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Message-ID: <53097eaf-02ee-8e41-9738-107115dc9dcd@redhat.com>
Date: Mon, 7 Dec 2020 05:07:05 -0800
From: Tom Rix <trix@...hat.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: yilun.xu@...el.com, hao.wu@...el.com, mdf@...nel.org,
linux-kernel@...r.kernel.org, linux-fpga@...r.kernel.org
Subject: Re: [RFC] fpga: dfl: a prototype uio driver
On 12/7/20 12:02 AM, Greg KH wrote:
> On Sun, Dec 06, 2020 at 01:55:54PM -0800, trix@...hat.com wrote:
>> From: Tom Rix <trix@...hat.com>
>>
>> >From [PATCH 0/2] UIO support for dfl devices
>> https://lore.kernel.org/linux-fpga/1602828151-24784-1-git-send-email-yilun.xu@intel.com/
> Why is this here?
As reference, Yilun's work has precedence for a uio driver and this rfc is trying to address what i believe is a sticking point of the driver override. This rfc is some code i hacked out to show the idea and move uio support along. I would like to see uio support for at least the unclaimed feature id's because this would make it easier for them to be developed.
>> Here is an idea to have uio support with no driver override.
>>
>> This makes UIO the primary driver interface because every feature
>> will have one and makes the existing platform driver interface
>> secondary. There will be a new burden for locking write access when
>> they compete.
>>
>> Example shows finding the fpga's temperture.
>>
>> Signed-off-by: Tom Rix <trix@...hat.com>
>> ---
>> drivers/fpga/dfl-fme-main.c | 9 +++-
>> drivers/fpga/dfl-uio.c | 96 +++++++++++++++++++++++++++++++++++++
>> drivers/fpga/dfl.c | 44 ++++++++++++++++-
>> drivers/fpga/dfl.h | 9 ++++
>> uio.c | 56 ++++++++++++++++++++++
>> 5 files changed, 212 insertions(+), 2 deletions(-)
>> create mode 100644 drivers/fpga/dfl-uio.c
>> create mode 100644 uio.c
>>
>> diff --git a/drivers/fpga/dfl-fme-main.c b/drivers/fpga/dfl-fme-main.c
>> index 037dc4f946f0..3323e90a18c4 100644
>> --- a/drivers/fpga/dfl-fme-main.c
>> +++ b/drivers/fpga/dfl-fme-main.c
>> @@ -709,12 +709,18 @@ static int fme_probe(struct platform_device *pdev)
>> if (ret)
>> goto dev_destroy;
>>
>> - ret = dfl_fpga_dev_ops_register(pdev, &fme_fops, THIS_MODULE);
>> + ret = dfl_fpga_dev_feature_init_uio(pdev, DFH_TYPE_FIU);
>> if (ret)
>> goto feature_uinit;
>>
>> + ret = dfl_fpga_dev_ops_register(pdev, &fme_fops, THIS_MODULE);
>> + if (ret)
>> + goto feature_uinit_uio;
>> +
>> return 0;
>>
>> +feature_uinit_uio:
>> + dfl_fpga_dev_feature_uinit_uio(pdev, DFH_TYPE_FIU);
>> feature_uinit:
>> dfl_fpga_dev_feature_uinit(pdev);
>> dev_destroy:
>> @@ -726,6 +732,7 @@ exit:
>> static int fme_remove(struct platform_device *pdev)
>> {
>> dfl_fpga_dev_ops_unregister(pdev);
>> + dfl_fpga_dev_feature_uinit_uio(pdev, DFH_TYPE_FIU);
>> dfl_fpga_dev_feature_uinit(pdev);
>> fme_dev_destroy(pdev);
>>
>> diff --git a/drivers/fpga/dfl-uio.c b/drivers/fpga/dfl-uio.c
>> new file mode 100644
>> index 000000000000..7610ee0b19dc
>> --- /dev/null
>> +++ b/drivers/fpga/dfl-uio.c
>> @@ -0,0 +1,96 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + * prototype dfl uio driver
>> + *
>> + * Copyright Tom Rix 2020
>> + */
>> +#include <linux/module.h>
>> +#include "dfl.h"
>> +
>> +static irqreturn_t dfl_uio_handler(int irq, struct uio_info *info)
>> +{
>> + return IRQ_HANDLED;
>> +}
>> +
>> +static int dfl_uio_mmap(struct uio_info *info, struct vm_area_struct *vma)
>> +{
>> + int ret = -ENODEV;
>> + return ret;
> Did you run this through checkpatch?
>
> Does the code make sense?
>
>> +}
>> +
>> +static int dfl_uio_open(struct uio_info *info, struct inode *inode)
>> +{
>> + int ret = -ENODEV;
>> + struct dfl_feature *feature = container_of(info, struct dfl_feature, uio);
>> + if (feature->dev)
>> + mutex_lock(&feature->lock);
>> +
>> + ret = 0;
>> + return ret;
> Same here, does this make sense?
>
> And wait, you are having userspace grab a kernel lock? What could go
> wrong? :(
>
Yes, this is the bad part of this idea.
Tom
>> +}
>> +
>> +static int dfl_uio_release(struct uio_info *info, struct inode *inode)
>> +{
>> + int ret = -ENODEV;
>> + struct dfl_feature *feature = container_of(info, struct dfl_feature, uio);
>> + if (feature->dev)
>> + mutex_unlock(&feature->lock);
>> +
>> + ret = 0;
>> + return ret;
>> +}
>> +
>> +static int dfl_uio_irqcontrol(struct uio_info *info, s32 irq_on)
>> +{
>> + int ret = -ENODEV;
>> + return ret;
>> +}
>> +
>> +int dfl_uio_add(struct dfl_feature *feature)
>> +{
>> + struct uio_info *uio = &feature->uio;
>> + struct resource *res =
>> + &feature->dev->resource[feature->resource_index];
>> + int ret = 0;
>> +
>> + uio->name = kasprintf(GFP_KERNEL, "dfl-uio-%llx", feature->id);
>> + if (!uio->name) {
>> + ret = -ENOMEM;
>> + goto exit;
>> + }
>> +
>> + uio->version = "0.1";
>> + uio->mem[0].memtype = UIO_MEM_PHYS;
>> + uio->mem[0].addr = res->start & PAGE_MASK;
>> + uio->mem[0].offs = res->start & ~PAGE_MASK;
>> + uio->mem[0].size = (uio->mem[0].offs + resource_size(res)
>> + + PAGE_SIZE - 1) & PAGE_MASK;
>> + /* How are nr_irqs > 1 handled ??? */
>> + if (feature->nr_irqs == 1)
>> + uio->irq = feature->irq_ctx[0].irq;
>> + uio->handler = dfl_uio_handler;
>> + //uio->mmap = dfl_uio_mmap;
> ???
>
> I don't understand what this patch is trying to show...
> thanks,
>
> greg k-h
>
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