Add simple hwconfig infrastructure

This patch implements simple hwconfig infrastructure: an
interface for software knobs to control a hardware.

This is very simple implementation, i.e. it is implemented
via `hwconfig' environment variable. Later we could write
some "hwconfig <enable|disable|list>" commands, ncurses
interface for Award BIOS-like interface, and frame-buffer
interface for AMI GUI[1] BIOS-like interface with mouse
support[2].

Current implementation details/limitations:

1. Doesn't support options dependencies and mutual exclusion.
   We can implement this by integrating apt-get[3] into the
   u-boot. But I didn't bother yet.

2. Since we don't implement hwconfig command, i.e. we're working
   with the environement directly, there is no way to tell that
   toggling a particular option will need a reboot to take
   an effect. So, for now it's advised to always reboot the
   target after modifying hwconfig variable.

3. We support hwconfig options with arguments. For example,

   set hwconfig dr_usb:mode=peripheral,phy_type=ulpi

   That means:
   - dr_usb - enable Dual-Role USB controller;
   - dr_usb:mode=peripheral - USB in Function mode;
   - dr_usb:phy_type=ulpi - USB should work with ULPI PHYs;

The purpose of this simple implementation is to define some
internal API and then we can continue improving user experience
by adding more mature interface, like hwconfig command with
bells and whistles. Or not adding, if we feel that current
interface fits its needs.

[1] http://en.wikipedia.org/wiki/American_Megatrends
[2] Regarding ncurses and GUI with mouse support -- I'm just
    kidding.
[3] The comment regarding apt-get is also a joke, meaning that
    dependency tracking could be non-trivial. For example, for
    enabling HW feature X we may need to disable Y, and turn Z
    into reduced mode (like RMII-only interface for ethernet,
    no MII).

    It's quite trivial to implement simple cases though.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Acked-by: Kim Phillips <kim.phillips@freescale.com>

2 files changed, 211 insertions, 0 deletions

diff --git a/common/Makefile b/common/Makefile
index c8e5d26..c8a997b 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -151,6 +151,7 @@ COBJS-$(CONFIG_VFD) += cmd_vfd.o
 # others
 COBJS-$(CONFIG_DDR_SPD) += ddr_spd.o
 COBJS-$(CONFIG_CMD_DOC) += docecc.o
+COBJS-$(CONFIG_HWCONFIG) += hwconfig.o
 COBJS-$(CONFIG_CONSOLE_MUX) += iomux.o
 COBJS-y += flash.o
 COBJS-$(CONFIG_CMD_KGDB) += kgdb.o
diff --git a/common/hwconfig.c b/common/hwconfig.c
new file mode 100644
index 0000000..e5c60ba
--- /dev/null
+++ b/common/hwconfig.c
@@ -0,0 +1,210 @@
+/*
+ * An inteface for configuring a hardware via u-boot environment.
+ *
+ * Copyright (c) 2009  MontaVista Software, Inc.
+ *
+ * Author: Anton Vorontsov <avorontsov@ru.mvista.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ */
+
+#include <config.h>
+#include <common.h>
+#include <exports.h>
+#include <hwconfig.h>
+#include <linux/types.h>
+#include <linux/string.h>
+
+static const char *hwconfig_parse(const char *opts, size_t maxlen,
+				  const char *opt, char stopch, char eqch,
+				  size_t *arglen)
+{
+	size_t optlen = strlen(opt);
+	char *str;
+	const char *start = opts;
+	const char *end;
+
+next:
+	str = strstr(opts, opt);
+	end = str + optlen;
+	if (end - start > maxlen)
+		return NULL;
+
+	if (str && (str == opts || str[-1] == stopch) &&
+			(*end == stopch || *end == eqch || *end == '\0')) {
+		const char *arg_end;
+
+		if (!arglen)
+			return str;
+
+		if (*end != eqch)
+			return NULL;
+
+		arg_end = strchr(str, stopch);
+		if (!arg_end)
+			*arglen = min(maxlen, strlen(str)) - optlen - 1;
+		else
+			*arglen = arg_end - end - 1;
+
+		return end + 1;
+	} else if (str) {
+		opts = end;
+		goto next;
+	}
+	return NULL;
+}
+
+const char *cpu_hwconfig __attribute__((weak));
+const char *board_hwconfig __attribute__((weak));
+
+static const char *__hwconfig(const char *opt, size_t *arglen)
+{
+	const char *env_hwconfig = getenv("hwconfig");
+
+	if (env_hwconfig)
+		return hwconfig_parse(env_hwconfig, strlen(env_hwconfig),
+				      opt, ';', ':', arglen);
+
+	if (board_hwconfig)
+		return hwconfig_parse(board_hwconfig, strlen(board_hwconfig),
+				      opt, ';', ':', arglen);
+
+	if (cpu_hwconfig)
+		return hwconfig_parse(cpu_hwconfig, strlen(cpu_hwconfig),
+				      opt, ';', ':', arglen);
+
+	return NULL;
+}
+
+/*
+ * hwconfig - query if a particular hwconfig option is specified
+ * @opt:	a string representing an option
+ *
+ * This call can be used to find out whether U-Boot should configure
+ * a particular hardware option.
+ *
+ * Returns non-zero value if the hardware option can be used and thus
+ * should be configured, 0 otherwise.
+ *
+ * This function also returns non-zero value if CONFIG_HWCONFIG is
+ * undefined.
+ *
+ * Returning non-zero value without CONFIG_HWCONFIG has its crucial
+ * purpose: the hwconfig() call should be a "transparent" interface,
+ * e.g. if a board doesn't need hwconfig facility, then we assume
+ * that the board file only calls things that are actually used, so
+ * hwconfig() will always return true result.
+ */
+int hwconfig(const char *opt)
+{
+	return !!__hwconfig(opt, NULL);
+}
+
+/*
+ * hwconfig_arg - get hwconfig option's argument
+ * @opt:	a string representing an option
+ * @arglen:	a pointer to an allocated size_t variable
+ *
+ * Unlike hwconfig() function, this function returns a pointer to the
+ * start of the hwconfig arguments, if option is not found or it has
+ * no specified arguments, the function returns NULL pointer.
+ *
+ * If CONFIG_HWCONFIG is undefined, the function returns "", and
+ * arglen is set to 0.
+ */
+const char *hwconfig_arg(const char *opt, size_t *arglen)
+{
+	return __hwconfig(opt, arglen);
+}
+
+/*
+ * hwconfig_arg_cmp - compare hwconfig option's argument
+ * @opt:	a string representing an option
+ * @arg:	a string for comparing an option's argument
+ *
+ * This call is similar to hwconfig_arg, but instead of returning
+ * hwconfig argument and its length, it is comparing it to @arg.
+ *
+ * Returns non-zero value if @arg matches, 0 otherwise.
+ *
+ * If CONFIG_HWCONFIG is undefined, the function returns a non-zero
+ * value, i.e. the argument matches.
+ */
+int hwconfig_arg_cmp(const char *opt, const char *arg)
+{
+	const char *argstr;
+	size_t arglen;
+
+	argstr = hwconfig_arg(opt, &arglen);
+	if (!argstr || arglen != strlen(arg))
+		return 0;
+
+	return !strncmp(argstr, arg, arglen);
+}
+
+/*
+ * hwconfig_sub - query if a particular hwconfig sub-option is specified
+ * @opt:	a string representing an option
+ * @subopt:	a string representing a sub-option
+ *
+ * This call is similar to hwconfig(), except that it takes additional
+ * argument @subopt. In this example:
+ * 	"dr_usb:mode=peripheral"
+ * "dr_usb" is an option, "mode" is a sub-option, and "peripheral" is its
+ * argument.
+ */
+int hwconfig_sub(const char *opt, const char *subopt)
+{
+	size_t arglen;
+	const char *arg;
+
+	arg = __hwconfig(opt, &arglen);
+	if (!arg)
+		return 0;
+	return !!hwconfig_parse(arg, arglen, subopt, ',', '=', NULL);
+}
+
+/*
+ * hwconfig_subarg - get hwconfig sub-option's argument
+ * @opt:	a string representing an option
+ * @subopt:	a string representing a sub-option
+ * @subarglen:	a pointer to an allocated size_t variable
+ *
+ * This call is similar to hwconfig_arg(), except that it takes an additional
+ * argument @subopt, and so works with sub-options.
+ */
+const char *hwconfig_subarg(const char *opt, const char *subopt,
+			    size_t *subarglen)
+{
+	size_t arglen;
+	const char *arg;
+
+	arg = __hwconfig(opt, &arglen);
+	if (!arg)
+		return NULL;
+	return hwconfig_parse(arg, arglen, subopt, ',', '=', subarglen);
+}
+
+/*
+ * hwconfig_arg_cmp - compare hwconfig sub-option's argument
+ * @opt:	a string representing an option
+ * @subopt:	a string representing a sub-option
+ * @subarg:	a string for comparing an sub-option's argument
+ *
+ * This call is similar to hwconfig_arg_cmp, except that it takes an additional
+ * argument @subopt, and so works with sub-options.
+ */
+int hwconfig_subarg_cmp(const char *opt, const char *subopt, const char *subarg)
+{
+	const char *argstr;
+	size_t arglen;
+
+	argstr = hwconfig_subarg(opt, subopt, &arglen);
+	if (!argstr || arglen != strlen(subarg))
+		return 0;
+
+	return !strncmp(argstr, subarg, arglen);
+}