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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 E606DC433DF for ; Mon, 19 Oct 2020 07:55:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8DF0922243 for ; Mon, 19 Oct 2020 07:55:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728009AbgJSHzp (ORCPT ); Mon, 19 Oct 2020 03:55:45 -0400 Received: from mga09.intel.com ([134.134.136.24]:55908 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727420AbgJSHzo (ORCPT ); Mon, 19 Oct 2020 03:55:44 -0400 IronPort-SDR: OpQOdNiXvLDW/sWnmSUEZk9sxmSmS2FfYTlYFhhminVkB/Ofc5jT59F/9cNlH0mq6exL5FXAkx ZlEgbpISviSQ== X-IronPort-AV: E=McAfee;i="6000,8403,9778"; a="167101322" X-IronPort-AV: E=Sophos;i="5.77,394,1596524400"; d="scan'208";a="167101322" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 Oct 2020 00:55:42 -0700 IronPort-SDR: ZD1cm0C3tCiHhoLCaYKfEalY1mMSkTbel5V33l9Br86FINuvC76hKRmBpkywkO6+BBvQIVBPaK owFvNIdaTxLg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.77,394,1596524400"; d="scan'208";a="347341205" Received: from yilunxu-optiplex-7050.sh.intel.com (HELO localhost) ([10.239.159.141]) by fmsmga004.fm.intel.com with ESMTP; 19 Oct 2020 00:55:40 -0700 Date: Mon, 19 Oct 2020 15:50:32 +0800 From: Xu Yilun To: "Wu, Hao" Cc: Tom Rix , "mdf@kernel.org" , "linux-fpga@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "gregkh@linuxfoundation.org" , "lgoncalv@redhat.com" , yilun.xu@intel.com Subject: Re: [PATCH 1/2] fpga: dfl: add driver_override support Message-ID: <20201019075032.GA28746@yilunxu-OptiPlex-7050> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Precedence: bulk List-ID: X-Mailing-List: linux-fpga@vger.kernel.org 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. > > 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. Thanks, Yilun > > Hao > > > > > > > +device_unlock(dev); > > > > +return len; > > > > +} > > > > + > > > > +static ssize_t driver_override_store(struct device *dev, > > > > + struct device_attribute *attr, > > > > + const char *buf, size_t count) > > > > +{ > > > > +struct dfl_device *ddev = to_dfl_dev(dev); > > > > +char *driver_override, *old, *cp; > > > > + > > > > +/* We need to keep extra room for a newline */ > > > > +if (count >= (PAGE_SIZE - 1)) > > > > +return -EINVAL; > > > > + > > > > +driver_override = kstrndup(buf, count, GFP_KERNEL); > > > > +if (!driver_override) > > > > +return -ENOMEM; > > > > + > > > > +cp = strchr(driver_override, '\n'); > > > > +if (cp) > > > > +*cp = '\0'; > > > > + > > > > +device_lock(dev); > > > > +old = ddev->driver_override; > > > > +if (strlen(driver_override)) { > > > > +ddev->driver_override = driver_override; > > > > +} else { > > > > +kfree(driver_override); > > > > +ddev->driver_override = NULL; > > > > +} > > > > +device_unlock(dev); > > > > + > > > > +kfree(old); > > > > + > > > > +return count; > > > > +} > > > > +static DEVICE_ATTR_RW(driver_override); > > > > + > > > > static ssize_t > > > > type_show(struct device *dev, struct device_attribute *attr, char *buf) > > > > { > > > > @@ -324,6 +375,7 @@ static DEVICE_ATTR_RO(feature_id); > > > > static struct attribute *dfl_dev_attrs[] = { > > > > &dev_attr_type.attr, > > > > &dev_attr_feature_id.attr, > > > > +&dev_attr_driver_override.attr, > > > > NULL, > > > > }; > > > > ATTRIBUTE_GROUPS(dfl_dev); > > > > @@ -469,7 +521,7 @@ static int dfl_devs_add(struct > > dfl_feature_platform_data *pdata) > > > > > > > > int __dfl_driver_register(struct dfl_driver *dfl_drv, struct module *owner) > > > > { > > > > -if (!dfl_drv || !dfl_drv->probe || !dfl_drv->id_table) > > > > +if (!dfl_drv || !dfl_drv->probe) > > > > > > id_table is still needed for the normal case. > > > > > > Instead of removing this check, could you add something like > > > > > > || (!dfl_drv->is_override && !dfl_drv->id_table) > > > > I don't think it is needed. Seems is_override and !id_table are duplicated > > conditions for this implementation. And it may make confusing, e.g. could > > a driver been force matched when is_override is not set? > > > > I think we could make it simple, if the dfl driver didn't provide the > > id_table, normally it could not match any device. I think it could be > > easily understood by dfl driver developers. > > > > > > Thanks, > > Yilun > > > > > > > > Tom > > > > > > > return -EINVAL; > > > > > > > > dfl_drv->drv.owner = owner; > > > > diff --git a/include/linux/dfl.h b/include/linux/dfl.h > > > > index 7affba2f..e1b2471 100644 > > > > --- a/include/linux/dfl.h > > > > +++ b/include/linux/dfl.h > > > > @@ -32,6 +32,7 @@ enum dfl_id_type { > > > > * @num_irqs: number of IRQs supported by this dfl device. > > > > * @cdev: pointer to DFL FPGA container device this dfl device belongs to. > > > > * @id_entry: matched id entry in dfl driver's id table. > > > > + * @driver_override: driver name to force a match > > > > */ > > > > struct dfl_device { > > > > struct device dev; > > > > @@ -43,6 +44,7 @@ struct dfl_device { > > > > unsigned int num_irqs; > > > > struct dfl_fpga_cdev *cdev; > > > > const struct dfl_device_id *id_entry; > > > > +char *driver_override; > > > > }; > > > > > > > > /**