Re: [RFC PATCH 07/20] famfs: Add include/linux/famfs_ioctl.h

From: Randy Dunlap <rdunlap@infradead.org>
To: John Groves <John@groves.net>
Cc: John Groves <jgroves@micron.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Dan Williams <dan.j.williams@intel.com>,
	Vishal Verma <vishal.l.verma@intel.com>,
	Dave Jiang <dave.jiang@intel.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
	Matthew Wilcox <willy@infradead.org>,
	linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	nvdimm@lists.linux.dev, john@jagalactic.com,
	Dave Chinner <david@fromorbit.com>,
	Christoph Hellwig <hch@infradead.org>,
	dave.hansen@linux.intel.com, gregory.price@memverge.com
Subject: Re: [RFC PATCH 07/20] famfs: Add include/linux/famfs_ioctl.h
Date: Fri, 23 Feb 2024 19:27:22 -0800	[thread overview]
Message-ID: <97cde8f6-21ed-45b9-9618-568933102f05@infradead.org> (raw)
In-Reply-To: <7onhdq4spd7mnkr5c443sbvnr7l4n34amtterg4soiey2qubyl@r2ppa6fsohnk>

Hi John,

On 2/23/24 18:23, John Groves wrote:
>>> +
>>> +#define FAMFSIOC_MAGIC 'u'
>> This 'u' value should be documented in
>> Documentation/userspace-api/ioctl/ioctl-number.rst.
>>
>> and if possible, you might want to use values like 0x5x or 0x8x
>> that don't conflict with the ioctl numbers that are already used
>> in the 'u' space.
> Will do. I was trying to be too clever there, invoking "mu" for
> micron. 

I might have been unclear about this one.
It's OK to use 'u' but the values 1-4 below conflict in the 'u' space:

'u'   00-1F  linux/smb_fs.h                                          gone
'u'   20-3F  linux/uvcvideo.h                                        USB video class host driver
'u'   40-4f  linux/udmabuf.h

so if you could use
'u'   50-5f
or
'u'   80-8f

then those conflicts wouldn't be there.
HTH.

>>> +
>>> +/* famfs file ioctl opcodes */
>>> +#define FAMFSIOC_MAP_CREATE    _IOW(FAMFSIOC_MAGIC, 1, struct famfs_ioc_map)
>>> +#define FAMFSIOC_MAP_GET       _IOR(FAMFSIOC_MAGIC, 2, struct famfs_ioc_map)
>>> +#define FAMFSIOC_MAP_GETEXT    _IOR(FAMFSIOC_MAGIC, 3, struct famfs_extent)
>>> +#define FAMFSIOC_NOP           _IO(FAMFSIOC_MAGIC,  4)

-- 
#Randy