RFC: Intel QST driver

I've written a driver for the Intel Quiet System Technology (QST) function of the Management Engine Interface found on recent Intel chipsets.

The git repo can be found here:

http://mose.dyndns.org/mei.git

A few questions / observations,

1) The code was developed and tested on 2.6.39. I would hope it compiles and runs on 3.x but I haven't tried it.

2) The main hwmon code is in qst-hwmon.c. This implements QST v1, I don't have access to hardware that supports v2. I would imagine that implementing v2 would result in a new module (qst2-hwmon) which would be almost identical.

3) I've gone a bit overboard with preprocessor macros but it does mean that the amount of duplicated code is kept to a minimum.

3) I've not implemented any PWM methods yet.

4) I don't believe the MEI (HECI) implementation that Intel have already submitted to the mainline kernel is usable by other kernel modules. I have re-implemented it in a way that is accessible to either the kernel or userspace.

5) I had to patch libsensors to work with a new bus type

diff -ur lm_sensors-3.3.1.org//lib/sysfs.c lm_sensors-3.3.1/lib/sysfs.c
@@ -701,6 +701,12 @@
                 /* As of kernel 2.6.32, the hid device names don't look 

good */

                 entry.chip.bus.nr = bus;
                 entry.chip.addr = id;
+       } else
+       if (subsys && !strcmp(subsys, "intel-mei") &&
+           sscanf(dev_name, "mei%d:%d", &bus, &fn) = 2) {
+               entry.chip.bus.type = SENSORS_BUS_TYPE_PCI;
+               entry.chip.bus.nr = bus;
+               entry.chip.addr = fn;
         } else {
                 /* Ignore unknown device */
                 err = 0;

surely this sort of knowledge belongs in the driver not userspace? Could drivers not provide another set of sysfs attributes which expose bus type, number, addr etc?

Please let me know if there's any changes or improvements I can make to it.

Simon

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Hi Simon,

2.6.39 is pretty old. It doesn't include the new mei driver (which is now in drivers/misc/mei).

Is it that much different that it would require a separate driver, especially if it is almost identical ?

It also hides possible error cases, though, and makes review very complicated. You would be better off using function parameters as much as possible. Plus, after all, it is not correct that you avoid duplicate code. You only avoid duplicate source code. Fore that, the additional cost (in terms of risk and maintainability) is pretty high.

2.6.39 does not include the new mei driver, so I don't think you can make that claim.

I would suggest to have a look into the new driver and work with its maintainer to make it better suitable for other drivers if needed. Its main deficiency, as far as I could see when I looked into it, is that it doesn't support out-of-directory drivers very well - which means the hwmon driver might have to reside in drivers/misc/mei instead of drivers/hwmon. Not an optimal solution, but better than nothing.

You might want to run your code through checkpatch and fix all errors and warnings. The major problem, though, is that we can not have two instances of mei core code in the kernel.

Copying the mei driver maintainer and the kernel mailing list for additional input.

Thanks,
Guenter

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We are working on adding possibility of stacking another drivers
above the MEI
in these days. I cannot commit to specific time line yet but it is on the way.

Thanks
Tomas

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