linux-kernel - Re: [BUG ?] regmap: debugfs: WARN

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Message-ID: <20150615094922.GB18309@sirena.org.uk>
Date:	Mon, 15 Jun 2015 10:49:22 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Sergej Sawazki <ce3a@....de>
Cc:	gregkh@...uxfoundation.org, w.sang@...gutronix.de,
	wsa@...-dreams.de, linux-kernel@...r.kernel.org
Subject: Re: [BUG ?] regmap: debugfs: WARN_ON at regmap-debugfs.c:151

On Sat, Jun 13, 2015 at 03:21:02PM +0200, Sergej Sawazki wrote:

> when I try to read the register values of a i2c ASoC codec through
> debugfs, (eg: cat /sys/kernel/debug/regmap/1-001a/registers)
> I am getting an WARN_ON at drivers/base/regmap/regmap-debugfs.c:151.

Please provide some plain text description of which line of code you're
referring to when reporting things - line numbers do change as things
move on (though I see this one).

> I did some debugging and found that regmap_readable(), at regmap-
> debugfs.c:109, returns "false" for all registers, hence the
> debugfs_off_cache list remains empty and we get an warning in line 151.

We need to change that code to special case write only register maps
like this and just skip having a cache for those devices.  They normally
have very small register maps anyway so it shouldn't have too big an
impact on performance.

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