[src/trunk]: src/sys/dev/i2c remove some unused code, add comments for credit...

[macallan <macallan%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/38ca8fc2246a
branches:  trunk
changeset: 321303:38ca8fc2246a
user:      macallan <macallan%NetBSD.org@localhost>
date:      Fri Mar 09 22:27:15 2018 +0000

description:
remove some unused code, add comments for credits & explanations

diffstat:

 sys/dev/i2c/adadc.c |  37 ++++++++++++++++++++++++++++---------
 1 files changed, 28 insertions(+), 9 deletions(-)

diffs (108 lines):

diff -r 3a203ba0d84f -r 38ca8fc2246a sys/dev/i2c/adadc.c
--- a/sys/dev/i2c/adadc.c       Fri Mar 09 21:49:55 2018 +0000
+++ b/sys/dev/i2c/adadc.c       Fri Mar 09 22:27:15 2018 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: adadc.c,v 1.1 2018/03/09 20:16:54 macallan Exp $ */
+/* $NetBSD: adadc.c,v 1.2 2018/03/09 22:27:15 macallan Exp $ */
 
 /*-
  * Copyright (c) 2018 Michael Lorenz
@@ -26,10 +26,15 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
-/* a driver for Analog Devices AD7417 temperature sensors / ADCs */
+/*
+ * a driver for Analog Devices AD7417 temperature sensors / ADCs
+ * very much macppc only for now since we need calibaration data to make sense
+ * of the ADC inputs
+ * info on how to get these from FreeBSD and Linux
+ */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: adadc.c,v 1.1 2018/03/09 20:16:54 macallan Exp $");
+__KERNEL_RCSID(0, "$NetBSD: adadc.c,v 1.2 2018/03/09 22:27:15 macallan Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -93,6 +98,7 @@
        NULL
 };
 
+/* calibaration table from Darwin via Linux */
 static int slope[5] = {0, 0, 0x0320, 0x00a0, 0x1f40};
 
 static int
@@ -101,7 +107,11 @@
        struct i2c_attach_args *ia = aux;
 
        if (ia->ia_name == NULL) {
-               /* no ID registers on this chip */
+               /*
+                * XXX
+                * this driver is pretty much useless without OF, should
+                * probably remove this
+                */
                if ((ia->ia_addr & 0x2b) == 0x2b)
                        return 1;
                return 0;
@@ -118,7 +128,6 @@
        envsys_data_t *s;
        int error, ch, cpuid;
        uint32_t eeprom[40];
-       uint8_t cmd, data;
        char loc[256];
        int which_cpu;
 
@@ -129,16 +138,17 @@
        aprint_naive("\n");
        aprint_normal(": AD7417\n");
 
-       cmd = ADADC_CONFIG;
-       error = iic_exec(sc->sc_i2c, I2C_OP_READ_WITH_STOP,
-           sc->sc_addr, &cmd, 1, &data, 1, 0);
-
        sc->sc_sme = sysmon_envsys_create();
        sc->sc_sme->sme_name = device_xname(self);
        sc->sc_sme->sme_cookie = sc;
        sc->sc_sme->sme_refresh = adadc_sensors_refresh;
        sc->sc_nsensors = 0;
 
+       /*
+        * XXX
+        * without OpenFirmware telling us how to interpret the ADC inputs we
+        * should probably just expose the temperature and four ENVSYS_INTEGERs
+        */
        which_cpu = 0;
        ch = OF_child(ia->ia_cookie);
        while (ch != 0) {
@@ -146,6 +156,10 @@
                        int reg = 0;
                        OF_getprop(ch, "reg", &reg, sizeof(reg));
                        s = &sc->sc_sensors[sc->sc_nsensors];
+                       /*
+                        * this setup matches my 2x 2.5GHz PCI-X G5, Linux and
+                        * FreeBSD hardcode these as well so we should be safe
+                        */
                        switch (reg) {
                        case 0:
                                if (strstr(loc, "CPU B") != NULL)
@@ -220,6 +234,10 @@
                        /* 16.16 fixed point */
                        edata->value_cur = (temp >> 12) * 62500 + 273150000;
                } else {
+                       /*
+                        * the input is 10bit, so converting to 8.4 fixed point
+                        * is more than enough
+                        */
                        int temp = rdata * slope[edata->private];
                        edata->value_cur = (temp >> 12) * 62500;
                }
@@ -228,6 +246,7 @@
                /* just read the temperature register */
                error = iic_exec(sc->sc_i2c, I2C_OP_READ_WITH_STOP,
                    sc->sc_addr, &cmd, 1, &data, 2, 0);
+               /* 8.2 bit fixed point Celsius -> microkelvin */
                edata->value_cur = ((data >> 6) * 250000) + 273150000;
        }
        iic_release_bus(sc->sc_i2c, 0);