[RFT PATCH 2/3] bootsource: allow DT aliases and bootrom numbering to differ

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

So far, we had no explicit mapping table between bootsource_instance
and device id numbering in barebox and mostly depended on DT aliases
reflecting the numbering of the bootrom. Add a new bootsource_set()
that optionally consults a mapping table in the DT to arrive at the
correct numbers.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 .../devicetree/bindings/barebox/aliases.rst   |  36 +++++++
 common/bootsource.c                           | 101 +++++++++++++-----
 include/bootsource.h                          |  40 ++++++-
 3 files changed, 149 insertions(+), 28 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/barebox/aliases.rst

diff --git a/Documentation/devicetree/bindings/barebox/aliases.rst b/Documentation/devicetree/bindings/barebox/aliases.rst
new file mode 100644
index 000000000000..527cc85ef696
--- /dev/null
+++ b/Documentation/devicetree/bindings/barebox/aliases.rst
@@ -0,0 +1,36 @@
+barebox DT aliases
+==================
+
+barebox can use the properties in the ``/aliases`` node to arrive
+at deterministic names for devices, e.g.::
+
+.. code-block:: none
+   / {
+   	aliases {
+   		mmc0 = &sdhci;
+   		wdog0 = &iwdg;
+   	};
+   };
+
+will assign the MMC device created from probing the node at ``&sdhci``
+the name ``/dev/mmc0``. Similarly, the watchdog device created from
+probing the node at ``&iwdg`` will be named ``wdog0``.
+
+By default, barebox will assume the aliases in the DT to align with
+the bootsource communicated by the firmware. If this is not the case,
+a device tree override is possible via an
+``/aliases/barebox,bootsource-${bootsource}${bootsource_instance}``
+property:
+
+.. code-block:: none
+
+  &{/aliases} {
+	mmc0 = &sdmmc0;
+	mmc1 = &sdhci;
+	barebox,bootsource-mmc0 = &sdhci;
+	barebox,bootsource-mmc1 = &sdmmc0;
+  };
+
+This will ensure that when booting from MMC, ``/dev/mmc${bootsource_instance}``
+will point at the correct boot device, despite bootrom and board DT alias
+order being different.
diff --git a/common/bootsource.c b/common/bootsource.c
index c37da38f7f99..d74c5e5cbe9f 100644
--- a/common/bootsource.c
+++ b/common/bootsource.c
@@ -33,6 +33,34 @@ static enum bootsource bootsource = BOOTSOURCE_UNKNOWN;
 static int bootsource_instance = BOOTSOURCE_INSTANCE_UNKNOWN;
 const char *bootsource_alias_name = NULL;
 
+const char *bootsource_get_alias_stem(enum bootsource bs)
+{
+	switch (bs) {
+		/*
+		 * For I2C and SPI EEPROMs we set the stem to be 'i2c'
+		 * and 'spi' correspondingly. The resulting alias will
+		 * be pointing at the controller said EEPROM is
+		 * attached to.
+		 *
+		 * NOTE: This code assumes single bootable EEPROM per
+		 * controller
+		 */
+	case BOOTSOURCE_I2C_EEPROM:
+		return bootsource_str[BOOTSOURCE_I2C];
+	case BOOTSOURCE_SPI_EEPROM:
+	case BOOTSOURCE_SPI_NOR:
+		return bootsource_str[BOOTSOURCE_SPI];
+	case BOOTSOURCE_SERIAL:	/* FALLTHROUGH */
+	case BOOTSOURCE_I2C:	/* FALLTHROUGH */
+	case BOOTSOURCE_MMC:	/* FALLTHROUGH */
+	case BOOTSOURCE_SPI:	/* FALLTHROUGH */
+	case BOOTSOURCE_CAN:
+		return bootsource_str[bootsource];
+	default:
+		return NULL;
+	}
+}
+
 /**
  * bootsource_get_alias_name() - Get the name of the bootsource alias
  *
@@ -58,33 +86,9 @@ char *bootsource_get_alias_name(void)
 	if (bootsource_alias_name)
 		return strdup(bootsource_alias_name);
 
-	switch (bootsource) {
-		/*
-		 * For I2C and SPI EEPROMs we set the stem to be 'i2c'
-		 * and 'spi' correspondingly. The resulting alias will
-		 * be pointing at the controller said EEPROM is
-		 * attached to.
-		 *
-		 * NOTE: This code assumes single bootable EEPROM per
-		 * controller
-		 */
-	case BOOTSOURCE_I2C_EEPROM:
-		stem = bootsource_str[BOOTSOURCE_I2C];
-		break;
-	case BOOTSOURCE_SPI_EEPROM:
-	case BOOTSOURCE_SPI_NOR:
-		stem = bootsource_str[BOOTSOURCE_SPI];
-		break;
-	case BOOTSOURCE_SERIAL:	/* FALLTHROUGH */
-	case BOOTSOURCE_I2C:	/* FALLTHROUGH */
-	case BOOTSOURCE_MMC:	/* FALLTHROUGH */
-	case BOOTSOURCE_SPI:	/* FALLTHROUGH */
-	case BOOTSOURCE_CAN:
-		stem = bootsource_str[bootsource];
-		break;
-	default:
+	stem = bootsource_get_alias_stem(bootsource);
+	if (!stem)
 		return NULL;
-	}
 
 	/*
 	 * We expect SoC specific bootsource detection code to properly
@@ -123,6 +127,51 @@ void bootsource_set_raw_instance(int instance)
 		pr_setenv("bootsource_instance", "%d", instance);
 }
 
+int bootsource_of_alias_xlate(enum bootsource bs, int instance)
+{
+	char alias[sizeof("barebox,bootsource-harddisk4294967295")];
+	const char *bootsource_stem;
+	struct device_node *np;
+	int alias_id;
+
+	if (!IS_ENABLED(CONFIG_OFDEVICE))
+		return BOOTSOURCE_INSTANCE_UNKNOWN;
+
+	if (bs == BOOTSOURCE_UNKNOWN ||
+	    instance == BOOTSOURCE_INSTANCE_UNKNOWN)
+		return BOOTSOURCE_INSTANCE_UNKNOWN;
+
+	bootsource_stem = bootsource_get_alias_stem(bs);
+	if (!bootsource_stem)
+		return BOOTSOURCE_INSTANCE_UNKNOWN;
+
+	scnprintf(alias, sizeof(alias), "barebox,bootsource-%s%u",
+		  bootsource_stem, instance);
+
+	np = of_find_node_by_alias(NULL, alias);
+	if (!np)
+		return BOOTSOURCE_INSTANCE_UNKNOWN;
+
+	alias_id = of_alias_get_id(np, bootsource_stem);
+	if (alias_id < 0)
+		return BOOTSOURCE_INSTANCE_UNKNOWN;
+
+	return alias_id;
+}
+
+int bootsource_set(enum bootsource bs, int instance)
+{
+	int alias_id;
+
+	alias_id = bootsource_of_alias_xlate(bs, instance);
+	if (alias_id == BOOTSOURCE_INSTANCE_UNKNOWN)
+		alias_id = instance;
+
+	bootsource_set_raw(bs, alias_id);
+
+	return alias_id;
+}
+
 enum bootsource bootsource_get(void)
 {
 	return bootsource;
diff --git a/include/bootsource.h b/include/bootsource.h
index 390d6f5d2b3a..9ca4fcc525b5 100644
--- a/include/bootsource.h
+++ b/include/bootsource.h
@@ -26,9 +26,45 @@ enum bootsource {
 
 enum bootsource bootsource_get(void);
 int bootsource_get_instance(void);
-void bootsource_set_raw(enum bootsource src, int instance);
-void bootsource_set_raw_instance(int instance);
 void bootsource_set_alias_name(const char *name);
 char *bootsource_get_alias_name(void);
+const char *bootsource_get_alias_stem(enum bootsource bs);
+int bootsource_of_alias_xlate(enum bootsource bs, int instance);
+
+/**
+ * bootsource_set - set bootsource with optional DT mapping table
+ * @bs:	bootrom reported bootsource
+ * @instance: bootrom reported instance
+ *
+ * Returns computed bootsource instace
+ *
+ * Normal bootsource_set_raw_instance() expects numbering used by
+ * bootrom for instance to align with DT aliases, e.g.
+ * $bootsource = "mmc" && $bootsource_instance = 1 -> /aliases/mmc1
+ * bootsource_set() will instead consult
+ * /aliases/barebox,bootsource-mmc1 which may point at a different
+ * device than mmc1. In absence of appropriate barebox,bootsource-*
+ * alias, instance is set without translation.
+ */
+int bootsource_set(enum bootsource bs, int instance);
+
+/**
+ * bootsource_set_raw - set bootsource as-is
+ * @bs:	bootsource to report
+ * @instance: bootsource instance to report
+ *
+ * This sets bootsource and bootsource_instance directly.
+ * Preferably, use bootsource_set in new code.
+ */
+void bootsource_set_raw(enum bootsource src, int instance);
+
+/**
+ * bootsource_set_raw_instance - set bootsource_instance as-is
+ * @bs:	bootrom reported bootsource
+ * @instance: bootrom reported instance
+ *
+ * This directly sets bootsource_instance without changing bootsource.
+ */
+void bootsource_set_raw_instance(int instance);
 
 #endif	/* __BOOTSOURCE_H__ */
-- 
2.30.2