Re: OF compatible MTD platform RAM driver ?

Laurent Pinchart
2008-03-27T09:13:43Z

On Wednesday 26 March 2008 13:53, Sergei Shtylyov wrote:
> 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).

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 :-)

Could we agree on a name ? I'd like to submit a new patch.

--
Laurent Pinchart
CSE Semaphore Belgium

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