Re: [PATCH] fix for mtd partitions for erase_size != 2^X

Jörn Engel
2005-09-25T13:16:34Z

On Fri, 23 September 2005 20:02:42 +0200, Peter Menzebach wrote:
>
> Here a trivial patch,
> which allows correct creation of mtd partitions, which have erase sizes
> which are not a power of 2.
>
> Best regards
> Peter
>
> Sorry, I didn't succeed to get the patch accepted by the mailing list as
> attachment.

I actually prefer inline. Except that your mailer seems to have
messed things up - grr.

> --- drivers/mtd/mtdpart.c.orig 2005-09-23 09:28:07.000000000 +0200
> +++ drivers/mtd/mtdpart.c 2005-09-23 09:29:37.000000000 +0200
> @@ -465,9 +465,9 @@
> if (slave->offset == MTDPART_OFS_APPEND)
> slave->offset = cur_offset;
> if (slave->offset == MTDPART_OFS_NXTBLK) {
> - u_int32_t emask = master->erasesize-1;
> - slave->offset = (cur_offset + emask) & ~emask;
> - if (slave->offset != cur_offset) {
> + slave->offset = cur_offset;
> + if ((cur_offset % master->erasesize) != 0) {
> + slave->offset = ((cur_offset / master->erasesize) + 1)
> * master->erasesize;
> printk(KERN_NOTICE "Moving partition %d: "
> "0x%08x -> 0x%08x\n", i,
> cur_offset, slave->offset);

Looks complicated. I guess we could use the equivalent of this:
#define ALIGN(x,a) (((x)+(a)-1)&~((a)-1))
in some header. Then your patch would be as simple as

if (slave->offset == MTDPART_OFS_APPEND)
slave->offset = cur_offset;
if (slave->offset == MTDPART_OFS_NXTBLK) {
- u_int32_t emask = master->erasesize-1;
- slave->offset = (cur_offset + emask) & ~emask;
+ slave->offset = TRUE_ALIGN(cur_offset, master->erasesize);
if (slave->offset != cur_offset) {
printk(KERN_NOTICE "Moving partition %d: "
"0x%08x -> 0x%08x\n", i,

Maybe this:
#define TRUE_ALIGN(x,a) (((x)+(a)-1) - ((x)+(a)-1) % a)

The macro is still complicated, but we just have to get it right once.

Jörn

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