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

[Jörn Engel]

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

-- 
Public Domain  - Free as in Beer
General Public - Free as in Speech
BSD License    - Free as in Enterprise
Shared Source  - Free as in "Work will make you..."