linux-kernel - Re: [RESEND PATCH v11 1/2] uio: uio_dfl: add userspace i/o driver for DFL bus

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Date:   Sat, 27 Feb 2021 16:42:55 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Xu Yilun <yilun.xu@...el.com>
Cc:     mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, trix@...hat.com, lgoncalv@...hat.com,
        hao.wu@...el.com
Subject: Re: [RESEND PATCH v11 1/2] uio: uio_dfl: add userspace i/o driver
 for DFL bus

On Sat, Feb 27, 2021 at 11:27:03PM +0800, 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 now only binds the ether group feature, which has no irq. So
> the irq support is not implemented yet.
> 
> Signed-off-by: Xu Yilun <yilun.xu@...el.com>
> Reviewed-by: Tom Rix <trix@...hat.com>
> ---
> v9: switch to add a uio driver in drivers/uio
> v10: add the source file in MAINTAINERS
>      more descriptive Kconfig header
>      add detailed path for opae uio example
> v11: no change
> ---
>  MAINTAINERS           |  1 +
>  drivers/uio/Kconfig   | 17 +++++++++++++
>  drivers/uio/Makefile  |  1 +
>  drivers/uio/uio_dfl.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 85 insertions(+)
>  create mode 100644 drivers/uio/uio_dfl.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 000fe0b..4dc0354 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -6943,6 +6943,7 @@ S:	Maintained
>  F:	Documentation/ABI/testing/sysfs-bus-dfl*
>  F:	Documentation/fpga/dfl.rst
>  F:	drivers/fpga/dfl*
> +F:	drivers/uio/uio_dfl.c
>  F:	include/linux/dfl.h
>  F:	include/uapi/linux/fpga-dfl.h
>  
> diff --git a/drivers/uio/Kconfig b/drivers/uio/Kconfig
> index 202ee81..5531f3a 100644
> --- a/drivers/uio/Kconfig
> +++ b/drivers/uio/Kconfig
> @@ -165,4 +165,21 @@ config UIO_HV_GENERIC
>  	  to network and storage devices from userspace.
>  
>  	  If you compile this as a module, it will be called uio_hv_generic.
> +
> +config UIO_DFL
> +	tristate "Generic driver for DFL (Device Feature List) bus"
> +	depends on FPGA_DFL
> +	help
> +	  Generic DFL (Device Feature List) driver for Userspace I/O devices.
> +	  It is useful to provide direct access to DFL devices from userspace.
> +	  A sample userspace application using this driver is available for
> +	  download in a git repository:
> +
> +	    git clone https://github.com/OPAE/opae-sdk.git
> +
> +	  It could be found at:
> +
> +	    opae-sdk/tools/libopaeuio/
> +
> +	  If you compile this as a module, it will be called uio_dfl.
>  endif
> diff --git a/drivers/uio/Makefile b/drivers/uio/Makefile
> index c285dd2..f2f416a1 100644
> --- a/drivers/uio/Makefile
> +++ b/drivers/uio/Makefile
> @@ -11,3 +11,4 @@ obj-$(CONFIG_UIO_PRUSS)         += uio_pruss.o
>  obj-$(CONFIG_UIO_MF624)         += uio_mf624.o
>  obj-$(CONFIG_UIO_FSL_ELBC_GPCM)	+= uio_fsl_elbc_gpcm.o
>  obj-$(CONFIG_UIO_HV_GENERIC)	+= uio_hv_generic.o
> +obj-$(CONFIG_UIO_DFL)	+= uio_dfl.o
> diff --git a/drivers/uio/uio_dfl.c b/drivers/uio/uio_dfl.c
> new file mode 100644
> index 0000000..89c0fc7
> --- /dev/null
> +++ b/drivers/uio/uio_dfl.c
> @@ -0,0 +1,66 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Generic DFL driver for Userspace I/O devicess
> + *
> + * Copyright (C) 2021 Intel Corporation, Inc.
> + */
> +#include <linux/dfl.h>
> +#include <linux/errno.h>
> +#include <linux/module.h>
> +#include <linux/uio_driver.h>
> +
> +#define DRIVER_NAME "uio_dfl"
> +
> +static int uio_dfl_probe(struct dfl_device *ddev)
> +{
> +	struct resource *r = &ddev->mmio_res;
> +	struct device *dev = &ddev->dev;
> +	struct uio_info *uioinfo;
> +	struct uio_mem *uiomem;
> +	int ret;
> +
> +	uioinfo = devm_kzalloc(dev, sizeof(struct uio_info), GFP_KERNEL);
> +	if (!uioinfo)
> +		return -ENOMEM;
> +
> +	uioinfo->name = DRIVER_NAME;
> +	uioinfo->version = "0";
> +
> +	uiomem = &uioinfo->mem[0];
> +	uiomem->memtype = UIO_MEM_PHYS;
> +	uiomem->addr = r->start & PAGE_MASK;
> +	uiomem->offs = r->start & ~PAGE_MASK;
> +	uiomem->size = (uiomem->offs + resource_size(r)
> +			+ PAGE_SIZE - 1) & PAGE_MASK;
> +	uiomem->name = r->name;
> +
> +	/* Irq is yet to be supported */
> +	uioinfo->irq = UIO_IRQ_NONE;
> +
> +	ret = devm_uio_register_device(dev, uioinfo);
> +	if (ret)
> +		dev_err(dev, "unable to register uio device\n");
> +
> +	return ret;
> +}
> +
> +#define FME_FEATURE_ID_ETH_GROUP	0x10

Why are you saying that an ethernet driver should be using the UIO
interface?

And why can't you use the existing UIO drivers that bind to memory
regions specified by firmware?  Without an interrupt being used, why is
UIO needed at all?

thanks,

greg k-h