linux-kernel - Re: [PATCH] arch/tile: add arch/tile/drivers/ directory with SROM driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <201105211032.51222.arnd@arndb.de>
Date:	Sat, 21 May 2011 10:32:51 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Eric Biederman <ebiederm@...stanetworks.com>
Cc:	Chris Metcalf <cmetcalf@...era.com>, linux-kernel@...r.kernel.org,
	Chris Wright <chrisw@...s-sol.org>,
	"Greg Kroah-Hartman" <gregkh@...e.de>,
	Benjamin Thery <benjamin.thery@...l.net>,
	Phil Carmody <ext-phil.2.carmody@...ia.com>
Subject: Re: [PATCH] arch/tile: add arch/tile/drivers/ directory with SROM driver

On Saturday 21 May 2011 09:46:55 Eric Biederman wrote:
> On Fri, May 20, 2011 at 4:39 PM, Chris Metcalf <cmetcalf@...era.com> wrote:
> > On 5/20/2011 6:40 PM, Eric Biederman wrote:
> > The direct motivation for this case is to "impedance match" to the
> > hypervisor driver for this device, which handles sector management
> > internally, so the Linux device doesn't have to.  Having a 'flush' method
> > avoids excessive re-writes of the same sector for certain access patterns.
> > The only alternatives that I see are to rewrite the tile userspace tools,
> > but they are the way they are because the current model gives good
> > consistency guarantees for writing the boot rom in the presence of
> > arbitrary failure modes; or, to add something like a delayed timer event
> > that allows the Linux driver to notify the hypervisor driver that writes
> > are likely complete and it can write out the last sector.  Neither of these
> > are particularly attractive.
> 
> What is wrong with an mtd driver?
> 
> Looking a bit back into the conversation it appears clear that you are
> talking about something that resembles NOR flash with multiple sectors,
> etc.
> 
> eeproms have random byte access and are typically 256 bytes.  You devices
> doesn't sound anything like an eeprom.

MTD implies that you have low-level access to the NOR flash registers,
which this one doesn't. It's certainly not the right Linux interface
for a high-level flash device, and there is no precedent for this at
all in Linux.

We do have precedent for multiple interfaces that have the same
purpose as this one:

drivers/misc/eeprom/*
drivers/char/ps3flash.c
drivers/char/nwflash.c
drivers/char/bfin-otp.c
arch/powerpc/kernel/rtas_flash.c
drivers/sbus/char/jsflash.c

And then some more that I missed, plus the ones that use MTD.

	Arnd
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/