Re: [PATCH] devicetree/bindings: Add binding for micron n25q512a memory

[Scott Wood <scottwood@freescale.com>]

On Thu, 2014-07-03 at 23:08 -0500, Jain Priyanka-B32167 wrote:
> 
> > -----Original Message-----
> > From: Wood Scott-B07421
> > Sent: Friday, July 04, 2014 3:40 AM
> > To: Jain Priyanka-B32167
> > Cc: devicetree@vger.kernel.org; linuxppc-dev@lists.ozlabs.org; linux-
> > spi@vger.kernel.org; linux-mtd@lists.infradead.org
> > Subject: Re: [PATCH] devicetree/bindings: Add binding for micron n25q512a
> > memory
> > 
> > On Thu, 2014-07-03 at 15:42 +0530, Priyanka Jain wrote:
> > > -Micron n25q512a memory is supported by m25p80 driver.
> > >  Add compatible field required to support n25q512a in m25p80.txt -Add
> > > micron to the vendor-prefixes.txt file
> > >
> > > Signed-off-by: Priyanka Jain <Priyanka.Jain@freescale.com>
> > > ---
> > >  Documentation/devicetree/bindings/mtd/m25p80.txt   |    1 +
> > >  .../devicetree/bindings/vendor-prefixes.txt        |    1 +
> > >  2 files changed, 2 insertions(+), 0 deletions(-)
> > 
> > Why did you send this to the ppc list but not the spi or mtd lists?
> > 
> [Jain Priyanka-B32167] Sorry, I missed that
> > I'm having a hard time following the flow of how these SPI devices get
> > bound -- is the compatible involved at all?  I don't see this string
> > (with vendor prefix included) in the driver.  I do see a table that
> > contains what looks like device IDs.  If the device can report its id,
> > shouldn't we rely on that rather than device tree compatible?
> > 
> > -Scott
> [Jain Priyanka-B32167]
> Spi driver has a check to device name corresponding to device-id and compare to what is passed in dts string.

Please go into more detail.  I don't see where the string
"micron,n25q512a" appears in the current kernel.  I do see "n25q512a",
but how does that compare successfully with the version of the string
that has a vendor compatible?

Again, is there a device ID that can be read at runtime?  Is there a
compatible string that represents a common programming interface?

> New checkpatch script search for exact string match in binding folder. So, I have added this in example.

That check has a lot of false positives when it comes to compatible
strings for specific chips that don't need to be specifically mentioned
in a more generic binding.

-Scott