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From: Mike Frysinger <vapier@gentoo.org>
To: u-boot@lists.denx.de
Subject: [U-Boot] [RFC] Make i2c probe opt-outable?
Date: Thu, 17 May 2012 22:48:18 -0400	[thread overview]
Message-ID: <201205172248.20143.vapier@gentoo.org> (raw)
In-Reply-To: <20120517184345.GA23562@bill-the-cat>

On Thursday 17 May 2012 14:43:45 Tom Rini wrote:
> I'd like to propose making 'i2c probe' be a command that is
> opt-out'able.  In the Linux Kernel the notion of probing for devices was
> abandoned a while ago due to, in short, devices misbehaving when
> randomly poked at.  Over in omap24xx_i2c land we changed our probe
> method a while ago from an attempted read to an attempted write as some
> i2c devices would NAK the read.  But now with the am33xx SoM family we
> have a new issue which is that attempting to write to an address doesn't
> immediately issue a NAK so probe sees all addresses as valid and in turn
> leaves the bus upset.  I've worked around this for now by making
> i2c_probe use the read method instead, only on am33xx (so most devices
> would be spotted, but the ones that caused the initial change would not
> show up).  But a possibly better solution is to just make the i2c probe
> command not implemented for am33xx (as you don't have to run i2c probe
> to try and use your device).

i've always seen the "i2c probe" command as a debugging tool, not something 
that you need to do to make things work.  so along those lines, isn't it 
already optional ?  if you don't like it, don't run it :).
-mike
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  reply	other threads:[~2012-05-18  2:48 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-17 18:43 [U-Boot] [RFC] Make i2c probe opt-outable? Tom Rini
2012-05-18  2:48 ` Mike Frysinger [this message]
2012-05-18 16:11   ` Tom Rini
2012-05-18 16:18     ` Mike Frysinger
2012-05-18 18:26     ` Wolfgang Denk
2012-05-18 18:43       ` Tom Rini
2012-05-18 21:52         ` Wolfgang Denk
2012-05-21 16:48           ` Tom Rini

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