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>

2 files changed, 100 insertions, 5 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
diff --git a/util-linux/hwclock.c b/util-linux/hwclock.c
index a0b7b52bd..d78bfe374 100644
--- a/util-linux/hwclock.c
+++ b/util-linux/hwclock.c
@@ -320,6 +320,70 @@ static void from_sys_clock(const char **pp_rtcname, int utc)
 		close(rtc);
 }
 
+static uint64_t resolve_rtc_param_alias(const char *alias)
+{
+	int n;
+
+	BUILD_BUG_ON(RTC_PARAM_FEATURES != 0
+		|| RTC_PARAM_CORRECTION != 1
+		|| RTC_PARAM_BACKUP_SWITCH_MODE != 2
+	);
+	n = index_in_strings(
+		"features"   "\0"
+		"correction" "\0"
+		"bsm"        "\0"
+		, alias);
+	if (n >= 0)
+		return n;
+	return xstrtoull(alias, 0);
+}
+
+static void get_rtc_param(const char **pp_rtcname, const char *rtc_param)
+{
+	int rtc;
+	struct rtc_param param;
+
+	param.param = resolve_rtc_param_alias(rtc_param);
+
+	rtc = rtc_xopen(pp_rtcname, O_RDONLY);
+
+	xioctl(rtc, RTC_PARAM_GET, &param);
+
+	printf("The RTC parameter 0x%llx is set to 0x%llx.\n",
+		(unsigned long long) param.param, (unsigned long long) param.uvalue);
+
+	if (ENABLE_FEATURE_CLEAN_UP)
+		close(rtc);
+}
+
+static void set_rtc_param(const char **pp_rtcname, char *rtc_param)
+{
+	int rtc;
+	struct rtc_param param;
+	char *eq;
+
+	/* handle param name */
+	eq = strchr(rtc_param, '=');
+	if (!eq)
+		bb_error_msg_and_die("expected <param>=<value>");
+	*eq = '\0';
+	param.param = resolve_rtc_param_alias(rtc_param);
+	*eq = '=';
+
+	/* handle param value */
+	param.uvalue = xstrtoull(eq + 1, 0);
+
+	rtc = rtc_xopen(pp_rtcname, O_WRONLY);
+
+	printf("The RTC parameter 0x%llx will be set to 0x%llx.\n",
+		(unsigned long long) param.param, (unsigned long long) param.uvalue);
+
+	xioctl(rtc, RTC_PARAM_SET, &param);
+
+	if (ENABLE_FEATURE_CLEAN_UP)
+		close(rtc);
+}
+
 // hwclock from util-linux 2.36.1
 // hwclock [function] [option...]
 //Functions:
@@ -346,10 +410,10 @@ static void from_sys_clock(const char **pp_rtcname, int utc)
 
 //usage:#define hwclock_trivial_usage
 //usage:	IF_LONG_OPTS(
-//usage:       "[-swul] [--systz] [-f DEV]"
+//usage:       "[-swul] [--systz] [--param-get PARAM] [--param-set PARAM=VAL] [-f DEV]"
 //usage:	)
 //usage:	IF_NOT_LONG_OPTS(
-//usage:       "[-swult] [-f DEV]"
+//usage:       "[-swult] [-g PARAM] [-p PARAM=VAL] [-f DEV]"
 //usage:	)
 //usage:#define hwclock_full_usage "\n\n"
 //usage:       "Show or set hardware clock (RTC)\n"
@@ -360,6 +424,8 @@ static void from_sys_clock(const char **pp_rtcname, int utc)
 //usage:	IF_LONG_OPTS(
 //usage:     "\n	--systz	Set in-kernel timezone, correct system time"
 //usage:     "\n		if RTC is kept in local time"
+//usage:     "\n	--param-get PARAM	Get RTC parameter"
+//usage:     "\n	--param-set PARAM=VAL	Set RTC parameter"
 //usage:	)
 //usage:     "\n	-f DEV	Use specified device (e.g. /dev/rtc2)"
 //usage:     "\n	-u	Assume RTC is kept in UTC"
@@ -375,11 +441,14 @@ static void from_sys_clock(const char **pp_rtcname, int utc)
 #define HWCLOCK_OPT_SYSTOHC     0x10
 #define HWCLOCK_OPT_SYSTZ       0x20
 #define HWCLOCK_OPT_RTCFILE     0x40
+#define HWCLOCK_OPT_PARAM_GET   0x80
+#define HWCLOCK_OPT_PARAM_SET   0x100
 
 int hwclock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int hwclock_main(int argc UNUSED_PARAM, char **argv)
 {
 	const char *rtcname = NULL;
+	char *param;
 	unsigned opt;
 	int utc;
 #if ENABLE_LONG_OPTS
@@ -391,14 +460,18 @@ int hwclock_main(int argc UNUSED_PARAM, char **argv)
 		"systohc\0"   No_argument "w"
 		"systz\0"     No_argument "t" /* short opt is non-standard */
 		"rtc\0"       Required_argument "f"
+		"param-get\0" Required_argument "g"  /* short opt is non-standard */
+		"param-set\0" Required_argument "p"  /* short opt is non-standard */
 		;
 #endif
 	opt = getopt32long(argv,
-		"^""lurswtf:v" /* -v is accepted and ignored */
+		"^""lurswtf:g:p:v" /* -v is accepted and ignored */
 		"\0"
-		"r--wst:w--rst:s--wrt:t--rsw:l--u:u--l",
+		"r--wstgp:w--rstgp:s--wrtgp:t--rswgp:g--rswtp:p--rswtg:l--u:u--l",
 		hwclock_longopts,
-		&rtcname
+		&rtcname,
+		&param,
+		&param
 	);
 
 	/* If -u or -l wasn't given, check if we are using utc */
@@ -413,6 +486,10 @@ int hwclock_main(int argc UNUSED_PARAM, char **argv)
 		from_sys_clock(&rtcname, utc);
 	else if (opt & HWCLOCK_OPT_SYSTZ)
 		set_kernel_timezone_and_clock(utc, NULL);
+	else if (opt & HWCLOCK_OPT_PARAM_GET)
+		get_rtc_param(&rtcname, param);
+	else if (opt & HWCLOCK_OPT_PARAM_SET)
+		set_rtc_param(&rtcname, param);
 	else
 		/* default HWCLOCK_OPT_SHOW */
 		show_clock(&rtcname, utc);