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Date: Fri, 16 Oct 2020 09:21:50 -0700
From: Tom Rix <trix@...hat.com>
To: Xu Yilun <yilun.xu@...el.com>, mdf@...nel.org,
linux-fpga@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: gregkh@...uxfoundation.org, lgoncalv@...hat.com, hao.wu@...el.com
Subject: Re: [PATCH 1/2] fpga: dfl: add driver_override support
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 <yilun.xu@...el.com>
> ---
> 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 <yilun.xu@...el.com>
> 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 <yilun.xu@...el.com>
> 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.
> +
> +What: /sys/bus/dfl/devices/.../driver_override
> +Date: Oct 2020
> +KernelVersion: 5.11
> +Contact: Xu Yilun <yilun.xu@...el.com>
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.'
> 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 ...
> + 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)
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;
> };
>
> /**
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