From mboxrd@z Thu Jan 1 00:00:00 1970 From: alexandre.belloni@free-electrons.com (Alexandre Belloni) Date: Sun, 31 Jan 2016 12:34:09 +0100 Subject: [PATCH] misc: atmel-secumod: Driver for Atmel "security module". In-Reply-To: References: <1453348655-31182-1-git-send-email-davidm@egauge.net> <20160125110921.GA4027@piout.net> Message-ID: <20160131113409.GI20165@piout.net> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 29/01/2016 at 11:13:05 +1100, Finn Thain wrote : > > On Mon, 25 Jan 2016, David Mosberger wrote: > > > On Mon, Jan 25, 2016 at 4:09 AM, Alexandre Belloni > > wrote: > > > > > I know this does more than that but I think those thre sections should > > > be registered using the nvmem framework. The sysfs file creation and > > > accesses then comes for free. > > > > I think Finn's patches would have to go in for that first, since the > > existing nvram code is a mess. Even with Finn's patches in, I think it > > could go either way. > > I think Alexandre is speaking of the nvmem subsystem (not nvram). > Documentation/devicetree/bindings/nvmem > Documentation/nvmem > drivers/nvmem > absolutely. > > I'm not exactly sure how some of the features of the security module > > would be used: key management, auto erasing, there is a strange "backup > > mode" vs "normal mode" which is not well documented, etc. So I think it > > may well end up being sufficiently different to warrant a separate > > driver. > > nvmem is not a subsystem I am familiar with, so it's not immediately clear > to me what your driver would look like if re-written that way. > > Maybe it would become simpler. But if you did end up needing a separate > misc driver as well, maybe use of the nvmem framework would actually > increase complexity. > > It would depend on your requirements. But I would focus on the actual > requirement rather than uncertain future possibilities. > > > > > > Another idea is also to expose it using a genpool so it can be > > > accessed as sram from inside the kernel. > > > > That may be a fine idea, but as far as our application is concerned, we > > need user-level access to the battery-backed RAM. > > Right. I don't see how adding a memory allocator would help either. > While the immediate need is to use that sram from userspace, I think this is valuable to already think that at some point we will need to be able to partition and access that sram from the kernel. -- Alexandre Belloni, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com