Re: Udev support for EDD

[Kay Sievers <kay.sievers@vrfy.org>]

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On Thu, Sep 01, 2005 at 03:15:38PM -0500, John_Hull@Dell.com wrote:
> I'd like to get feedback from this mailing list on a small project I've
> been working on, which is adding support to udev for the persistent
> naming of BIOS disk devices via EDD. EDD is mechanism to match x86 BIOS
> device names (e.g. int13 device 80h) to Linux device names (e.g.
> /dev/sda, /dev/hda), and a kernel module to support this was written by
> Matt Domsch (see http://linux.dell.com/projects.shtml#edd for more
> information). The EDD module makes device information available in
> /sys/firmware/edd/int13_dev8*/, with the directory containing various
> information for each device. For example, the first BIOS disk drive
> would be int13_dev80, the second int13_dev81, etc. 

Nice to see more *_id programs. :)

> My udev persistent namimg implementation for EDD results in the example
> following tree:
> 
> $ tree /dev/disk/by-bios-id
> /dev/disk/by-bios-id/
> |-- int13_dev80 -> ../../sda
> |-- int13_dev80part1 -> ../../sda1
> |-- int13_dev80part2 -> ../../sda2
> |-- int13_dev80part5 -> ../../sda5
> |-- int13_dev80part6 -> ../../sda6
> |-- int13_dev81 -> ../../sdb
> |-- int13_dev81part1 -> ../../sdb1
> `-- int13_dev81part2 -> ../../sdb2

How about "by-firmware-id" to match the kernel sysfs name?
Or putting the links just in /dev/disk/by-id/* with an edd- prefix?

> To match the int13_dev8* device to the kernel block device, the
> "mbr_signature" for the device exposed by EDD must be matched to the
> disk signature read directly from the device by a user-space program
> (signature is 4-bytes long starting at offset 0x1B8 on the disk). To
> ensure that each disk can be matched to the corresponding BIOS disk,
> each disk should have a unique disk signature. In my current
> implementation with udev, I pass the kernel device (hd* or sd*) to a
> bash script which reads its signature and then tries to match it to a
> corresponding mbr_signature in the int13_dev* directories. If there is a
> unique match, it returns this directory to udev, and returns nothing
> otherwise. 
> 
> I have placed a rules file and the script that it calls here:
> http://linux.dell.com/files/edd/udev/, as well as a Python module that
> can be used to read and write the signatures. Please review my approach
> and let me know how I can improve this for eventual inclusion with udev.

The edd_id.sh should not check for a loaded module, otherwise it will not
work with compiled in EDD, right?
What is this -t option for? You need to pass an option to the program
and it just checks if the option equals "disk"?

I did a quick conversion to C. :) So we can use in in initramfs without
all the tools needed by the shell script. Please have a look at it...

Thanks,
Kay


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diff --git a/extras/edd_id/Makefile b/extras/edd_id/Makefile
new file mode 100644
--- /dev/null
+++ b/extras/edd_id/Makefile
@@ -0,0 +1,50 @@
+# Makefile for edd_id
+#
+# Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
+#
+# 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; version 2 of the License.
+#
+
+PROG = edd_id
+
+all:	$(PROG)
+
+prefix =
+exec_prefix =	${prefix}
+etcdir =	${prefix}/etc
+sbindir =	${exec_prefix}/sbin
+usrbindir =	${exec_prefix}/usr/bin
+usrsbindir =	${exec_prefix}/usr/sbin
+mandir =	${prefix}/usr/share/man
+devddir =	${etcdir}/dev.d/default
+configdir =	${etcdir}/udev/
+initdir = 	${etcdir}/init.d/
+srcdir = .
+
+INSTALL = /usr/bin/install -c
+INSTALL_PROGRAM = ${INSTALL}
+INSTALL_DATA  = ${INSTALL} -m 644
+INSTALL_SCRIPT = ${INSTALL_PROGRAM}
+
+OBJS = $(PROG).o $(LIBUDEV)
+
+$(OBJS): $(HEADERS)
+
+.c.o:
+	$(QUIET) $(CC) $(CFLAGS) -c -o $@ $<
+
+$(PROG): $(OBJS) $(HEADERS)
+	$(QUIET) $(LD) $(LDFLAGS) -o $(PROG) $(OBJS) $(LIB_OBJS)
+
+clean:
+	rm -f $(PROG) $(OBJS)
+
+spotless: clean
+
+install: all
+	$(INSTALL_PROGRAM) $(PROG) $(DESTDIR)$(sbindir)/$(PROG)
+
+uninstall:
+	- rm $(DESTDIR)$(sbindir)/$(PROG)
diff --git a/extras/edd_id/edd_id.c b/extras/edd_id/edd_id.c
new file mode 100644
--- /dev/null
+++ b/extras/edd_id/edd_id.c
@@ -0,0 +1,156 @@
+/*
+ * cdrom_id - naming of BIOS disk devices via EDD
+ *
+ * Copyright (C) 2005 John Hull <John_Hull@dell.com>
+ * Copyright (C) 2005 Kay Sievers <kay.sievers@vrfy.org>
+ *
+ *	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 version 2 of the License.
+ *
+ */
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE 1
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <ctype.h>
+#include <errno.h>
+#include <dirent.h>
+#include <stdint.h>
+
+#include "../../logging.h"
+#include "../../udev_utils.h"
+
+#ifdef USE_LOG
+void log_message(int priority, const char *format, ...)
+{
+	va_list args;
+	static int udev_log = -1;
+
+	if (udev_log == -1) {
+		const char *value;
+
+		value = getenv("UDEV_LOG");
+		if (value)
+			udev_log = log_priority(value);
+		else
+			udev_log = LOG_ERR;
+	}
+
+	if (priority > udev_log)
+		return;
+
+	va_start(args, format);
+	vsyslog(priority, format, args);
+	va_end(args);
+}
+#endif
+
+int main(int argc, char *argv[])
+{
+	const char *node = NULL;
+	int i;
+	int export = 0;
+	uint32_t disk_id;
+	struct dirent *dent;
+	int disk_fd;
+	int sysfs_fd;
+	DIR *dir = NULL;
+	int rc = 1;
+
+	logging_init("edd_id");
+
+	for (i = 1 ; i < argc; i++) {
+		char *arg = argv[i];
+
+		if (strcmp(arg, "--export") == 0) {
+			export = 1;
+		} else
+			node = arg;
+	}
+	if (!node) {
+		err("no node specified");
+		fprintf(stderr, "no node specified\n");
+		rc = 2;
+		goto exit;
+	}
+
+	dir = opendir("/sys/firmware/edd");
+	if (!dir) {
+		info("no kernel EDD support");
+		fprintf(stderr, "no kernel EDD support\n");
+		goto exit;
+	}
+
+	disk_fd = open(node, O_RDONLY);
+	if (disk_fd < 0) {
+		info("unable to open '%s'", node);
+		fprintf(stderr, "unable to open '%s'\n", node);
+		rc = 3;
+		goto closedir;
+	}
+
+	if (lseek(disk_fd, 440, SEEK_SET) < 0) {
+		info("'%s' seek to signature failed", node);
+		rc = 4;
+		goto close;
+	}
+
+	if (read(disk_fd, &disk_id, sizeof(disk_id)) != sizeof(disk_id)) {
+		info("'%s' read signature failed", node);
+		rc = 5;
+		goto close;
+	}
+	info("read id 0x%08x from '%s'", disk_id, node);
+
+	for (dent = readdir(dir); dent != NULL; dent = readdir(dir)) {
+		char file[PATH_SIZE];
+		char sysfs_id_buf[256];
+		uint32_t sysfs_id;
+		ssize_t size;
+
+		if (dent->d_name[0] == '.')
+			continue;
+
+		snprintf(file, sizeof(file), "/sys/firmware/edd/%s/mbr_signature", dent->d_name);
+		file[sizeof(file)-1] = '\0';
+
+		sysfs_fd = open(file, O_RDONLY);
+		if (sysfs_fd < 0) {
+			info("unable to open sysfs '%s'", file);
+			continue;
+		}
+
+		size = read(sysfs_fd, sysfs_id_buf, sizeof(sysfs_id_buf)-1);
+		close(sysfs_fd);
+		if (size < 0) {
+			info("read sysfs '%s' failed", file);
+			continue;
+		}
+		sysfs_id_buf[size] = '\0';
+		info("read '%s' from '%s'", sysfs_id_buf, file);
+
+		sysfs_id = strtoul(sysfs_id_buf, NULL, 16);
+		if (disk_id == sysfs_id) {
+			if (export)
+				printf("ID_EDD=%s\n", dent->d_name);
+			else
+				printf("%s\n", dent->d_name);
+			rc = 0;
+			break;
+		}
+	}
+
+close:
+	close(disk_fd);
+closedir:
+	closedir(dir);
+exit:
+	logging_close();
+	return rc;
+}
diff --git a/test/simple-build-check.sh b/test/simple-build-check.sh
--- a/test/simple-build-check.sh
+++ b/test/simple-build-check.sh
@@ -8,6 +8,7 @@ EXTRAS="\
 	extras/usb_id \
 	extras/dasd_id \
 	extras/cdrom_id \
+	extras/edd_id \
 	extras/floppy \
 	extras/run_directory \
 	extras/firmware"