linux-kernel - Re: [RFC v2 1/1] fpga-region: Add generic IOCTL interface for runtime FPGA programming

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Message-Id: <7f818704-d40c-42da-b2c5-942d31e1d9dc@app.fastmail.com>
Date: Mon, 17 Mar 2025 22:12:46 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Nava kishore Manne" <nava.kishore.manne@....com>, git@....com,
 mdf@...nel.org, hao.wu@...el.com, yilun.xu@...el.com,
 "Tom Rix" <trix@...hat.com>, "Rob Herring" <robh@...nel.org>,
 "Saravana Kannan" <saravanak@...gle.com>, linux-kernel@...r.kernel.org,
 linux-fpga@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [RFC v2 1/1] fpga-region: Add generic IOCTL interface for runtime FPGA
 programming

> + * FPGA Region Control IOCTLs.
> + */
> +#define FPGA_REGION_MAGIC	'f'
> +#define FPGA_IOW(num, dtype)	_IOW(FPGA_REGION_MAGIC, num, dtype)
> +#define FPGA_IOR(num, dtype)	_IOR(FPGA_REGION_MAGIC, num, dtype)
> +
> +#define FPGA_REGION_IOCTL_LOAD		FPGA_IOW(0, __u32)
> +#define FPGA_REGION_IOCTL_REMOVE        FPGA_IOW(1, __u32)
> +#define FPGA_REGION_IOCTL_STATUS        FPGA_IOR(2, __u32)

The definition does not appear to match the usage in the driver,
since you don't pass a __u32 structure but instead a 
fpga_region_config_info.

Please also remove the extra FPGA_IOW/FPGA_IOR macros and just use
_IOW/IOR directly so it is possible to process the headers when
identifying ioctl command codes.

The 'f' range seems to be rather overloaded already with filesystem
ioctls:

'f'   00-1F  linux/ext2_fs.h                                         conflict!
'f'   00-1F  linux/ext3_fs.h                                         conflict!
'f'   00-0F  fs/jfs/jfs_dinode.h                                     conflict!
'f'   00-0F  fs/ext4/ext4.h                                          conflict!
'f'   00-0F  linux/fs.h                                              conflict!
'f'   00-0F  fs/ocfs2/ocfs2_fs.h                                     conflict!

In particular, the numbers you have defined are very similar to these:
some of these:

#define FS_IOC_GETFLAGS                 _IOR('f', 1, long)
#define FS_IOC_SETFLAGS                 _IOW('f', 2, long)

      Arnd