cmd: setexpr: add format string handling

Add format string handling operator to the setexpr command.
It allows to use C or Bash like format string expressions to be
evaluated with the result being stored inside the environment variable
name.

  setexpr <name> fmt <format> [value]...

The following example

  setexpr foo fmt "%d, 0x%x" 0x100 ff

will result in $foo being set to "256, 0xff".

Signed-off-by: Roland Gaudig <[email protected]>
Reviewed-by: Simon Glass <[email protected]>

Author: Roland Gaudig

MAINTAINERS

@@ -1050,6 +1050,11 @@ F:	arch/sandbox/
 F:	doc/arch/sandbox.rst
 F:	include/dt-bindings/*/sandbox*.h
 
+SETEXPR
+M:	Roland Gaudig <[email protected]>
+S:	Maintained
+F:	cmd/printf.c
+
 SH
 M:	Marek Vasut <[email protected]>
 M:	Nobuhiro Iwamatsu <[email protected]>

cmd/Kconfig

@@ -1414,6 +1414,14 @@ config CMD_SETEXPR
 	  Also supports loading the value at a memory location into a variable.
 	  If CONFIG_REGEX is enabled, setexpr also supports a gsub function.
 
+config CMD_SETEXPR_FMT
+	bool "setexpr_fmt"
+	default n
+	depends on CMD_SETEXPR
+	help
+	  Evaluate format string expression and store result in an environment
+	    variable.
+
 endmenu
 
 menu "Android support commands"

cmd/Makefile

@@ -141,6 +141,7 @@ obj-$(CONFIG_CMD_SF) += sf.o
 obj-$(CONFIG_CMD_SCSI) += scsi.o disk.o
 obj-$(CONFIG_CMD_SHA1SUM) += sha1sum.o
 obj-$(CONFIG_CMD_SETEXPR) += setexpr.o
+obj-$(CONFIG_CMD_SETEXPR_FMT) += printf.o
 obj-$(CONFIG_CMD_SPI) += spi.o
 obj-$(CONFIG_CMD_STRINGS) += strings.o
 obj-$(CONFIG_CMD_SMC) += smccc.o