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Date:   Thu, 1 Mar 2018 14:17:50 +0800
From:   Wu Hao <hao.wu@intel.com>
To:     Alan Tull <atull@kernel.org>
Cc:     Moritz Fischer <mdf@kernel.org>, linux-fpga@vger.kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-api@vger.kernel.org, "Kang, Luwei" <luwei.kang@intel.com>,
        "Zhang, Yi Z" <yi.z.zhang@intel.com>
Subject: Re: [PATCH v4 13/24] fpga: region: add compat_id support
Message-ID: <20180301061750.GB8999@hao-dev>
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On Wed, Feb 28, 2018 at 04:55:15PM -0600, Alan Tull wrote:
> On Tue, Feb 13, 2018 at 3:24 AM, Wu Hao <hao.wu@intel.com> wrote:
> 
> Hi Hao,

Hi Alan,

Thanks for the review.

> 
> > This patch introduces a compat_id member and sysfs interface for each
> > fpga-region, e.g userspace applications could read the compat_id
> > from the sysfs interface for compatibility checking before PR.
> >
> > Signed-off-by: Wu Hao <hao.wu@intel.com>
> > ---
> >  Documentation/ABI/testing/sysfs-class-fpga-region |  5 +++++
> >  drivers/fpga/fpga-region.c                        | 19 +++++++++++++++++++
> >  include/linux/fpga/fpga-region.h                  | 13 +++++++++++++
> >  3 files changed, 37 insertions(+)
> >  create mode 100644 Documentation/ABI/testing/sysfs-class-fpga-region
> >
> > diff --git a/Documentation/ABI/testing/sysfs-class-fpga-region b/Documentation/ABI/testing/sysfs-class-fpga-region
> > new file mode 100644
> > index 0000000..419d930
> > --- /dev/null
> > +++ b/Documentation/ABI/testing/sysfs-class-fpga-region
> > @@ -0,0 +1,5 @@
> > +What:          /sys/class/fpga_region/<region>/compat_id
> > +Date:          February 2018
> > +KernelVersion: 4.16
> > +Contact:       Wu Hao <hao.wu@intel.com>
> > +Description:   FPGA region id for compatibility check.
> > diff --git a/drivers/fpga/fpga-region.c b/drivers/fpga/fpga-region.c
> > index 660a91b..babec96 100644
> > --- a/drivers/fpga/fpga-region.c
> > +++ b/drivers/fpga/fpga-region.c
> > @@ -162,6 +162,24 @@ int fpga_region_program_fpga(struct fpga_region *region)
> >  }
> >  EXPORT_SYMBOL_GPL(fpga_region_program_fpga);
> >
> > +static ssize_t compat_id_show(struct device *dev,
> > +                             struct device_attribute *attr, char *buf)
> > +{
> > +       struct fpga_region *region = to_fpga_region(dev);
> 
> This looks good, but not all users of FPGA are going to use compat_id.
> How would you feel about making it a pointer in struct fpga_region?
> With compat_id as a pointer, could check for non-null compat_id
> pointer and return an error if it wasn't initialized.

It sounds good to me.

if (!region->compat_id)
	return -ENOENT;

> 
> > +
> > +       return sprintf(buf, "%016llx%016llx\n",
> > +                      (unsigned long long)region->compat_id.id_h,
> > +                      (unsigned long long)region->compat_id.id_l);
> > +}
> > +
> > +static DEVICE_ATTR_RO(compat_id);
> > +
> > +static struct attribute *fpga_region_attrs[] = {
> > +       &dev_attr_compat_id.attr,
> > +       NULL,
> > +};
> > +ATTRIBUTE_GROUPS(fpga_region);
> > +
> >  int fpga_region_register(struct fpga_region *region)
> >  {
> >         struct device *dev = region->parent;
> > @@ -226,6 +244,7 @@ static int __init fpga_region_init(void)
> >         if (IS_ERR(fpga_region_class))
> >                 return PTR_ERR(fpga_region_class);
> >
> > +       fpga_region_class->dev_groups = fpga_region_groups;
> >         fpga_region_class->dev_release = fpga_region_dev_release;
> >
> >         return 0;
> > diff --git a/include/linux/fpga/fpga-region.h b/include/linux/fpga/fpga-region.h
> > index 423c87e..bf97dcc 100644
> > --- a/include/linux/fpga/fpga-region.h
> > +++ b/include/linux/fpga/fpga-region.h
> > @@ -6,6 +6,17 @@
> >  #include <linux/fpga/fpga-bridge.h>
> >
> >  /**
> > + * struct fpga_region_compat_id - FPGA Region id for compatibility check
> > + *
> > + * @id_h: high 64bit of the compat_id
> > + * @id_l: low 64bit of the compat_id
> > + */
> > +struct fpga_region_compat_id {
> > +       u64 id_h;
> > +       u64 id_l;
> 
> I guess each user will choose how to define these bits.

Yes.

> 
> > +};
> > +
> > +/**
> >   * struct fpga_region - FPGA Region structure
> >   * @dev: FPGA Region device
> >   * @parent: parent device
> > @@ -13,6 +24,7 @@
> >   * @bridge_list: list of FPGA bridges specified in region
> >   * @mgr: FPGA manager
> >   * @info: FPGA image info
> > + * @compat_id: FPGA region id for compatibility check.
> >   * @priv: private data
> >   * @get_bridges: optional function to get bridges to a list
> >   * @groups: optional attribute groups.
> > @@ -24,6 +36,7 @@ struct fpga_region {
> >         struct list_head bridge_list;
> >         struct fpga_manager *mgr;
> >         struct fpga_image_info *info;
> > +       struct fpga_region_compat_id compat_id;
> 
> Here it would be a pointer instead.

Yes. Will update this patch.

Thanks
Hao

> 
> Alan
> 
> >         void *priv;
> >         int (*get_bridges)(struct fpga_region *region);
> >         const struct attribute_group **groups;
> > --
> > 2.7.4
> >