From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-wm1-x342.google.com ([2a00:1450:4864:20::342]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1gpIm2-0002vG-FJ for barebox@lists.infradead.org; Thu, 31 Jan 2019 20:17:23 +0000 Received: by mail-wm1-x342.google.com with SMTP id b11so3861101wmj.1 for ; Thu, 31 Jan 2019 12:17:21 -0800 (PST) MIME-Version: 1.0 References: <20190129065549.29161-1-andrew.smirnov@gmail.com> <20190129065549.29161-19-andrew.smirnov@gmail.com> <20190129084847.spkfbeksb7xne46g@pengutronix.de> <20190131105452.smetw36klsxmvtaq@localhost.localdomain> In-Reply-To: <20190131105452.smetw36klsxmvtaq@localhost.localdomain> From: Andrey Smirnov Date: Thu, 31 Jan 2019 12:17:08 -0800 Message-ID: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: Re: [PATCH v2 18/19] drivers: mem: Create file to access second half of 64-bit memory To: Peter Mamonov Cc: Barebox List On Thu, Jan 31, 2019 at 2:55 AM Peter Mamonov wrote: > > Hello, Andrey, > > > In order to allow access to second half of address space on 64-bit > > machines, add code that creates /dev/highmem dedicated for that. > > > > Note that due to maximum file size being limited to MAX_LFS_FILESIZE > > or 0x7fff_ffff_ffff_ffff bytes at addresses 0x7fff_ffff_ffff_ffff and > > 0xffff_ffff_ffff_ffff cannot be access through /dev/mem and > > /dev/hightmem correspondingly. > > Does it imply using `-s /dev/highmem` argument when accessing addresses beyond > MAX_LFS_FILESIZE? Yes, it does. > That's not very convenient: > > $ git grep -l /dev/mem > commands/crc.c > commands/digest.c > commands/disasm.c > commands/md.c > commands/memcmp.c > commands/memcpy.c > commands/memset.c > commands/mm.c > commands/mw.c > I don't disagree, but there isn't much that can be done about that AFAICT. The first version of this fix kept single /dev/mem file, but ended up introducing quite a bit of special cases all over the FS layer, so it was rejected. The only two options to make it more convenient that I can see would be to either modify "/dev/mem" users to make "/dev/highmem" substitution automatically based on offset they are given, or, assuming it is possible, create a mapping that would expose all of the interesting registers on MIPS64 in the lower half of 64-bit address space. Thanks, Andrey Smirnov _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox