From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mslow1.mail.gandi.net (mslow1.mail.gandi.net [217.70.178.240]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8505372 for ; Tue, 4 May 2021 15:59:26 +0000 (UTC) Received: from relay5-d.mail.gandi.net (unknown [217.70.183.197]) by mslow1.mail.gandi.net (Postfix) with ESMTP id 9734ED41DA for ; Tue, 4 May 2021 15:34:08 +0000 (UTC) X-Originating-IP: 90.65.108.55 Received: from localhost (lfbn-lyo-1-1676-55.w90-65.abo.wanadoo.fr [90.65.108.55]) (Authenticated sender: alexandre.belloni@bootlin.com) by relay5-d.mail.gandi.net (Postfix) with ESMTPSA id 2AB0A1C0007; Tue, 4 May 2021 15:33:59 +0000 (UTC) Date: Tue, 4 May 2021 17:33:59 +0200 From: Alexandre Belloni To: Maxime Ripard Cc: Samuel Holland , Alessandro Zummo , Chen-Yu Tsai , Jernej Skrabec , linux-rtc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] rtc: sun6i: Add NVMEM provider Message-ID: References: <20210419014549.26900-1-samuel@sholland.org> <20210430090206.lybmygrt636nysoc@gilmour> X-Mailing-List: linux-sunxi@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210430090206.lybmygrt636nysoc@gilmour> On 30/04/2021 11:02:06+0200, Maxime Ripard wrote: > Hi, > > On Sun, Apr 18, 2021 at 08:45:49PM -0500, Samuel Holland wrote: > > The sun6i RTC provides 32 bytes of general-purpose data registers. > > They can be used to save data in the always-on RTC power domain. > > The registers are writable via 32-bit MMIO accesses only. > > > > Expose the region as a NVMEM provider so it can be used by userspace and > > other drivers. > > > > Signed-off-by: Samuel Holland > > As far as I understood, you want to use those registers to implement > super-standby? If so, while it makes sense for the kernel to be able to > be able to write to those registers, I guess it would be a bit unwise to > allow the userspace to access it? I would think nvmem is still the proper subsystem. I guess maybe we should have a version of __nvmem_device_get that would ensure exclusive access to a cell, thus preventing userspace accessing it as long a the kernel is using it. -- Alexandre Belloni, co-owner and COO, Bootlin Embedded Linux and Kernel engineering https://bootlin.com