[U-Boot] [RFC PATCH] cmd: gpt: add - partition size parsing

[Julian Scheel]

Hi Michael,

On 08.06.2016 10:18, Michael Trimarchi wrote:
> This patch try to parse name=userdata,size=-,uuid=${uuid_gpt_userdata};
>
> gpt mmc write 0 $partitions
> gpt mmc verify 0 $partitions
>
> Signed-off-by: Michael Trimarchi <michael at amarulasolutions.com>
> ---
>  cmd/gpt.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/cmd/gpt.c b/cmd/gpt.c
> index 8ffaef3..3d9706b 100644
> --- a/cmd/gpt.c
> +++ b/cmd/gpt.c
> @@ -181,6 +181,7 @@ static int set_gpt_info(struct blk_desc *dev_desc,
>  	disk_partition_t *parts;
>  	int errno = 0;
>  	uint64_t size_ll, start_ll;
> +	lbaint_t offset = 0;
>
>  	debug("%s:  lba num: 0x%x %d\n", __func__,
>  	      (unsigned int)dev_desc->lba, (unsigned int)dev_desc->lba);
> @@ -296,8 +297,14 @@ static int set_gpt_info(struct blk_desc *dev_desc,
>  		}
>  		if (extract_env(val, &p))
>  			p = val;
> -		size_ll = ustrtoull(p, &p, 0);
> -		parts[i].size = lldiv(size_ll, dev_desc->blksz);
> +		if ((strcmp(p, "-") == 0)) {
> +			/* remove first usable lba and last block */
> +			parts[i].size = dev_desc->lba - 34  - 1 - offset;

Looking into part_efi.c the last_usable block is dev_desc->lba - 34 and 
the first usable block is 34. So 34 needs to be substracted twice, 
otherwise you hit the "Partitions layout exceds disk size" error case in 
part_efi.c

> +		} else {
> +			size_ll = ustrtoull(p, &p, 0);
> +			parts[i].size = lldiv(size_ll, dev_desc->blksz);
> +		}
> +
>  		free(val);
>
>  		/* start address */
> @@ -310,6 +317,8 @@ static int set_gpt_info(struct blk_desc *dev_desc,
>  			free(val);
>  		}
>
> +		offset += parts[i].size + parts[i].start;

This appears to be wrong. We have two cases here:

a) start is not specified for parition i
In this case the code works as parts[i].start is 0 and size accumulates 
to the proper offsets

b) start is specified for a partition i, example table:

part[0].size = 10

part[1].size = 10
part[1].start = 10

part[2].size = 10

This table should end up in the same table as if part[1].start = 10 
would have been omited. In fact it will lead to:
part[0] = 0-10
part[1] = 10-20
part[2] = 30-40

So it introduced a gap, because start is assumed to be relative to 
previous offset, which is not the case.

I think the proper handling would be:
if (parts[i].start)
     offset = parts[i].size + parts[i].start;
else
     offset += parts[i].size;

> +
>  		/* bootable */
>  		if (found_key(tok, "bootable"))
>  			parts[i].bootable = 1;
>

While preparing a patch to fix the previously mentioned issues, so that 
gpt writing becomes usable again, I started to wonder why you added this 
patch at all. In fact the usecase you describe in the commit message did 
work perfectly without this patch, because part_efi.c automatically 
scales a partition without given size to the available space, in case it 
is the last partition. (See: 
http://git.denx.de/?p=u-boot.git;a=blob;f=disk/part_efi.c;h=01f71bee79e2656a295ee1cd3505185efc9c5cf7;hb=HEAD#l447)
So imho this patch should simply be reverted or did I miss something 
important?

Regards,
Julian