[src/trunk]: src/sys/arch/sparc64/dev When matching, try a read in case this ...

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

details:   https://anonhg.NetBSD.org/src/rev/85d37afedf19
branches:  trunk
changeset: 946636:85d37afedf19
user:      jdc <jdc%NetBSD.org@localhost>
date:      Sat Dec 05 15:08:21 2020 +0000

description:
When matching, try a read in case this is an optional device and isn't
actually present.

diffstat:

 sys/arch/sparc64/dev/pcf8591_envctrl.c |  26 ++++++++++++++++++++++----
 1 files changed, 22 insertions(+), 4 deletions(-)

diffs (49 lines):

diff -r 17b3a5f8e1bb -r 85d37afedf19 sys/arch/sparc64/dev/pcf8591_envctrl.c
--- a/sys/arch/sparc64/dev/pcf8591_envctrl.c    Sat Dec 05 15:02:29 2020 +0000
+++ b/sys/arch/sparc64/dev/pcf8591_envctrl.c    Sat Dec 05 15:08:21 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pcf8591_envctrl.c,v 1.11 2020/10/31 13:17:34 jdc Exp $ */
+/*     $NetBSD: pcf8591_envctrl.c,v 1.12 2020/12/05 15:08:21 jdc Exp $ */
 /*     $OpenBSD: pcf8591_envctrl.c,v 1.6 2007/10/25 21:17:20 kettenis Exp $ */
 
 /*
@@ -19,7 +19,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pcf8591_envctrl.c,v 1.11 2020/10/31 13:17:34 jdc Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pcf8591_envctrl.c,v 1.12 2020/12/05 15:08:21 jdc Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -99,10 +99,28 @@
 ecadc_match(device_t parent, cfdata_t cf, void *aux)
 {
        struct i2c_attach_args *ia = aux;
+       struct ecadc_softc sc;
        int match_result;
+       u_int8_t junk;
+
+       if (!iic_use_direct_match(ia, cf, compat_data, &match_result))
+               return 0;
 
-       if (iic_use_direct_match(ia, cf, compat_data, &match_result))
-               return match_result;
+       /* Try a read so that we don't match on optional components */
+       if (match_result) {
+               sc.sc_tag = ia->ia_tag;
+               sc.sc_addr = ia->ia_addr;
+
+               iic_acquire_bus(sc.sc_tag, 0);
+               if (iic_exec(sc.sc_tag, I2C_OP_READ_WITH_STOP, sc.sc_addr,
+                   NULL, 0, &junk, 1, 0)) {
+                       iic_release_bus(sc.sc_tag, 0);
+                       return 0;
+               } else {
+                       iic_release_bus(sc.sc_tag, 0);
+                       return match_result;
+               }
+       }
 
        /* This driver is direct-config only. */