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Date:   Tue, 15 Dec 2020 10:06:08 +0800
From:   Xu Yilun <yilun.xu@...el.com>
To:     Tom Rix <trix@...hat.com>
Cc:     mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        lgoncalv@...hat.com, hao.wu@...el.com
Subject: Re: [PATCH v2 1/2] fpga: dfl: add the userspace I/O device support
  for DFL devices

On Mon, Dec 14, 2020 at 02:03:03PM -0800, Tom Rix wrote:
> 
> 
> On 12/13/20 7:36 PM, Xu Yilun wrote:
> > This patch supports the DFL drivers be written in userspace. This is
> > realized by exposing the userspace I/O device interfaces.
> >
> > The driver leverages the uio_pdrv_genirq, it adds the uio_pdrv_genirq
> > platform device with the DFL device's resources, and let the generic UIO
> > platform device driver provide support to userspace access to kernel
> > interrupts and memory locations.
> >
> > The driver matches DFL devices in a different way. It has no device id
> > table, instead it matches any DFL device which could not be handled by
> > other DFL drivers. For this purpose, a match() ops is added to the dfl
> > driver, to allow dfl drivers have their own matching algorithem instead
> > of the standard id_table matching.
> 
> Because (*match) is added, this change is doing two things.
> 
> In the next version, please split the new interface out, i believe these are
> 
> the dfl.c/h changes.

Yes, I'll split it out.

> 
> >
> > Signed-off-by: Xu Yilun <yilun.xu@...el.com>
> > ---
> > v2: switch to the new matching algorithem. It matches DFL devices which
> >      could not be handled by other DFL drivers.
> >     refacor the code about device resources filling.
> >     fix some comments.
> > ---
> >  drivers/fpga/Kconfig        |  10 ++++
> >  drivers/fpga/Makefile       |   1 +
> >  drivers/fpga/dfl-uio-pdev.c | 108 ++++++++++++++++++++++++++++++++++++++++++++
> >  drivers/fpga/dfl.c          |  22 +++++++--
> >  include/linux/dfl.h         |   7 +++
> >  5 files changed, 143 insertions(+), 5 deletions(-)
> >  create mode 100644 drivers/fpga/dfl-uio-pdev.c
> >
> > diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
> > index 5d7f0ae..eb8a616 100644
> > --- a/drivers/fpga/Kconfig
> > +++ b/drivers/fpga/Kconfig
> > @@ -202,6 +202,16 @@ config FPGA_DFL_NIOS_INTEL_PAC_N3000
> >  	  the card. It also instantiates the SPI master (spi-altera) for
> >  	  the card's BMC (Board Management Controller).
> >  
> > +config FPGA_DFL_UIO_PDEV
> > +	tristate "FPGA DFL Driver for Userspace I/O platform devices"
> > +	depends on FPGA_DFL && UIO_PDRV_GENIRQ
> > +	help
> > +	  Enable this to allow some DFL drivers be written in userspace. It
> > +	  adds the uio_pdrv_genirq platform device with the DFL device's
> DFL feature's

Will change it.

> > +	  resources, and lets the generic UIO platform device driver provide
> > +	  support to userspace access to kernel interrupts and memory
> support for userspace

Will change it.

> > +	  locations.
> > +
> >  config FPGA_DFL_PCI
> >  	tristate "FPGA DFL PCIe Device Driver"
> >  	depends on PCI && FPGA_DFL
> > diff --git a/drivers/fpga/Makefile b/drivers/fpga/Makefile
> > index 18dc9885..e07b3d5 100644
> > --- a/drivers/fpga/Makefile
> > +++ b/drivers/fpga/Makefile
> > @@ -45,6 +45,7 @@ dfl-afu-objs := dfl-afu-main.o dfl-afu-region.o dfl-afu-dma-region.o
> >  dfl-afu-objs += dfl-afu-error.o
> >  
> >  obj-$(CONFIG_FPGA_DFL_NIOS_INTEL_PAC_N3000)	+= dfl-n3000-nios.o
> > +obj-$(CONFIG_FPGA_DFL_UIO_PDEV)	+= dfl-uio-pdev.o
> This does not really align with += dfl-pci.o, add another tab.

Will change it.

> >  
> >  # Drivers for FPGAs which implement DFL
> >  obj-$(CONFIG_FPGA_DFL_PCI)		+= dfl-pci.o
> > diff --git a/drivers/fpga/dfl-uio-pdev.c b/drivers/fpga/dfl-uio-pdev.c
> > new file mode 100644
> > index 0000000..68ede04
> > --- /dev/null
> > +++ b/drivers/fpga/dfl-uio-pdev.c
> > @@ -0,0 +1,108 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * DFL driver for Userspace I/O platform devices
> > + *
> > + * Copyright (C) 2020 Intel Corporation, Inc.
> > + */
> > +#include <linux/dfl.h>
> > +#include <linux/errno.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/slab.h>
> > +#include <linux/uio_driver.h>
> > +
> > +#define DRIVER_NAME "dfl-uio-pdev"
> > +
> > +static struct dfl_driver dfl_uio_pdev_driver;
> > +
> > +static int check_for_other_drv_match(struct device_driver *drv, void *data)
> > +{
> > +	struct dfl_driver *ddrv = to_dfl_drv(drv);
> > +	struct dfl_device *ddev = data;
> > +
> > +	/* skip myself */
> > +	if (ddrv == &dfl_uio_pdev_driver)
> > +		return 0;
> > +
> > +	return dfl_match_device(ddev, ddrv);
> > +}
> > +
> > +static int dfl_uio_pdev_match(struct dfl_device *ddev)
> > +{
> > +	/*
> > +	 * If any other driver wants the device, leave the device to this other
> > +	 * driver.
> > +	 */
> > +	if (bus_for_each_drv(&dfl_bus_type, NULL, ddev, check_for_other_drv_match))
> > +		return 0;
> > +
> > +	return 1;
> > +}
> > +
> > +static int dfl_uio_pdev_probe(struct dfl_device *ddev)
> > +{
> > +	struct device *dev = &ddev->dev;
> > +	struct platform_device_info pdevinfo = { 0 };
> > +	struct uio_info uio_pdata = { 0 };
> > +	struct platform_device *uio_pdev;
> > +	struct resource *res;
> > +	int i;
> > +
> > +	pdevinfo.name = "uio_pdrv_genirq";
> > +
> > +	res = kcalloc(ddev->num_irqs + 1, sizeof(*res), GFP_KERNEL);
> > +	if (!res)
> > +		return -ENOMEM;
> > +
> > +	res[0].parent = &ddev->mmio_res;
> > +	res[0].flags = IORESOURCE_MEM;
> > +	res[0].start = ddev->mmio_res.start;
> > +	res[0].end = ddev->mmio_res.end;
> > +
> > +	/* then add irq resource */
> > +	for (i = 0; i < ddev->num_irqs; i++) {
> > +		res[i + 1].flags = IORESOURCE_IRQ;
> > +		res[i + 1].start = ddev->irqs[i];
> > +		res[i + 1].end = ddev->irqs[i];
> > +	}
> > +
> > +	uio_pdata.name = DRIVER_NAME;
> > +	uio_pdata.version = "0";
> > +
> > +	pdevinfo.res = res;
> > +	pdevinfo.num_res = ddev->num_irqs + 1;
> > +	pdevinfo.parent = &ddev->dev;
> > +	pdevinfo.id = PLATFORM_DEVID_AUTO;
> > +	pdevinfo.data = &uio_pdata;
> > +	pdevinfo.size_data = sizeof(uio_pdata);
> > +
> > +	uio_pdev = platform_device_register_full(&pdevinfo);
> > +	if (!IS_ERR(uio_pdev))
> > +		dev_set_drvdata(dev, uio_pdev);
> > +
> > +	kfree(res);
> > +
> > +	return PTR_ERR_OR_ZERO(uio_pdev);
> > +}
> > +
> > +static void dfl_uio_pdev_remove(struct dfl_device *ddev)
> > +{
> > +	struct platform_device *uio_pdev = dev_get_drvdata(&ddev->dev);
> > +
> > +	platform_device_unregister(uio_pdev);
> > +}
> > +
> > +static struct dfl_driver dfl_uio_pdev_driver = {
> > +	.drv	= {
> > +		.name       = DRIVER_NAME,
> > +	},
> > +	.match	= dfl_uio_pdev_match,
> > +	.probe	= dfl_uio_pdev_probe,
> > +	.remove	= dfl_uio_pdev_remove,
> > +};
> Could move this to the top and remove the forward decl.

I think it may be unnecessary. If we move it to the top, then we should
forward declare the 3 callbacks.

> > +module_dfl_driver(dfl_uio_pdev_driver);
> > +
> > +MODULE_DESCRIPTION("DFL driver for Userspace I/O platform devices");
> > +MODULE_AUTHOR("Intel Corporation");
> > +MODULE_LICENSE("GPL v2");
> > diff --git a/drivers/fpga/dfl.c b/drivers/fpga/dfl.c
> > index 511b20f..dd90111 100644
> > --- a/drivers/fpga/dfl.c
> > +++ b/drivers/fpga/dfl.c
> > @@ -256,12 +256,13 @@ dfl_match_one_device(const struct dfl_device_id *id, struct dfl_device *ddev)
> >  	return NULL;
> >  }
> >  
> > -static int dfl_bus_match(struct device *dev, struct device_driver *drv)
> > +int dfl_match_device(struct dfl_device *ddev, struct dfl_driver *ddrv)
> >  {
> > -	struct dfl_device *ddev = to_dfl_dev(dev);
> > -	struct dfl_driver *ddrv = to_dfl_drv(drv);
> >  	const struct dfl_device_id *id_entry;
> >  
> > +	if (ddrv->match)
> > +		return ddrv->match(ddev);
> > +
> >  	id_entry = ddrv->id_table;
> >  	if (id_entry) {
> >  		while (id_entry->feature_id) {
> > @@ -275,6 +276,15 @@ static int dfl_bus_match(struct device *dev, struct device_driver *drv)
> >  
> >  	return 0;
> >  }
> > +EXPORT_SYMBOL_GPL(dfl_match_device);
> > +
> > +static int dfl_bus_match(struct device *dev, struct device_driver *drv)
> > +{
> > +	struct dfl_device *ddev = to_dfl_dev(dev);
> > +	struct dfl_driver *ddrv = to_dfl_drv(drv);
> > +
> > +	return dfl_match_device(ddev, ddrv);
> > +}
> >  
> >  static int dfl_bus_probe(struct device *dev)
> >  {
> > @@ -328,7 +338,7 @@ static struct attribute *dfl_dev_attrs[] = {
> >  };
> >  ATTRIBUTE_GROUPS(dfl_dev);
> >  
> > -static struct bus_type dfl_bus_type = {
> > +struct bus_type dfl_bus_type = {
> >  	.name		= "dfl",
> >  	.match		= dfl_bus_match,
> >  	.probe		= dfl_bus_probe,
> > @@ -336,6 +346,7 @@ static struct bus_type dfl_bus_type = {
> >  	.uevent		= dfl_bus_uevent,
> >  	.dev_groups	= dfl_dev_groups,
> >  };
> > +EXPORT_SYMBOL_GPL(dfl_bus_type);
> >  
> >  static void release_dfl_dev(struct device *dev)
> >  {
> > @@ -469,7 +480,8 @@ 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 ||
> > +	    (!dfl_drv->id_table && !dfl_drv->match))
> >  		return -EINVAL;
> >  
> >  	dfl_drv->drv.owner = owner;
> > diff --git a/include/linux/dfl.h b/include/linux/dfl.h
> > index 6cc1098..7bd97ec 100644
> > --- a/include/linux/dfl.h
> > +++ b/include/linux/dfl.h
> > @@ -11,6 +11,8 @@
> >  #include <linux/device.h>
> >  #include <linux/mod_devicetable.h>
> >  
> > +extern struct bus_type dfl_bus_type;
> 
> Why is this needed ?
> 
> This is a public interface, likely should happen somewhere in drivers/fpga

The dfl-uio-pdev module is using this variable. Do you mean we should
move it to DFL internal header file, drivers/fpga/dfl.h ?

> 
> > +
> >  /**
> >   * enum dfl_id_type - define the DFL FIU types
> >   */
> > @@ -51,6 +53,8 @@ struct dfl_device {
> >   * @drv: driver model structure.
> >   * @id_table: pointer to table of device IDs the driver is interested in.
> >   *	      { } member terminated.
> > + * @match: returns a positive value if given device can be handled by the
> returns one

Will change it.

> > + *	   driver and zero otherwise. If NULL, matching is based on id_table.
> >   * @probe: mandatory callback for device binding.
> >   * @remove: callback for device unbinding.
> >   */
> > @@ -58,6 +62,7 @@ struct dfl_driver {
> >  	struct device_driver drv;
> >  	const struct dfl_device_id *id_table;
> >  
> > +	int (*match)(struct dfl_device *dfl_dev);
> >  	int (*probe)(struct dfl_device *dfl_dev);
> >  	void (*remove)(struct dfl_device *dfl_dev);
> >  };
> > @@ -65,6 +70,8 @@ struct dfl_driver {
> >  #define to_dfl_dev(d) container_of(d, struct dfl_device, dev)
> >  #define to_dfl_drv(d) container_of(d, struct dfl_driver, drv)
> >  
> > +int dfl_match_device(struct dfl_device *ddev, struct dfl_driver *ddrv);
> 
> Is it really necessary put this as a public interface ?

I may move it to drivers/fpga/dfl.h

Thanks,
Yilun

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