linux-kernel - Re: (EXT) Re: (EXT) Re: [PATCH 1/2] mtd: spi-nor: micron-st: sync flags of mt25ql02g and mt25qu02g with other mt25q

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Message-ID: <0e2ad27b00d85c1dfa489d91b54d2a3af41f5edb.camel@ew.tq-group.com>
Date:   Thu, 07 Oct 2021 09:18:22 +0200
From:   Matthias Schiffer <matthias.schiffer@...tq-group.com>
To:     Michael Walle <michael@...le.cc>
Cc:     Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Pratyush Yadav <p.yadav@...com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: (EXT) Re: (EXT) Re: [PATCH 1/2] mtd: spi-nor: micron-st: sync
 flags of mt25ql02g and mt25qu02g with other mt25q

On Thu, 2021-10-07 at 09:08 +0200, Michael Walle wrote:
> Am 2021-10-06 14:32, schrieb Matthias Schiffer:
> > On Tue, 2021-07-27 at 09:09 +0200, Michael Walle wrote:
> > > Am 2021-07-23 13:27, schrieb Matthias Schiffer:
> > > > All mt25q variants have the same features.
> > > > 
> > > > Unlike the smaller variants, no n25q with 2G exists, so we don't need
> > > > to
> > > > match on the extended ID to distinguish n25q and mt25q series for these
> > > > models.
> > > 
> > > But why shouldn't we? What if there will be another flash with
> > > the same first three id bytes?
> > 
> > How do you suggest we proceed here? At the moment there are entries
> > matching on 0x20b[ab]22 (ignoring the extended ID) with the name
> > mt25q[lu]02g.
> > 
> > Should I change these entries to match on on the extended ID
> > 0x20b[ab]22 / 0x104400 instead when I add the bits for the features
> > specific to the variant, removing support for other 0x20b[ab]22
> > variants that may or may not actually exist? Keeping both entries (with
> > and without extended ID match) would preserve compatiblity with such
> > variants, but this approach seems problematic to me as well, as I can't
> > even give a name to the more generic entries (and there is no natural
> > extension of the n25q naming scheme to a 2G variant).
> 
> Mh, what do you think of adding three entries and make the last one,
> the one with the short id, as a fallback so to speak. This should
> retrain backwards compatibility, right? It should probably have a
> comment because the order will matter then.
> 
> -michael

Is it okay for multiple entries to use the same value for the "name"
field? In the existing definitions I couldn't find any example of
different ID matches mapping to the same name.