Messages in this thread | | | Date | Sun, 26 Jan 2014 12:44:38 -0800 | From | Guenter Roeck <> | Subject | Re: lm90 driver no longer working on PCs in 3.13 |
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Hi Jean,
On 01/26/2014 12:13 PM, Jean Delvare wrote: > Hi Guenter, > > Adding Wei Ni to Cc, as he provided the commit which causes problem. > > On Sun, 26 Jan 2014 11:28:16 -0800, Guenter Roeck wrote: >> Hi, >> >> the lm90 driver is no longer working on PCs with the 3.13 kernel ... or at least not without >> special configuration. >> >> This is what I get if I try to instantiate a device on it (max6695): >> >> i2c 1-0018: Driver lm90 requests probe deferral >> i2c i2c-1: new_device: Instantiated device max6695 at 0x18 >> >> The regulator core always returns -EPROBE_DEFER if the platform does not support devicetree >> and if the regulator it is looking for does not exist. Since the driver now requires a mandatory >> regulator (commit 3e0f964f2ad - hwmon: (lm90) Add power control), and the regulator it requests >> does not exist on a PC, the result is not really surprising. I thought the regulator core would >> realize that it has to return a dummy regulator, but apparently that is not the case, or I don't >> know how to configure it. >> >> Any idea what I might need to do to get it working ? > > Me, I really don't know. I seem to remember I tested Wei's patch set on > an emulated ADM1032 chip and it was working fine. So maybe it depends > on the kernel configuration, or something changed on the regulator side > meanwhile. >
The regulator code changed with 3.13; the dummy regulator no longer exists, and the functionality it provided is supposed to be handled automatically. But that only really works on devicetree based systems and otherwise returns -EPROBE_DEFER as mentioned above.
Maybe there is some configuration option, or maybe something needs to be configured from user space. I found neither. In the first case, we should create a dependency for the LM90 driver; in the latter case, we would have to make sure that it is well documented (I'd grumble on that, though - it would result in never ending trouble for us, having to repeatedly explain how this is now supposed to work).
Another possible fix would be to have the regulator core return -ENODEV instead of -EPROBE_DEFER on non-dt systems. No idea if this would be acceptable or even feasible.
Guenter
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