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    SubjectRe: [PATCH v4 13/24] fpga: region: add compat_id support
    On Tue, Feb 13, 2018 at 3:24 AM, Wu Hao <hao.wu@intel.com> wrote:

    Hi Hao,

    > 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.

    > +
    > + 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.

    > +};
    > +
    > +/**
    > * 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.

    Alan

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

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