From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailrelay005.isp.belgacom.be (mailrelay005.isp.belgacom.be [195.238.6.171]) by ozlabs.org (Postfix) with ESMTP id B79F0DE0C3 for ; Wed, 26 Mar 2008 05:14:30 +1100 (EST) From: Laurent Pinchart To: "Rune Torgersen" Subject: Re: OF compatible MTD platform RAM driver ? Date: Tue, 25 Mar 2008 19:14:20 +0100 References: <200803101606.39184.laurentp@cse-semaphore.com> <200803251823.32039.laurentp@cse-semaphore.com> In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart1972833.p6L5KqdjO2"; protocol="application/pgp-signature"; micalg=pgp-sha1 Message-Id: <200803251914.24021.laurentp@cse-semaphore.com> Cc: ben@simtec.co.uk, David Gibson , linux-mtd@lists.infradead.org, linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --nextPart1972833.p6L5KqdjO2 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline On Tuesday 25 March 2008 18:56, Rune Torgersen wrote: > Laurent Pinchart wrote: > > On Tuesday 25 March 2008 18:02, Sergei Shtylyov wrote: > >> Laurent Pinchart wrote: > >>=20 > > Regarding non-volatility nothing prevents a user from using a=20 > > 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 ? >=20 > 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. =2D Reusing the nvram device type from the Device Support Extensions. Volat= ile=20 devices wouldn't be supported, and we'd need a separate device specificatio= n=20 for linear-mapped volatile RAMs. I'm not very happy with that. =2D Using another device node with a compatible value set to "linear-ram" (= or=20 something similar). This would support both volatile and non-volatile=20 devices, and a property could be added to specify if the device is volatile= =20 or not. I'd go for the second option, and I'd specify a "linear-rom" compatible val= ue=20 as well while we're at it. Both volatile and non-volatile RAMs can be handled by the physmap_of MTD=20 driver. They both use the same map probe type ("map_ram"). Volatility isn't= =20 handled there. ROMs should be handled by the same driver and should use the "mtd_rom" map= =20 probe type. As all those devices use the physmap_of MTD driver, what about=20 using "physmap-ram" and "physmap-rom" as compatibility names ? Best regards, =2D-=20 Laurent Pinchart CSE Semaphore Belgium Chauss=E9e de Bruxelles, 732A B-1410 Waterloo Belgium T +32 (2) 387 42 59 =46 +32 (2) 387 42 75 --nextPart1972833.p6L5KqdjO2 Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (GNU/Linux) iD8DBQBH6UEA8y9gWxC9vpcRAnAdAKCl+R9yUIF3XoE+NEyaD1HywCpcBQCePN+j 0QtPBwPn8tCK7C2F4CBt8Is= =aT37 -----END PGP SIGNATURE----- --nextPart1972833.p6L5KqdjO2--