linux-kernel - Re: [PATCH v4 13/24] fpga: region: add compat

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Message-ID: <20180306005658.GA32057@hao-dev>
Date:   Tue, 6 Mar 2018 08:56:58 +0800
From:   Wu Hao <hao.wu@...el.com>
To:     Alan Tull <atull@...nel.org>
Cc:     Moritz Fischer <mdf@...nel.org>, linux-fpga@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api@...r.kernel.org, "Kang, Luwei" <luwei.kang@...el.com>,
        "Zhang, Yi Z" <yi.z.zhang@...el.com>
Subject: Re: [PATCH v4 13/24] fpga: region: add compat_id support

On Mon, Mar 05, 2018 at 01:42:41PM -0600, Alan Tull wrote:
> On Thu, Mar 1, 2018 at 12:17 AM, Wu Hao <hao.wu@...el.com> wrote:
> > 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@...el.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@...el.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@...el.com>
> >> > +Description:   FPGA region id for compatibility check.
> 
> It would be helpful to add some explanation here that although the
> intended function of compat_id is set, the way the actual value is
> defined or calculated is set by the layer that is creating the FPGA
> region.

Sure.

Description: FPGA region id for compatibility check, e.g compatibility
             of the FPGA reconfiguration hardware and image. This value
             is defined or calculated by the layer that is creating the
             FPGA region. This interface returns the compat_id value or
             just error code -ENOENT in case compat_id is not used.

> 
> >> > 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;
> 
> Yes, thanks!

Thanks for the review.

Hao

> 
> Alan
> 
> >
> >>
> >> > +
> >> > +       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
> >> >
> > --
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