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[75.142.250.213]) by smtp.gmail.com with ESMTPSA id l125sm52560qke.23.2020.10.19.06.55.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 19 Oct 2020 06:55:59 -0700 (PDT) Subject: Re: [PATCH 1/2] fpga: dfl: add driver_override support To: Xu Yilun Cc: mdf@kernel.org, linux-fpga@vger.kernel.org, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, lgoncalv@redhat.com, hao.wu@intel.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> From: Tom Rix Message-ID: Date: Mon, 19 Oct 2020 06:55:57 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20201019040612.GA16172@yilunxu-OptiPlex-7050> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-fpga@vger.kernel.org On 10/18/20 9:06 PM, Xu Yilun 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.' yes, this is good. > >> >>> 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. I am not sure if you are agreeing to do this change. I was looking at the other driver_override_show() functions. Generally the 'n' variants of string functions should be used. > >>> + 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. > Then an ASSERT should be added in dfl_bus_match() for id_entry. Tom > 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; >>> }; >>> >>> /**