PPC32: Forward-port the /proc/residual stuffs from 2.4. This is

originally by David Monro, updated by Sven Dickert and Hollis Blanchard,
and this version which only vaugly resembles any of those and is by
Leigh Brown <leigh@solinno.co.uk>.

arch/ppc/Config.help

@@ -340,9 +340,16 @@ CONFIG_PREP_RESIDUAL
   other useful pieces of information.  Sometimes this information is
   not present or incorrect.
 
-  Unless you expect to boot on a PReP system, there is not need to
+  Unless you expect to boot on a PReP system, there is no need to
   select Y.
 
+PReP residual data available in /proc/residual
+CONFIG_PROC_PREPRESIDUAL
+  Enabling this option will create a /proc/residual file which allows
+  you to get at the residual data on PReP systems.  You will need a tool
+  (lsresidual) to parse it.  If you aren't on a PReP system, you don't
+  want this.
+
 CONFIG_ADB
   Apple Desktop Bus (ADB) support is for support of devices which
   are connected to an ADB port.  ADB devices tend to have 4 pins.

arch/ppc/config.in

@@ -362,6 +362,7 @@ if [ "$CONFIG_ALL_PPC" = "y" ]; then
    bool 'Support for Open Firmware device tree in /proc' CONFIG_PROC_DEVICETREE
    bool 'Support for RTAS (RunTime Abstraction Services) in /proc' CONFIG_PPC_RTAS
    bool 'Support for PReP Residual Data' CONFIG_PREP_RESIDUAL
+   dep_bool '  Support for reading of PReP Residual Data in /proc' CONFIG_PROC_PREPRESIDUAL $CONFIG_PREP_RESIDUAL
 fi
 
 bool 'Default bootloader kernel arguments' CONFIG_CMDLINE_BOOL

arch/ppc/platforms/residual.c

@@ -876,3 +876,38 @@ PnP_TAG_PACKET __init *PnP_find_large_vendor_packet(unsigned char *p,
 	};
 	return 0; /* not found */
 }
+
+#ifdef CONFIG_PROC_PREPRESIDUAL
+static int proc_prep_residual_read(char * buf, char ** start, off_t off,
+		int count, int *eof, void *data)
+{
+	int n;
+
+	n = res->ResidualLength - off;
+	if (n < 0) {
+		*eof = 1;
+		n = 0;
+	}
+	else {
+		if (n > count)
+			n = count;
+		else
+			*eof = 1;
+
+		memcpy(buf, (char *)res + off, n);
+		*start = buf;
+	}
+
+	return n;
+}
+
+void __init
+proc_prep_residual_init(void)
+{
+	if (res->ResidualLength)
+		create_proc_read_entry("residual", S_IRUGO, NULL,
+					proc_prep_residual_read, NULL);
+}
+
+__initcall(proc_prep_residual_init);
+#endif