From: Sergei Shtylyov <sshtylyov@ru•mvista.com>
To: David Gibson <david@gibson•dropbear.id.au>
Cc: ben@simtec•co.uk, linux-mtd@lists•infradead.org, linuxppc-dev@ozlabs•org
Subject: Re: OF compatible MTD platform RAM driver ?
Date: Thu, 27 Mar 2008 15:23:46 +0300 [thread overview]
Message-ID: <47EB91D2.60100@ru.mvista.com> (raw)
In-Reply-To: <20080327100304.GC10397@localhost.localdomain>
Hello.
David Gibson wrote:
>>>Laurent Pinchart wrote:
> [snip]
>>> Heh, we've gone thru "physmap" before -- it was labelled Linux-specific
>>>name (well, I'd agree with that).
>>physmap stands for physically mapped. That doesn't sound
>>Linux-specific to me, the fact that the MTD driver has the same name
>>is a pure coincidence. linmap-rom and linmap-rom sound even more
>>Linux-specific :-)
> It may not be Linux specific per se, but it's a bad name, because the
> fact that the device is physically direct mapped isn't a useful
> distinguishing feature of the device.
Yeah, it's not a propery of a device itself (yet, the device would be
useless if this information is not supplied in the tree somehow). Yet remember
the now ungoing discussion about "reg-shift" property for UARTs -- some people
said that the fact that this property may not be a feature of device is
irrelevant WRT the binding. :-)
> Main memory is also direct physically mapped, after all, but that's not what you want to cover
> with this description.
Haven't ever seen the description of memory as a device (unless you mean
the "memory" node which can hardly be considered proper device -- mainly
because of their usual placement at the top of the tree, and not where a RAM
device logically should be in the bus hierarchy).
> In general how a device is wired is described by where it sits in the tree, not by its properties.
Oh, another argument against "reg-shift" in the Xilinx UART quarry... :-)
> It only seems like a usefully distinguishing name because it's the
> Linux "physmap_of" driver that uses it. So in this sense it is a
> Linux specific name after all. In fact, physmap_of is itself very
> badly named - right now it only handles direct mapped mtds, but that's
Yeah, because that's what is what it has been written for.
> not inherent; it could be trivially extended to also instantiate a
> non-direct-mapped device (as long as the underlying mtd layer
> supported it, of course). It bears no relation at all to the
> "physmap" driver, except historical accident.
This driver resides on the "top", device mapping layer of the MTD
hierarchy, and I don't see a point of cramming support for all the possible
mappings into one driver vs doing it as the *separate* specific drivers in
drivers/mtd/mapps/ -- as it has been done in the MTD tree before "the great OF
revolution". This is really strange idea...
WBR, Sergei
next prev parent reply other threads:[~2008-03-27 12:22 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-10 15:06 OF compatible MTD platform RAM driver ? Laurent Pinchart
2008-03-10 17:00 ` Rune Torgersen
2008-03-11 0:45 ` David Gibson
2008-03-11 10:39 ` Laurent Pinchart
2008-03-11 22:40 ` David Gibson
2008-03-25 14:36 ` Laurent Pinchart
2008-03-25 15:29 ` Sergei Shtylyov
2008-03-25 15:51 ` Laurent Pinchart
2008-03-25 16:23 ` Sergei Shtylyov
2008-03-25 16:44 ` Laurent Pinchart
2008-03-25 17:02 ` Sergei Shtylyov
2008-03-25 17:23 ` Laurent Pinchart
2008-03-25 17:37 ` Sergei Shtylyov
2008-03-25 17:56 ` Rune Torgersen
2008-03-25 18:14 ` Laurent Pinchart
2008-03-26 12:53 ` Sergei Shtylyov
2008-03-27 9:13 ` Laurent Pinchart
2008-03-27 10:03 ` David Gibson
2008-03-27 12:23 ` Sergei Shtylyov [this message]
2008-03-28 0:07 ` David Gibson
2008-03-28 12:31 ` Sergei Shtylyov
2008-03-27 14:31 ` Laurent Pinchart
2008-03-28 0:09 ` David Gibson
2008-03-30 18:15 ` Segher Boessenkool
2008-03-30 21:16 ` Paul Mackerras
2008-03-30 22:39 ` Segher Boessenkool
2008-03-31 0:42 ` Paul Mackerras
2008-03-31 0:59 ` Segher Boessenkool
2008-03-31 1:24 ` Segher Boessenkool
2008-03-31 8:21 ` Laurent Pinchart
2008-03-31 12:21 ` Segher Boessenkool
2008-03-26 15:06 ` Segher Boessenkool
2008-03-26 15:40 ` Sergei Shtylyov
2008-03-27 9:24 ` Laurent Pinchart
2008-03-30 18:12 ` Segher Boessenkool
2008-03-26 15:09 ` Segher Boessenkool
2008-03-11 15:00 ` Rune Torgersen
2008-03-11 22:41 ` David Gibson
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