[M] Change in flashrom[main]: dmi: Scan in sysfs first

[Patrick Rudolph (Code Review)]

Attention is currently required from: Patrick Rudolph.

Hello Patrick Rudolph,

I'd like you to do a code review.
Please visit

https://review.coreboot.org/c/flashrom/+/78302?usp=email

to review the following change.

Change subject: dmi: Scan in sysfs first
......................................................................

dmi: Scan in sysfs first

When not running on Windows scan the sysfs for DMI table 3 first.
This is faster and less intrusive than accessing the memory directly.

Needs tests on internal programmer.

Change-Id: I0d0f461b64a6f6ed6c1a3a62d759b9c395ad0ec8
Signed-off-by: Patrick Rudolph 
---
M dmi.c
1 file changed, 51 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/flashrom refs/changes/02/78302/1

diff --git a/dmi.c b/dmi.c
index 94e47fb..5a50705 100644
--- a/dmi.c
+++ b/dmi.c
@@ -30,6 +30,10 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <errno.h>
+#if !IS_WINDOWS
+#include <sys/stat.h>
+#endif

#include "flash.h"
 #include "hwaccess_physmap.h"
@@ -41,6 +45,8 @@
 /* Strings longer than 4096 in DMI are just insane. */
 #define DMI_MAX_ANSWER_LEN 4096

+#define LINUX_DMI_SYSFS_TABLE_3		"/sys/firmware/dmi/entries/3-0/raw"
+
 static bool g_has_dmi_support = false;

bool dmi_is_supported(void)
@@ -232,6 +238,45 @@
    physunmap(dmi_table_mem, len);
 }

+
+#if !IS_WINDOWS
+/* read the chassis type from a sysfs file */
+static int dmi_sysfs(int *is_laptop)
+{
+	size_t bytes_read;
+	uint8_t buf[6];
+	struct stat s;
+	FILE *fp;
+
+	msg_pdbg("Using sysfs DMI decoder.\n");
+
+	if (stat(LINUX_DMI_SYSFS_TABLE_3, &s) < 0) {
+		msg_pdbg("Cannot stat "%s": %s\n", LINUX_DMI_SYSFS_TABLE_3,
+			 strerror(errno));
+		return 1;
+	}
+
+	if ((fp = fopen(LINUX_DMI_SYSFS_TABLE_3, "r")) == NULL) {
+		msg_perr("Cannot open %s\n", LINUX_DMI_SYSFS_TABLE_3);
+		return 1;
+	}
+
+	clearerr(fp);
+	bytes_read = fread(buf, 1, sizeof(buf), fp);
+	if (feof(fp) || ferror(fp) || bytes_read < sizeof(buf)) {
+		msg_perr("Error occurred when reading %s\n",
+			 LINUX_DMI_SYSFS_TABLE_3);
+		fclose(fp);
+		return 1;
+	}
+	fclose(fp);
+
+	*is_laptop = dmi_chassis_type(buf[5]);
+
+	return 0;
+}
+#endif
+
 #if SM_SUPPORT
 static int smbios_decode(uint8_t *buf, int *is_laptop)
 {
@@ -400,6 +445,12 @@
    	return;
    }

+#if !IS_WINDOWS
+	/* Try to read sysfs first */
+	if (!dmi_sysfs(is_laptop))
+		return;
+#endif
+
    /* dmi_fill fills the dmi_strings array, and if possible set the is_laptop parameter. */
    if (dmi_fill(is_laptop) != 0)
    	return;