linux-kernel - Re: [lm-sensors] [PATCH] hwmon: (ads7828) Make sample interval configurable

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Message-ID: <20150127233455.0c62457e@endymion.delvare>
Date:	Tue, 27 Jan 2015 23:34:55 +0100
From:	Jean Delvare <jdelvare@...e.de>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Robert Rosengren <robert.rosengren@...s.com>,
	lm-sensors@...sensors.org, Johan Adolfsson <johana@...s.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [lm-sensors] [PATCH] hwmon: (ads7828) Make sample interval
 configurable

On Tue, 27 Jan 2015 12:05:53 -0800, Guenter Roeck wrote:
> On Tue, Jan 27, 2015 at 08:54:34PM +0100, Robert Rosengren wrote:
> > Guenter and Jean, 
> > 
> > To sum up, my problems was related my kernel and hardware configuration, and it now works. Many thanks for your input!
> > 
> > However, the values retrieved from hwmon sysfs is not the same as before the regmap patch. Guenter, the byte swap for the regval retrieved by regmap_read. In what order is the bits returned from that function, because it seems as if I disabled that code I get values as I expect (i.e. before the regmap patch).
> > 
> Trying to understand. Are you saying everything works as expected
> if you keep byte_swap set to false ?
> 
> That might well be, though it might mean that regmap has a bug
> in how it treats i2c word read operations. I'll have to look into it 
> some more.

Remember that SMBus specifies that the LSB comes first (and i2c-core
implement things that way) while real I2C devices typically send the MSB
first. This has always caused confusion. This is why a lot of drivers
need byte-swapping.

-- 
Jean Delvare
SUSE L3 Support
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