From: David Laight <David.Laight@ACULAB.COM>
To: 'Ian Abbott' <abbotti@mev.co.uk>,
Greg KH <gregkh@linuxfoundation.org>,
Atul Gopinathan <atulgopinathan@gmail.com>
Cc: "devel@driverdev.osuosl.org" <devel@driverdev.osuosl.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] staging: comedi: cast to (unsigned int *)
Date: Fri, 19 Feb 2021 09:03:59 +0000 [thread overview]
Message-ID: <21a953261eb44e7ba302cfe74d8efa2d@AcuMS.aculab.com> (raw)
In-Reply-To: <3cfef23d-8d4a-205c-61e8-cbe8c9a0c0f4@mev.co.uk>
> It's kind of moot anyway because the patch is outdated. But the reason
> for the ___force is that the same `struct comedi_cmd` is used in both
> user and kernel contexts. In user contexts, the `chanlist` member
> points to user memory and in kernel contexts it points to kernel memory
> (copied from userspace).
Can't you use a union of the user and kernel pointers?
(Possibly even anonymous?)
Although, ideally, keeping them in separate fields is better.
8 bytes for a pointer isn't going make a fat lot of difference.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
WARNING: multiple messages have this Message-ID (diff)
From: David Laight <David.Laight@ACULAB.COM>
To: 'Ian Abbott' <abbotti@mev.co.uk>,
Greg KH <gregkh@linuxfoundation.org>,
Atul Gopinathan <atulgopinathan@gmail.com>
Cc: "devel@driverdev.osuosl.org" <devel@driverdev.osuosl.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] staging: comedi: cast to (unsigned int *)
Date: Fri, 19 Feb 2021 09:03:59 +0000 [thread overview]
Message-ID: <21a953261eb44e7ba302cfe74d8efa2d@AcuMS.aculab.com> (raw)
In-Reply-To: <3cfef23d-8d4a-205c-61e8-cbe8c9a0c0f4@mev.co.uk>
> It's kind of moot anyway because the patch is outdated. But the reason
> for the ___force is that the same `struct comedi_cmd` is used in both
> user and kernel contexts. In user contexts, the `chanlist` member
> points to user memory and in kernel contexts it points to kernel memory
> (copied from userspace).
Can't you use a union of the user and kernel pointers?
(Possibly even anonymous?)
Although, ideally, keeping them in separate fields is better.
8 bytes for a pointer isn't going make a fat lot of difference.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
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next prev parent reply other threads:[~2021-02-19 9:09 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-17 16:59 [PATCH] staging: comedi: cast to (unsigned int *) Atul Gopinathan
2021-02-17 16:59 ` Atul Gopinathan
2021-02-17 17:35 ` Greg KH
2021-02-17 17:35 ` Greg KH
2021-02-17 18:10 ` Atul Gopinathan
2021-02-17 18:10 ` Atul Gopinathan
2021-02-17 18:26 ` Greg KH
2021-02-17 18:26 ` Greg KH
2021-02-18 11:04 ` Ian Abbott
2021-02-18 11:04 ` Ian Abbott
2021-02-19 9:03 ` David Laight [this message]
2021-02-19 9:03 ` David Laight
2021-02-19 9:26 ` Dan Carpenter
2021-02-19 9:26 ` Dan Carpenter
2021-02-19 9:36 ` David Laight
2021-02-19 9:36 ` David Laight
2021-02-19 9:31 ` Ian Abbott
2021-02-19 9:31 ` Ian Abbott
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