From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6F81EC433E7 for ; Mon, 19 Oct 2020 08:53:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 173D222268 for ; Mon, 19 Oct 2020 08:53:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603097595; bh=1OYAqCqBOwKL+mF0SHedq9tIVQFamriaxmYZcZAS80k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=rdJigahQnmJv0hKVQFXn6HRTYM/ygxcLzvnGXfsssYI6xBKvMLBJjmWv9MU47zg5M 5GSuX+M0Nhgwtp9Wchlxs4S8/lyJJ2Xh8CkmJgkQS0uR0RtVxJjo72NOPFFTB+kV4A LlQYms+7K4nzpLyOqpYmaJh8pMsFpVIV48Vbp75k= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729578AbgJSIxO (ORCPT ); Mon, 19 Oct 2020 04:53:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:35152 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729287AbgJSIxO (ORCPT ); Mon, 19 Oct 2020 04:53:14 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 96A9F20790; Mon, 19 Oct 2020 08:53:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603097593; bh=1OYAqCqBOwKL+mF0SHedq9tIVQFamriaxmYZcZAS80k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=hOPSYRIOpPuOd8ghkXWMl+hUGQuONETBWdG7slsW2Nof/BzKx9dxehJO5TSZttktX ASsuEUhHLaBQ6NxbMQ3DqdLPLsz9fyXSnYsgBDleK8cqYs3DU65utLvYO4RoRxotSY P5qnIyXwpglNVFykG1ku38rKNC/Ruytoil6qlHmY= Date: Mon, 19 Oct 2020 10:53:57 +0200 From: "gregkh@linuxfoundation.org" To: Xu Yilun Cc: "Wu, Hao" , Tom Rix , "mdf@kernel.org" , "linux-fpga@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "lgoncalv@redhat.com" Subject: Re: [PATCH 1/2] fpga: dfl: add driver_override support Message-ID: <20201019085357.GA3235300@kroah.com> References: <1602828151-24784-1-git-send-email-yilun.xu@intel.com> <1602828151-24784-2-git-send-email-yilun.xu@intel.com> <63d7730b-d9b8-c75d-16f6-3ebb507aabaa@redhat.com> <20201019040612.GA16172@yilunxu-OptiPlex-7050> <20201019075032.GA28746@yilunxu-OptiPlex-7050> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201019075032.GA28746@yilunxu-OptiPlex-7050> Precedence: bulk List-ID: X-Mailing-List: linux-fpga@vger.kernel.org On Mon, Oct 19, 2020 at 03:50:32PM +0800, Xu Yilun wrote: > On Mon, Oct 19, 2020 at 03:46:23PM +0800, Wu, Hao wrote: > > > On Fri, Oct 16, 2020 at 09:21:50AM -0700, Tom Rix wrote: > > > > > > > > On 10/15/20 11:02 PM, Xu Yilun wrote: > > > > > Add support for overriding the default matching of a dfl device to a dfl > > > > > driver. It follows the same way that can be used for PCI and platform > > > > > devices. This patch adds the 'driver_override' sysfs file. > > > > > > > > > > Signed-off-by: Xu Yilun > > > > > --- > > > > > Documentation/ABI/testing/sysfs-bus-dfl | 28 ++++++++++++++--- > > > > > drivers/fpga/dfl.c | 54 > > > ++++++++++++++++++++++++++++++++- > > > > > include/linux/dfl.h | 2 ++ > > > > > 3 files changed, 79 insertions(+), 5 deletions(-) > > > > > > > > > > diff --git a/Documentation/ABI/testing/sysfs-bus-dfl > > > b/Documentation/ABI/testing/sysfs-bus-dfl > > > > > index 23543be..db7e8d3 100644 > > > > > --- a/Documentation/ABI/testing/sysfs-bus-dfl > > > > > +++ b/Documentation/ABI/testing/sysfs-bus-dfl > > > > > @@ -1,15 +1,35 @@ > > > > > What:/sys/bus/dfl/devices/dfl_dev.X/type > > > > > -Date:Aug 2020 > > > > > -KernelVersion:5.10 > > > > > +Date:Oct 2020 > > > > > +KernelVersion:5.11 > > > > > Contact:Xu Yilun > > > > > Description:Read-only. It returns type of DFL FIU of the device. > > > Now DFL > > > > > supports 2 FIU types, 0 for FME, 1 for PORT. > > > > > Format: 0x%x > > > > > > > > > > What:/sys/bus/dfl/devices/dfl_dev.X/feature_id > > > > > -Date:Aug 2020 > > > > > -KernelVersion:5.10 > > > > > +Date:Oct 2020 > > > > > +KernelVersion:5.11 > > > > > Contact:Xu Yilun > > > > > Description:Read-only. It returns feature identifier local to its DFL > > > FIU > > > > > type. > > > > > Format: 0x%x > > > > > > > > These updates, do not match the comment. > > > > > > > > Consider splitting this out. > > > > > > I'm sorry it's a typo. The above code should not be changed. > > > > > > > > > > > > + > > > > > +What: /sys/bus/dfl/devices/.../driver_override > > > > > +Date: Oct 2020 > > > > > +KernelVersion: 5.11 > > > > > +Contact: Xu Yilun > > > > I am looking at description and trying to make it consistent with sysfs-bus- > > > pci > > > > > +Description: This file allows the driver for a device to be specified. > > > > > > > > 'to be specified which will override the standard dfl bus feature id to driver > > > mapping.' > > > > > > Yes, it could be improved. > > > > > > Actually now it is the "type" and "feature id" matching, the 2 fields > > > are defined for dfl_driver.id_table. In future for dfl v1, it may be > > > GUID matching, which will be added to id_table. So how about we make it > > > more generic: > > > > > > 'to be specified which will override the standard ID table matching.' > > > > > > > > > > > > > > > > When > > > > > + specified, only a driver with a name matching the value written > > > > > + to driver_override will have an opportunity to bind to the > > > > > + device. The override is specified by writing a string to the > > > > > + driver_override file (echo dfl-uio-pdev > driver_override) and > > > > > + may be cleared with an empty string (echo > driver_override). > > > > > + This returns the device to standard matching rules binding. > > > > > + Writing to driver_override does not automatically unbind the > > > > > + device from its current driver or make any attempt to > > > > > + automatically load the specified driver. If no driver with a > > > > > + matching name is currently loaded in the kernel, the device > > > > > + will not bind to any driver. This also allows devices to > > > > > + opt-out of driver binding using a driver_override name such as > > > > > + "none". Only a single driver may be specified in the override, > > > > > + there is no support for parsing delimiters. > > > > > diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c > > > > > index 511b20f..bc35750 100644 > > > > > --- a/drivers/fpga/dfl.c > > > > > +++ b/drivers/fpga/dfl.c > > > > > @@ -262,6 +262,10 @@ static int dfl_bus_match(struct device *dev, > > > struct device_driver *drv) > > > > > struct dfl_driver *ddrv = to_dfl_drv(drv); > > > > > const struct dfl_device_id *id_entry; > > > > > > > > > > +/* When driver_override is set, only bind to the matching driver */ > > > > > +if (ddev->driver_override) > > > > > +return !strcmp(ddev->driver_override, drv->name); > > > > > + > > > > > id_entry = ddrv->id_table; > > > > > if (id_entry) { > > > > > while (id_entry->feature_id) { > > > > > @@ -303,6 +307,53 @@ static int dfl_bus_uevent(struct device *dev, > > > struct kobj_uevent_env *env) > > > > > ddev->type, ddev->feature_id); > > > > > } > > > > > > > > > > > > > I am looking at other implementations of driver_override* and looking for > > > consistency. > > > > > > > > > +static ssize_t driver_override_show(struct device *dev, > > > > > + struct device_attribute *attr, char *buf) > > > > > +{ > > > > > +struct dfl_device *ddev = to_dfl_dev(dev); > > > > > +ssize_t len; > > > > > + > > > > > +device_lock(dev); > > > > > +len = sprintf(buf, "%s\n", ddev->driver_override); > > > > len = snprintf(buf, PAGE_SIZE ... > > > > > > It is good to me. > > > > > > Some bus drivers use snprintf, some use sprintf. > > > > > > I think it is reasonable snprintf is used here, unlike %d, %u ... it is > > > uncertain for the output size of %s. No, no one should care at all about this. If you are caring, then you are using sysfs wrong. Just use sprintf(), you never care about the size of the buffer for a show/store function. Or better yet, use the new sysfs_emit() call, that is what everything will be converted over to anyway. > > you limited the size < a page in store function for driver_override? > > Yes. So normally the sprintf should be OK. But I think it may be safer > if the driver_override pointer is corrupted in some unexpected cases. How can that happen? greg k-h