[PATCH v2 1/9] introduce SoC UID

[Sascha Hauer <s.hauer@pengutronix.de>]

Most SoCs have a unique ID (UID) which can be used to identify a
particular SoC instance. This is exposed to the environment by some SoC
drivers as soc0.serial_number like also done in Linux. The SoC UID can
also conveniently be used to generate a unique machine_id on systems
with a readonly rootfs. The two usecases require the SoC UID in different
formats. While machine_id_set_hashable() takes a binary representation
of the SoC UID, soc0.serial_number is a string. The conversion from the
binary representation to the string is SoC specific, some SoCs interpret
the binary data as a byte array (AM62x for example), others interpret it
as words of different lengths in different endianesses (i.MX). Others
even print the binary data as decimal (qcom).

Needing a SoC driver for providing the SoC UID is an unlucky choice as
some SoCs do not have a SoC driver, but instead read the SoC UID in
their eFuse driver in drivers/nvmem (STM32MP bsec). These drivers
provide hashable data to generate a machine_id, but do not expose the
SoC ID.

This patch introduces barebox_set_soc_uid(). This function provides a
new environment variable global.soc_uid which contains the SoC UID.
It also passes the SoC UID to machine_id_set_hashable() for generating a
machine_id. To accomodate for different string representations of the
binary data barebox_set_soc_uid() takes both the binary data and a
string in the SoCs preferred format of the same data.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 common/misc.c          | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++
 include/barebox-info.h |  4 ++++
 2 files changed, 62 insertions(+)

diff --git a/common/misc.c b/common/misc.c
index 0af5a9cf30cdb952063974969c368061420a6e2b..ef6687f01389beaed44fc446b25ec5f21e712366 100644
--- a/common/misc.c
+++ b/common/misc.c
@@ -16,6 +16,7 @@
 #include <restart.h>
 #include <poweroff.h>
 #include <string.h>
+#include <machine_id.h>
 #include <linux/stringify.h>
 
 int errno;
@@ -252,6 +253,63 @@ const char *barebox_get_serial_number(void)
 
 BAREBOX_MAGICVAR(global.serial_number, "Board serial number");
 
+static char *soc_uid_str;
+static void *soc_uid;
+static size_t soc_uid_len;
+
+/*
+ * barebox_set_soc_uid - set a Unique SoC ID
+ *
+ * Set a Unique SoC ID. The ID is usually read from SoC internal eFuses. It
+ * can vary in length on different SoCs and can have different canonical hex
+ * representations. @uidstr can be NULL in which case uidbuf is interpreted
+ * as a byte array.
+ *
+ * barebox uses the SoC ID to generate a machine_id and exports it to the
+ * environment via global.soc_uid.
+ *
+ * In Linux the serial number is exported as /sys/devices/soc0/serial_number
+ * which should generally have the same format as *uidstr.
+ */
+void barebox_set_soc_uid(const char *uidstr, const void *uidbuf, size_t len)
+{
+	if (soc_uid_str) {
+		pr_warn("SoC UID already set. Ignoring\n");
+		return;
+	}
+
+	soc_uid = xmemdup(uidbuf, len);
+	soc_uid_len = len;
+
+	if (uidstr) {
+		soc_uid_str = xstrdup(uidstr);
+	} else {
+		soc_uid_str = xzalloc(len * 2 + 1);
+		bin2hex(soc_uid_str, uidbuf, len);
+	}
+
+	machine_id_set_hashable(uidbuf, len);
+
+	globalvar_add_simple_string("soc_uid", &soc_uid_str);
+}
+BAREBOX_MAGICVAR(global.soc_uid, "SoC Unique ID");
+
+const char *barebox_get_soc_uid(void)
+{
+	return soc_uid_str;
+}
+
+int barebox_get_soc_uid_bin(const void **buf, size_t *len)
+{
+	if (!soc_uid)
+		return -ENOENT;
+
+	*buf = soc_uid;
+	*len = soc_uid_len;
+
+	return 0;
+}
+
 #ifdef CONFIG_OFTREE
 static char *of_machine_compatible;
 
diff --git a/include/barebox-info.h b/include/barebox-info.h
index bcceb7b0e0211c8c7dccd6b9f480c9fbc13dcf63..898fb493b6348ee64670f928a3598a7c3d277554 100644
--- a/include/barebox-info.h
+++ b/include/barebox-info.h
@@ -25,6 +25,10 @@ bool barebox_hostname_is_valid(const char *s);
 const char *barebox_get_serial_number(void);
 void barebox_set_serial_number(const char *);
 
+void barebox_set_soc_uid(const char *uidstr, const void *uidbuf, size_t len);
+const char *barebox_get_soc_uid(void);
+int barebox_get_soc_uid_bin(const void **buf, size_t *len);
+
 #ifdef CONFIG_OFTREE
 void barebox_set_of_machine_compatible(const char *);
 const char *barebox_get_of_machine_compatible(void);

-- 
2.47.3