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From: Johan Hovold <johan@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: "Fabio M. De Francesco" <fmdefrancesco@gmail.com>,
	Alex Elder <elder@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	greybus-dev@lists.linaro.org, linux-staging@lists.linux.dev,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4] staging: greybus: Convert uart.c from IDR to XArray
Date: Tue, 31 Aug 2021 10:16:42 +0200	[thread overview]
Message-ID: <YS3laqvwXE9XoAD/@hovoldconsulting.com> (raw)
In-Reply-To: <YSzdtzH1GdZqt66G@casper.infradead.org>

On Mon, Aug 30, 2021 at 02:31:35PM +0100, Matthew Wilcox wrote:
> On Mon, Aug 30, 2021 at 02:33:05PM +0200, Johan Hovold wrote:
> > On Mon, Aug 30, 2021 at 01:16:07PM +0100, Matthew Wilcox wrote:
> > > On Mon, Aug 30, 2021 at 01:52:48PM +0200, Johan Hovold wrote:
> > > > Whether the API is better is debatable. As I said, almost no drivers use
> > > > the new XArray interface, and perhaps partly because the new interface
> > > > isn't as intuitive as has been claimed (e.g. xa_load() instead of
> > > > ida_find()). And IDR/IDA isn't marked/documented as deprecated as far as
> > > > I know.

> > > Why do you think that idr_find() is more intuitive than xa_load()?
> > > The 'find' verb means that you search for something.  But it doesn't
> > > search for anything; it just returns the pointer at that index.
> > > 'find' should return the next non-NULL pointer at-or-above a given
> > > index.
> > 
> > We're looking up a minor number which may or may not exist. "Find" (or
> > "lookup" or "search") seems to describe this much better than "load"
> > (even if that may better reflect the implementation of XArray).
> 
> It's not the _implementation_ that it fits, it's the _idiom_.
> The implementation is a lookup in a trie.  The idiom of the XArray
> is that it's a sparse array, and so it's a load.

Ok, but it still stands out in the conversions since it is in no way
obvious that idr_find() should be replaced by xa_load() from just
looking at the diff. You need to look up the interface for that.

> > And no, I would not expect a find implementation to return the next
> > entry if the requested entry does not exist (and neither does idr_find()
> > or radix_tree_lookup()).
> 
> Oh dear.  You've been corrupted by the bad naming of the IDR functions
> ;-(

Heh. Don't flatter yourself. Just look up any text book on data
structures.

Johan

      reply	other threads:[~2021-08-31  8:16 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-29  9:22 Fabio M. De Francesco
2021-08-30  9:12 ` Johan Hovold
2021-08-30 11:10   ` Fabio M. De Francesco
2021-08-30 11:52     ` Johan Hovold
2021-08-30 12:16       ` Matthew Wilcox
2021-08-30 12:33         ` Johan Hovold
2021-08-30 13:16           ` Fabio M. De Francesco
2021-08-30 13:20           ` [greybus-dev] " Alex Elder
2021-08-31  8:07             ` Johan Hovold
2021-08-31 10:42               ` Alex Elder
2021-08-31 11:51                 ` Johan Hovold
2021-08-31 11:50               ` Fabio M. De Francesco
2021-08-31 12:18                 ` Johan Hovold
2021-09-01 12:09                 ` Alex Elder
2021-09-01 13:56                   ` Fabio M. De Francesco
2021-09-01 14:29                     ` Matthew Wilcox
2021-09-01 15:39                       ` Fabio M. De Francesco
2021-08-30 13:31           ` Matthew Wilcox
2021-08-31  8:16             ` Johan Hovold [this message]

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