Hi Chris, On 06/04/2015 11:03 PM, Chris Packham wrote:
Hi, I'm working on a new board and one feature it as is a plug-in module with an ADS7830 voltage monitor on it. This will be used during manufacturing to sanity check that various voltage rails are within expected ranges. I have a dts entry for the device as below (with some omissions for the sake of clarity) soc { internal-regs { i2c@11000 { ads7830@48 { compatible = "ads7830"; reg = <0x48>; }; }; }; }; The problem is that when the manufacturing card is not installed the device still shows up in /sys/class/hwmon/hwmon0/ and /sys/bus/i2c/devices/0-0048/ despite it not actually being present. If I was using an old style initialization I could use i2c_new_probed_device() which I think would stop the drivers probe() function from being called Looking at the ads7828_probe() function it doesn't actually do anything with the i2c device before calling hwmon_device_register(). Some hwmon drivers like lm73_probe() do attempt to read from the device and bail if the read fails. I can probably fix my problem by doing something similar in the ads7828_probe(), but there are other drivers that have a similar probe function.
But that would be artificial in this case, and it could not be used to really detect the chip but would only prove that there is a chip at the selected i2c address. This is not really useful.
Is there a better way of getting the devicetree machinery to avoid the call to the driver probe function in the first place?
The easiest solution would probably be to drop the entry from the devicetree file and instantiate the driver manually via sysfs when needed. Another option would be to load a different devicetree file if the chip is plugged in. You might also be able to use a devicetree overlay, but that would probably add too much complexity if the chip is only used in manufacturing. Guenter _______________________________________________ lm-sensors mailing list lm-sensors@xxxxxxxxxxxxxx http://lists.lm-sensors.org/mailman/listinfo/lm-sensors