linux-kernel - Re: [PATCH v6 00/28] NT synchronization primitive driver

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Message-ID: <6110961.lOV4Wx5bFT@camazotz>
Date: Mon, 09 Dec 2024 16:08:08 -0600
From: Elizabeth Figura <zfigura@...eweavers.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Jonathan Corbet <corbet@....net>, shuah <shuah@...nel.org>,
 Arnd Bergmann <arnd@...db.de>
Cc: linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
 wine-devel@...ehq.org,
 André Almeida <andrealmeid@...lia.com>,
 Wolfram Sang <wsa@...nel.org>, Arkadiusz Hiler <ahiler@...eweavers.com>,
 Peter Zijlstra <peterz@...radead.org>, Andy Lutomirski <luto@...nel.org>,
 linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
 Randy Dunlap <rdunlap@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>,
 Boqun Feng <boqun.feng@...il.com>
Subject: Re: [PATCH v6 00/28] NT synchronization primitive driver

On Monday, 9 December 2024 14:24:36 CST Arnd Bergmann wrote:
> On Mon, Dec 9, 2024, at 19:58, Elizabeth Figura wrote:
> > == Previous versions ==
> >
> > No changes were made from v5 other than rebasing on top of the 6.13-rc1
> > char-misc-next tree.
> >
> > I would like to repeat a question from the last round of review, though. Two
> > changes were suggested related to API design, which I did not make because the
> > APIs in question were already released in upstream Linux. However, the driver is
> > also completely nonfunctional and hidden behind BROKEN, so would this be
> > acceptable anyway? The changes in question are:
> 
> If it was impossible to use the driver, there is no regression.
> I feel the entire point of marking it as broken was to be able
> to add that type of change.

Makes sense. [I figured that the BROKEN was just there to prevent anyone from trying to use a half-finished driver, and the point of committing a half-finished driver was just to reduce the number of patches that needed to be resent.]

I'll make these changes and resend.

> > * rename NTSYNC_IOC_SEM_POST to NTSYNC_IOC_SEM_RELEASE (matching the NT
> >   terminology instead of POSIX),
> 
> No objections my me on either name.
> 
> > * change object creation ioctls to return the fds directly in the return value
> >   instead of through the args struct. I would also still appreciate a
> >   clarification on the advice in [1], which is why I didn't do this in the first
> >   place.
> >
> >   [1] https://docs.kernel.org/driver-api/ioctl.html#return-code
> 
> The git log tells me that I have written that, but I don't remember
> why I put that in, maybe someone else suggested it.
> 
> My feeling right now is that returning a file descriptor number
> as a small positive integer from the ioctl() return code makes
> sense. On the other hand, returning pointers, negative signed
> integers or large (> 32bit) 'unsigned long' values can cause
> a number of issues, so I would avoid all those the same way we
> discourage passing those integers as a literal 'arg' into ioctl()
> instead of going through a pointer.

Ah, that makes sense to me, thanks.