From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [63.81.120.155] (helo=imap.sh.mvista.com) by bombadil.infradead.org with esmtp (Exim 4.68 #1 (Red Hat Linux)) id 1JeV6k-0001Fc-Pr for linux-mtd@lists.infradead.org; Wed, 26 Mar 2008 12:51:59 +0000 Message-ID: <47EA4741.2050402@ru.mvista.com> Date: Wed, 26 Mar 2008 15:53:21 +0300 From: Sergei Shtylyov MIME-Version: 1.0 To: Laurent Pinchart Subject: Re: OF compatible MTD platform RAM driver ? References: <200803101606.39184.laurentp@cse-semaphore.com> <200803251823.32039.laurentp@cse-semaphore.com> <200803251914.24021.laurentp@cse-semaphore.com> In-Reply-To: <200803251914.24021.laurentp@cse-semaphore.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: ben@simtec.co.uk, linuxppc-dev@ozlabs.org, Rune Torgersen , linux-mtd@lists.infradead.org, David Gibson List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Laurent Pinchart wrote: >>>Regarding non-volatility nothing prevents a user from using a >>>volatile RAM as an MTD device, but there's little point in doing so. >>>Would it be acceptable for the "linear-nvram" specification >>>not to include > volatile RAM ? ROM chips would be excluded too. Is >>that an issue ? >>We actually use a volatile ram (SRAM) as an MTD device. We use it to >>store info from bootloader and system specific values between resets. > So we're left with two main options. > - Reusing the nvram device type from the Device Support Extensions. Volatile > devices wouldn't be supported, and we'd need a separate device specification > for linear-mapped volatile RAMs. I'm not very happy with that. > - Using another device node with a compatible value set to "linear-ram" (or > something similar). This would support both volatile and non-volatile > devices, and a property could be added to specify if the device is volatile > or not. > I'd go for the second option, and I'd specify a "linear-rom" compatible value > as well while we're at it. > Both volatile and non-volatile RAMs can be handled by the physmap_of MTD > driver. They both use the same map probe type ("map_ram"). Volatility isn't > handled there. > ROMs should be handled by the same driver and should use the "mtd_rom" map > probe type. OK, let's go with it. > As all those devices use the physmap_of MTD driver, what about > using "physmap-ram" and "physmap-rom" as compatibility names ? Heh, we've gone thru "physmap" before -- it was labelled Linux-specific name (well, I'd agree with that). > Best regards, WBR, Sergei