linux-kernel - [PATCH RFC] dmi-scan: Use little-endian for the first 3 fields of the UUID.

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Message-ID: <20110119185411.49668f81@destiny.ordissimo>
Date:	Wed, 19 Jan 2011 18:54:11 +0100
From:	Anisse Astier <anisse@...ier.eu>
To:	linux-kernel@...r.kernel.org
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Pascal VITOUX <pascal@...stantiel.fr>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Jean Delvare <khali@...ux-fr.org>
Subject: [PATCH RFC] dmi-scan: Use little-endian for the first 3 fields of
 the UUID.


From: Pascal VITOUX <pascal@...stantiel.fr>

 - Get SMBIOS version.
 - Byte-swap the first 3 fields of the UUID (DMI type 1) as off SMBIOS
   version 2.6.

This patch is an adaptation of Jean Delvare patches for dmidecode
rev1.100, rev1.01 and rev1.119.
http://cvs.savannah.gnu.org/viewvc/dmidecode/dmidecode.c?root=dmidecode&view=log

It is intended to get the same uuid from dmidecode tool as from sysfs kernel
tree, more compliant with SMBIOS specification.
Therefore this patch will have the kernel return a different UUID if you
are using a recent BIOS implementing SMBIOS >= 2.6.

Signed-off-by: Pascal VITOUX <pascal@...stantiel.fr>
Signed-off-by: Anisse Astier <anisse@...ier.eu>
---
Hi,

I'd like to get some feedback on this patch. It doesn't modify the
API/ABI, but modifies the value returned by kernel on a given hardware,
so it could potentially break a (very) badly written app.

Disclaimer: Although I've applied my Signed-off-by, Pascal and I work for
the same company.

Regards,
Anisse

---
 drivers/firmware/dmi_scan.c |   36 ++++++++++++++++++++++++++++++++++--
 1 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index e28e41668..b6278a7 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -99,6 +99,7 @@ static void dmi_table(u8 *buf, int len, int num,
 static u32 dmi_base;
 static u16 dmi_len;
 static u16 dmi_num;
+static u16 dmi_ver;
 
 static int __init dmi_walk_early(void (*decode)(const struct dmi_header *,
 		void *))
@@ -169,7 +170,18 @@ static void __init dmi_save_uuid(const struct dmi_header *dm, int slot, int inde
 	if (!s)
 		return;
 
-	sprintf(s, "%pUB", d);
+	/*
+	 * As off version 2.6 of the SMBIOS specification, the first 3
+	 * fields of the UUID are supposed to be encoded on little-endian.
+	 * The specification says that this is the defacto standard,
+	 * however I've seen systems following RFC 4122 instead and use
+	 * network byte order, so I am reluctant to apply the byte-swapping
+	 * for older versions.
+	 */
+	if (dmi_ver >= 0x0206)
+		sprintf(s, "%pUL", d);
+	else
+		sprintf(s, "%pUB", d);
 
         dmi_ident[slot] = s;
 }
@@ -400,9 +412,29 @@ static int __init dmi_present(const char __iomem *p)
 		dmi_base = (buf[11] << 24) | (buf[10] << 16) |
 			(buf[9] << 8) | buf[8];
 
+		/* SMBIOS version */
+		dmi_ver = (*(u8 *)(p - 0x10 + 0x06) << 8) +
+			*(u8 *)(p - 0x10 + 0x07);
+
+		/* Some BIOS report weird SMBIOS version, fix that up */
+		switch (dmi_ver) {
+		case 0x021F:
+			printk(KERN_INFO "SMBIOS version fixup (2.%d -> 2.%d).\n",
+			       31, 3);
+			dmi_ver = 0x0203;
+			break;
+		case 0x0233:
+			printk(KERN_INFO "SMBIOS version fixup (2.%d -> 2.%d).\n",
+			       51, 6);
+			dmi_ver = 0x0206;
+			break;
+		}
+		printk(KERN_INFO "SMBIOS version %d.%d.\n", dmi_ver >> 8,
+		       dmi_ver & 0xFF);
+
 		/*
 		 * DMI version 0.0 means that the real version is taken from
-		 * the SMBIOS version, which we don't know at this point.
+		 * the SMBIOS version.
 		 */
 		if (buf[14] != 0)
 			printk(KERN_INFO "DMI %d.%d present.\n",
-- 
1.7.3.2

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