linux-kernel - RE: [PATCH] staging: comedi: cast to (unsigned int *)

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Message-ID: <21a953261eb44e7ba302cfe74d8efa2d@AcuMS.aculab.com>
Date:   Fri, 19 Feb 2021 09:03:59 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Ian Abbott' <abbotti@....co.uk>,
        Greg KH <gregkh@...uxfoundation.org>,
        Atul Gopinathan <atulgopinathan@...il.com>
CC:     "devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] staging: comedi: cast to (unsigned int *)

> It's kind of moot anyway because the patch is outdated.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

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