Message-ID: <6f30a4c6-61a0-bb57-9f13-bcad3f3589b8@intel.com>
Date:   Mon, 26 Jul 2021 15:12:40 -0700
From:   Russ Weight <russell.h.weight@...el.com>
To:     <trix@...hat.com>, <hao.wu@...el.com>, <mdf@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <linux-fpga@...r.kernel.org>
Subject: Re: [PATCH] fpga: region: handle compat_id as an uuid

On 7/26/21 1:26 PM, trix@...hat.com wrote:
> From: Tom Rix <trix@...hat.com>
>
> An fpga region's compat_id is exported by the sysfs
> as a 128 bit hex string formed by concatenating two
> 64 bit values together.
>
> The only user of compat_id is dfl.  Its user library
> opae converts this value into a uuid.
>
> ex/
> $ cat /sys/class/fpga_region/region1/compat_id
> f3c9941350814aadbced07eb84a6d0bb
>
> Is reported as
> $ fpgainfo bmc
> ...
> Pr Interface Id                  : f3c99413-5081-4aad-bced-07eb84a6d0bb
>
> Storing a uuid as 2 64 bit values is vendor specific.
> And concatenating them together is vendor specific.
>
> It is better to store and print out as a vendor neutral uuid.
>
> Change fpga_compat_id from a struct to a union.
> Keep the old 64 bit values for dfl.
> Sysfs output is now
> f3c99413-5081-4aad-bced-07eb84a6d0bb

I'm fowarding feedback from Tim Whisonant, one of the OPAE userspace
developers:

I think that this change to the sysfs for the compat_id node will
end up breaking the SDK, which does not expect the '-' characters to
be included when parsing the sysfs value. Currently, it is parsed as
a raw hex string without regard to any '-' characters. This goes for
any "guid" currently exported by sysfs and for what we read in the
device MMIO space.

- Russ

>
> Signed-off-by: Tom Rix <trix@...hat.com>
> ---
>  .../ABI/testing/sysfs-class-fpga-region        |  4 ++--
>  drivers/fpga/dfl-fme-mgr.c                     |  8 ++++----
>  drivers/fpga/fpga-region.c                     |  4 +---
>  include/linux/fpga/fpga-mgr.h                  | 18 ++++++++++++------
>  include/linux/fpga/fpga-region.h               |  2 +-
>  5 files changed, 20 insertions(+), 16 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-class-fpga-region b/Documentation/ABI/testing/sysfs-class-fpga-region
> index bc7ec644acc9a..241359fb74a55 100644
> --- a/Documentation/ABI/testing/sysfs-class-fpga-region
> +++ b/Documentation/ABI/testing/sysfs-class-fpga-region
> @@ -5,5 +5,5 @@ Contact:	Wu Hao <hao.wu@...el.com>
>  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.
> +		FPGA region. This interface returns a uuid value or just
> +		error code -ENOENT in case compat_id is not used.
> diff --git a/drivers/fpga/dfl-fme-mgr.c b/drivers/fpga/dfl-fme-mgr.c
> index d5861d13b3069..012b72712684c 100644
> --- a/drivers/fpga/dfl-fme-mgr.c
> +++ b/drivers/fpga/dfl-fme-mgr.c
> @@ -273,16 +273,16 @@ static const struct fpga_manager_ops fme_mgr_ops = {
>  };
>  
>  static void fme_mgr_get_compat_id(void __iomem *fme_pr,
> -				  struct fpga_compat_id *id)
> +				  union fpga_compat_id *id)
>  {
> -	id->id_l = readq(fme_pr + FME_PR_INTFC_ID_L);
> -	id->id_h = readq(fme_pr + FME_PR_INTFC_ID_H);
> +	id->id_l = cpu_to_be64(readq(fme_pr + FME_PR_INTFC_ID_L));
> +	id->id_h = cpu_to_be64(readq(fme_pr + FME_PR_INTFC_ID_H));
>  }
>  
>  static int fme_mgr_probe(struct platform_device *pdev)
>  {
>  	struct dfl_fme_mgr_pdata *pdata = dev_get_platdata(&pdev->dev);
> -	struct fpga_compat_id *compat_id;
> +	union fpga_compat_id *compat_id;
>  	struct device *dev = &pdev->dev;
>  	struct fme_mgr_priv *priv;
>  	struct fpga_manager *mgr;
> diff --git a/drivers/fpga/fpga-region.c b/drivers/fpga/fpga-region.c
> index a4838715221ff..f1083b5894635 100644
> --- a/drivers/fpga/fpga-region.c
> +++ b/drivers/fpga/fpga-region.c
> @@ -166,9 +166,7 @@ static ssize_t compat_id_show(struct device *dev,
>  	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);
> +	return sprintf(buf, "%pU\n", &region->compat_id->uuid);
>  }
>  
>  static DEVICE_ATTR_RO(compat_id);
> diff --git a/include/linux/fpga/fpga-mgr.h b/include/linux/fpga/fpga-mgr.h
> index ec2cd8bfceb00..b12f9994932e1 100644
> --- a/include/linux/fpga/fpga-mgr.h
> +++ b/include/linux/fpga/fpga-mgr.h
> @@ -10,6 +10,7 @@
>  
>  #include <linux/mutex.h>
>  #include <linux/platform_device.h>
> +#include <linux/uuid.h>
>  
>  struct fpga_manager;
>  struct sg_table;
> @@ -144,14 +145,19 @@ struct fpga_manager_ops {
>  #define FPGA_MGR_STATUS_FIFO_OVERFLOW_ERR	BIT(4)
>  
>  /**
> - * struct fpga_compat_id - id for compatibility check
> - *
> + * union fpga_compat_id - id for compatibility check
> + * Can be accessed as either:
> + * @uuid: the base uuid_t type
> + * or
>   * @id_h: high 64bit of the compat_id
>   * @id_l: low 64bit of the compat_id
>   */
> -struct fpga_compat_id {
> -	u64 id_h;
> -	u64 id_l;
> +union fpga_compat_id {
> +	uuid_t uuid;
> +	struct {
> +		u64 id_h;
> +		u64 id_l;
> +	};
>  };
>  
>  /**
> @@ -169,7 +175,7 @@ struct fpga_manager {
>  	struct device dev;
>  	struct mutex ref_mutex;
>  	enum fpga_mgr_states state;
> -	struct fpga_compat_id *compat_id;
> +	union fpga_compat_id *compat_id;
>  	const struct fpga_manager_ops *mops;
>  	void *priv;
>  };
> diff --git a/include/linux/fpga/fpga-region.h b/include/linux/fpga/fpga-region.h
> index 27cb706275dba..7cc2ee543efb4 100644
> --- a/include/linux/fpga/fpga-region.h
> +++ b/include/linux/fpga/fpga-region.h
> @@ -24,7 +24,7 @@ struct fpga_region {
>  	struct list_head bridge_list;
>  	struct fpga_manager *mgr;
>  	struct fpga_image_info *info;
> -	struct fpga_compat_id *compat_id;
> +	union fpga_compat_id *compat_id;
>  	void *priv;
>  	int (*get_bridges)(struct fpga_region *region);
>  };

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