Re: [PATCH rust-next v2 0/3] rust: miscdevice: add llseek support

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Oct 16, 2025 at 07:19:51PM +0900, Ryosuke Yasuoka wrote:
> On Wed, Oct 15, 2025 at 07:40:12AM +0200, Greg KH wrote:
> > On Wed, Oct 15, 2025 at 01:02:40PM +0900, Ryosuke Yasuoka wrote:
> > > Hi all,
> > > 
> > > This patch series add support for the llseek file operation to misc
> > > devices written in Rust.
> > 
> > Cool, but what miscdevice driver needs llseek support?  Do you have a
> > real user for this that we can see as well?
> 
> Currently no. Because lseek is one of fundamental functions for device
> driver, I think it's valuable to add support. I believe we'll have real
> users based on read, write, and this lseek support.

Char devices that use lseek are "odd", don't you agree?  There are no
such current users under drivers/misc/ and only a rare few under
drivers/char/ (the huge user of that is mem.c but we aren't going to be
reimplementing that in rust any time soon...)

So without a real user of this api, I suggest we hold-off on adding it.
Let's not add it until someone comes up with a very valid reason for it.

thanks,

greg k-h