When creating images targeted for SD cards, generating partitions on
cylinder boundaries makes no sense, because cylinders heads and sectors
have no meaning on this linear storage media. What does have meaning are
erase block boundaries, and partitions, especially FAT partitions,
should start on erase block boundaries.
Reference:
https://lwn.net/Articles/428584/
https://wiki.linaro.org/WorkingGroups/Kernel/Projects/FlashCardSurvey
The attached patch adds a -l (for aLign) option to ptgen to allow it to
generate size-aligned partition starts rather than rounding to cylinder
boundaries. Example usage, for the recommended generic case of 4MB
erase block SD cards:
ptgen -o ${OUTPUT} -h 255 -s 63 -l 4096 -t c -p ${BOOTSIZE}
--- tools/firmware-utils/src/ptgen.c.orig 2012-08-02 16:42:13.528342554
-0400
+++ tools/firmware-utils/src/ptgen.c 2012-08-03 11:39:39.592992950 -0400
@@ -56,6 +56,7 @@
int active = 1;
int heads = -1;
int sectors = -1;
+int kb_align = 0;
struct partinfo parts[4];
char *filename = NULL;
@@ -117,6 +118,11 @@
return sect + cyl_size - (sect % cyl_size);
}
+/* round the sector number up to the kb_align boundary */
+static inline unsigned long round_to_kb(long sect) {
+ return ((sect - 1) / kb_align + 1) * kb_align;
+}
+
/* check the partition sizes and write the partition table */
static int gen_ptable(int nr)
{
@@ -132,8 +138,13 @@
}
pte[i].active = ((i + 1) == active) ? 0x80 : 0;
pte[i].type = parts[i].type;
- pte[i].start = cpu_to_le16(start = sect + sectors);
- sect = round_to_cyl(start + parts[i].size * 2);
+ start = sect + sectors;
+ if (kb_align != 0)
+ start = round_to_kb(start);
+ pte[i].start = cpu_to_le16(start);
+ sect = start + parts[i].size * 2;
+ if (kb_align == 0)
+ sect = round_to_cyl(sect);
pte[i].length = cpu_to_le16(len = sect - start);
to_chs(start, pte[i].chs_start);
to_chs(start + len - 1, pte[i].chs_end);
@@ -167,7 +178,7 @@
static void usage(char *prog)
{
- fprintf(stderr, "Usage: %s [-v] -h <heads> -s <sectors> -o <outputfile>
[-a 0..4] [[-t <type>] -p <size>...] \n", prog);
+ fprintf(stderr, "Usage: %s [-v] -h <heads> -s <sectors> -o <outputfile>
[-a 0..4] [-l <align kB>] [[-t <type>] -p <size>...] \n", prog);
exit(1);
}
@@ -177,7 +188,7 @@
int ch;
int part = 0;
- while ((ch = getopt(argc, argv, "h:s:p:a:t:o:v")) != -1) {
+ while ((ch = getopt(argc, argv, "h:s:p:a:t:o:vl:")) != -1) {
switch (ch) {
case 'o':
filename = optarg;
@@ -207,6 +218,9 @@
if ((active < 0) || (active > 4))
active = 0;
break;
+ case 'l':
+ kb_align = (int) strtoul(optarg, NULL, 0) * 2;
+ break;
case '?':
default:
usage(argv[0]);
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