hwclock: add get/set parameters option

In kernel 5.16 special ioctls were introduced to get/set RTC parameters.
Add option to get/set parameters into busybox version of hwclock.
Implementation is similar to the one already used in linux-utils hwclock
tool.

Example of parameter get use:
$ hwclock -g 2
The RTC parameter 0x2 is set to 0x2.
$ hwclock --param-get bsm
The RTC parameter 0x2 is set to 0x2.

Example of parameter set use:
$ hwclock -p 2=1
The RTC parameter 0x2 will be set to 0x1.
$ hwclock -p bsm=2
The RTC parameter 0x2 will be set to 0x2.

function                                             old     new   delta
hwclock_main                                         298     576    +278
.rodata                                           105231  105400    +169
packed_usage                                       34541   34576     +35
static.hwclock_longopts                               60      84     +24
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/0 up/down: 506/0)             Total: 506 bytes

Signed-off-by: Andrej Picej <andrej.picej@norik.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/rtc_.h b/include/rtc_.h
index 24ff5363f..782966090 100644
--- a/include/rtc_.h
+++ b/include/rtc_.h
@@ -46,6 +46,17 @@ struct linux_rtc_wkalrm {
         struct linux_rtc_time time;  /* time the alarm is set to */
 };
 
+struct rtc_param {
+        uint64_t param;
+        union {
+                uint64_t uvalue;
+                int64_t svalue;
+                uint64_t ptr;
+        };
+        uint32_t index;
+        uint32_t __pad;
+};
+
 /*
  * ioctl calls that are permitted to the /dev/rtc interface, if
  * any of the RTC drivers are enabled.
@@ -71,12 +82,19 @@ struct linux_rtc_wkalrm {
 #define RTC_WKALM_SET   _IOW('p', 0x0f, struct linux_rtc_wkalrm)/* Set wakeup alarm*/
 #define RTC_WKALM_RD    _IOR('p', 0x10, struct linux_rtc_wkalrm)/* Get wakeup alarm*/
 
+#define RTC_PARAM_GET   _IOW('p', 0x13, struct rtc_param)  /* Get parameter */
+#define RTC_PARAM_SET   _IOW('p', 0x14, struct rtc_param)  /* Set parameter */
+
 /* interrupt flags */
 #define RTC_IRQF 0x80 /* any of the following is active */
 #define RTC_PF 0x40
 #define RTC_AF 0x20
 #define RTC_UF 0x10
 
+#define RTC_PARAM_FEATURES           0
+#define RTC_PARAM_CORRECTION         1
+#define RTC_PARAM_BACKUP_SWITCH_MODE 2
+
 POP_SAVED_FUNCTION_VISIBILITY
 
 #endif