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Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from master device node

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Hi Brian,

On Tue, 27 Oct 2015 18:01:02 -0700
Brian Norris <computersforpeace@gmail.com> wrote:

> On Tue, Oct 27, 2015 at 10:54:46AM -0700, Brian Norris wrote:
> > On Tue, Oct 27, 2015 at 08:42:00AM +0100, Boris Brezillon wrote:
> > > On Mon, 26 Oct 2015 19:31:06 -0700
> > > I like the idea, but how about pushing the solution even further and
> > > killing the ->flash_node field which AFAICT is rendered useless by
> > > your patch?
> > 
> > I suppose we could do that. I do think there's something to be said for
> > layering, though. Historically, we haven't done a very good job of
> > layering in MTD, so low-level drivers often have to poke around in the
> > MTD structures, even if they really should only have to know a few
> > things about their helper subsystem/library, like NAND or SPI NOR. So
> > with that in mind, I think the ->flash_node serves some purpose --
> > drivers can just initialize struct nand_chip/spi_nor and be assured that
> > the NAND/SPI-NOR subsystems will take care of things.
> > 
> > Now, I don't think there's much reason to suspect that we'd have a more
> > complex mapping than 1:1 between struct mtd_info and struct nand_chip or
> > struct spi_nor, so maybe we don't actually need duplicate storage
> > (mtd.dev.of_node and {spi_nor,nand_chip}.flash_node), and the layering
> > is just have these APIs:
> > 
> > 	nand_set_flash_node()
> > 	spi_nor_set_flash_node()
> > 
> > which just call mtd_set_of_node()?
> 
> I looked at this quickly for NAND, and it's hard to do right now because
> of the below quote. The SPI NOR layering is better though, so that
> works. Mind if I defer the dropping the flash_node in NAND but do the
> SPI NOR one?

No, I don't mind (we'll solve that later).

> 
> > Speaking of layering: why do we have NAND drivers initializing mtd->priv
> > for us, yet nand_base just assumes that it points to a struct nand_chip?
> > And why isn't struct mtd_info just embedded in struct nand_chip? Are
> > there ever cases we want more than one (master) MTD per nand_chip? Or
> > vice versa?
> 
> The layering (or lack thereof) make it hard to extract a struct mtd_info
> from a struct nand_chip.

That's true, and that's why we'd better rework a few things (embed
or point to an allocated mtd struct in nand_chip) before trying to
automatically assign mtd->priv to a nand_chip pointer.

Best Regards,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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Thread

[PATCH 0/5] mtd: migrate 'of_node' handling to core, not in mtd_part_parser_data Brian Norris <computersforpeace@gmail.com> - 2015-10-27 03:40 +0100
  [PATCH 3/5] mtd: spi-nor: drop unnecessary partition parser data Brian Norris <computersforpeace@gmail.com> - 2015-10-27 03:40 +0100
  [PATCH 4/5] mtd: drop unnecessary partition parser data Brian Norris <computersforpeace@gmail.com> - 2015-10-27 03:40 +0100
  [PATCH 1/5] mtd: ofpart: grab device tree node directly from master device node Brian Norris <computersforpeace@gmail.com> - 2015-10-27 03:40 +0100
    Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from  master device node Boris Brezillon <boris.brezillon@free-electrons.com> - 2015-10-27 08:50 +0100
      Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from  master device node Brian Norris <computersforpeace@gmail.com> - 2015-10-27 19:00 +0100
        Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from  master device node Brian Norris <computersforpeace@gmail.com> - 2015-10-28 02:10 +0100
          Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from  master device node Boris Brezillon <boris.brezillon@free-electrons.com> - 2015-10-28 09:10 +0100
        Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from  master device node Boris Brezillon <boris.brezillon@free-electrons.com> - 2015-10-28 09:00 +0100
          Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from master device node Marek Vasut <marex@denx.de> - 2015-10-28 17:20 +0100
            Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from  master device node Boris Brezillon <boris.brezillon@free-electrons.com> - 2015-10-28 17:40 +0100
              Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from  master device node Brian Norris <computersforpeace@gmail.com> - 2015-10-28 18:20 +0100
                Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from master device node Robert Jarzmik <robert.jarzmik@free.fr> - 2015-10-28 22:10 +0100
                Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from master device node Marek Vasut <marex@denx.de> - 2015-10-28 23:50 +0100
                Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from master device node Robert Jarzmik <robert.jarzmik@free.fr> - 2015-10-29 07:40 +0100
                Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from  master device node Boris Brezillon <boris.brezillon@free-electrons.com> - 2015-10-29 08:30 +0100
                Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from master device node Marek Vasut <marex@denx.de> - 2015-10-29 18:30 +0100
                Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from  master device node Boris Brezillon <boris.brezillon@free-electrons.com> - 2015-10-29 18:40 +0100
                Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from master device node Robert Jarzmik <robert.jarzmik@free.fr> - 2015-10-29 21:40 +0100
              Re: [PATCH 1/5] mtd: ofpart: grab device tree node directly from master device node Marek Vasut <marex@denx.de> - 2015-10-28 21:40 +0100
  [PATCH 5/5] mtd: drop 'of_node' partition parser data Brian Norris <computersforpeace@gmail.com> - 2015-10-27 03:40 +0100

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