >> > And rename fpga_bridge_get() to fpga_bridge_dev_get() and add the >> following: >> > >> > struct fpga_bridge *fpga_bridge_get(struct fpga_bridge *br, >> > struct fpga_image_info *info); >> > >> > int of_fpga_bridge_get_to_list(struct fpga_bridge *br, >> > struct fpga_image_info *info, >> > struct list_head *bridge_list); >> > >> > Working on it now. >> > >> >> >> >> Do you think if having multiple fpga-* under one parent device is in the >> >> right direction? >> > >> > That should be fine as long as it's coded with an eye on making things >> > reusable and seeing beyond the current project. Just thinking of the >> > future and of what can be of general usefulness for others. And there >> > will be others interested in reusing this. >> > >> > Alan >> >> Actually, I don't think you will need the additional APIs we were >> just discussing after all. What you have is a multifunction device >> (single piece of hardware, multi functions such as in drivers/mfd). >> It will have child devices for the mgr, bridges, and regions. When >> registering the mgr and bridges you will need to allocate child >> devices and use them to create the mgr and bridges. >> >> Alan > > Hi Alan > > I tried to create child devices as the parent device for the mgr and > bridges in fme platform driver module. If only creates the device without > driver, it doesn't work as try_module_get(dev->parent->driver->owner) > always failed in mgr_get and bridge_get functions. I tried it and it wasn't hard. Each mgr or bridge driver should be a separate file which registers its driver using 'module_platform_driver". That way the drivers are registered with the kernel in a normal fashion. The thing we want here is to not bypass the kernel driver model. You'll need to keep the platform_device pointers in private data somewhere. For each child platform device, do a platform_device_alloc and platform_device_add. Then to get the manager, you can do mgr = fpga_mgr_get(&priv->mgr_pdev->dev); If this is in your probe function, you can use -EPROBE_DEFER if platform_device_alloc or fpga_mgr_get fail. Then you could destroy whatever you've created and return -EPROBE_DEFER to wait for the drivers you need to be registered and ready for devices to be added. > > If it creates platform devices as child devices, and introduce new platform > device drivers for bridge and mgr, then it will be difficult to establish the > relationship for region/mgr/bridges (e.g when should region->mgr be > configured and cleared, as mgr is created/destroyed when mgr parent > device platform driver module is loaded/unload), and it maybe not really > necessary to introduce more different driver modules here. It should be pretty easy to create/destroy child devices as shown above. The kernel does this all the time. > > But if it allows multiple fpga-* created under one device in one device > driver, it will be much easier to avoid above problems. So I asked if it > is possible to create multiple fpga-* under one parent device, I think it's fine for your FME to create child platform devices. It's similar to a mfd, but the mfd framework hides the platform devices from the module that creates them, unfortunately. > I feel > this will not impact to current fpga drivers a lot, but provide more > flexibility for drivers to use fpga-region/bridge/manager to create > the topology in a device specific way, especially for non device > tree case. > I would like to see most of this code as FME enumeration code + a mgr driver + a bridge driver + a region driver. If the FME and the enumeration code can be separate files, so much the better for general usability. The enumeration code can build a set of regions by doing something like this: 1. figure out what type of mgr and bridges your hardware FME has. 2. do platform_device_alloc and platform_device_add to create the mgr device, save a pointer to its platform_device in your FME driver's private data. 2. For each port, create a region and a bridge device. Save the region's platform device or struct in a list in your FME driver's priv. 3. then you can create the sub function devices. > Thanks > Hao