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Commit d39de28c authored by Ben Hutchings's avatar Ben Hutchings Committed by Linus Torvalds
Browse files

dmi_scan: add comments on dmi_present() and the loop in dmi_scan_machine() 



My previous refactoring in commit 79bae42d ("dmi_scan: refactor
dmi_scan_machine(), {smbios,dmi}_present()") resulted in slightly tricky
code (though I think it's more elegant).  Explain what it's doing.

Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
Cc: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Cc: Jean Delvare <jdelvare@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 62c61046

drivers/firmware/dmi_scan.c

+14 −0
Original line number Diff line number Diff line
@@ -419,6 +419,13 @@ static void __init dmi_format_ids(char *buf, size_t len) 
			    dmi_get_system_info(DMI_BIOS_DATE));

}



/*

 * Check for DMI/SMBIOS headers in the system firmware image.  Any

 * SMBIOS header must start 16 bytes before the DMI header, so take a

 * 32 byte buffer and check for DMI at offset 16 and SMBIOS at offset

 * 0.  If the DMI header is present, set dmi_ver accordingly (SMBIOS

 * takes precedence) and return 0.  Otherwise return 1.

 */

static int __init dmi_present(const u8 *buf)

{

	int smbios_ver;
@@ -506,6 +513,13 @@ void __init dmi_scan_machine(void) 
		if (p == NULL)

			goto error;



		/*

		 * Iterate over all possible DMI header addresses q.

		 * Maintain the 32 bytes around q in buf.  On the

		 * first iteration, substitute zero for the

		 * out-of-range bytes so there is no chance of falsely

		 * detecting an SMBIOS header.

		 */

		memset(buf, 0, 16);

		for (q = p; q < p + 0x10000; q += 16) {

			memcpy_fromio(buf + 16, q, 16);