linux-kernel - Re: [RFC v2 10/16] luo: luo

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Message-ID: <20250714143443.GF1870174@ziepe.ca>
Date: Mon, 14 Jul 2025 11:34:43 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Mike Rapoport <rppt@...nel.org>
Cc: Pratyush Yadav <pratyush@...nel.org>,
	Christian Brauner <brauner@...nel.org>,
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Subject: Re: [RFC v2 10/16] luo: luo_ioctl: add ioctl interface

On Thu, Jul 10, 2025 at 10:26:45AM +0300, Mike Rapoport wrote:
> IIUC Christian's point was mostly not about using VFS APIs (i.e.
> read/write) but about using a special pseudo fs rather than devtmpfs to
> drive ioctls.
>  
> So instead of 
> 
> 	fd = open("/dev/liveupdate", ...);
> 	ioctl(fd, ...);
> 
> we'd use
> 
> 	fd = open("/sys/fs/kexec/control", ...);
> 	ioctl(fd, ...);

Please no, /sys/ is much worse.

/dev/ has lots of infrastructure to control permissions/etc that /sys/
does not.

If you want to do ioctls to something that you open() is a character
dev and you accept the limitations with namespaces, coarse permissions
and so on.

Jason