[U-Boot,2/2] disk: default to HW partition 0 if not specified

From: Stephen Warren <swarren@nvidia.com>

Currently, get_device()/get_dev_hwpart() for MMC devices does not select
an explicit HW partition unless the user explicitly requests one, i.e. by
requesting device "mmc 0.0" rather than just "mmc 0". I think it makes
more sense if the default is to select HW partition 0 (main data area)
if the user didn't request a specific partition. Otherwise, the following
happens, which feels wrong:

Select HW partition 1 (boot0):
mmc dev 0 1

Attempts to access SW partition 1 on HW partition 1 (boot0), rather than
SW partition 1 on HW partition 0 (main data area):
ls mmc 0:1 /

With this patch, the second command above re-selects the main data area.

Many device types don't support HW partitions at all, so if HW partition
0 is selected (either explicitly or as the default) and there's no
select_hwpart function, we simply skip attempting to select a HW
partition.

Some MMC devices (i.e. SD cards) don't support HW partitions. However,
this patch still works, since mmc_start_init() sets the current
partition number to 0, and mmc_select_hwpart() succeeds if the requested
partition is already selected.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
---
 disk/part.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Hi Stephen,

On May 23, 2014, at 9:48 PM, Stephen Warren wrote:

> From: Stephen Warren <swarren@nvidia.com>
> 
> Currently, get_device()/get_dev_hwpart() for MMC devices does not select
> an explicit HW partition unless the user explicitly requests one, i.e. by
> requesting device "mmc 0.0" rather than just "mmc 0". I think it makes
> more sense if the default is to select HW partition 0 (main data area)
> if the user didn't request a specific partition. Otherwise, the following
> happens, which feels wrong:
> 
> Select HW partition 1 (boot0):
> mmc dev 0 1
> 
> Attempts to access SW partition 1 on HW partition 1 (boot0), rather than
> SW partition 1 on HW partition 0 (main data area):
> ls mmc 0:1 /
> 
> With this patch, the second command above re-selects the main data area.
> 
> Many device types don't support HW partitions at all, so if HW partition
> 0 is selected (either explicitly or as the default) and there's no
> select_hwpart function, we simply skip attempting to select a HW
> partition.
> 
> Some MMC devices (i.e. SD cards) don't support HW partitions. However,
> this patch still works, since mmc_start_init() sets the current
> partition number to 0, and mmc_select_hwpart() succeeds if the requested
> partition is already selected.
> 
> Signed-off-by: Stephen Warren <swarren@nvidia.com>
> ---
> disk/part.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/disk/part.c b/disk/part.c
> index 2827089d8d5f..b3097e32f0eb 100644
> --- a/disk/part.c
> +++ b/disk/part.c
> @@ -86,7 +86,7 @@ block_dev_desc_t *get_dev_hwpart(const char *ifname, int dev, int hwpart)
> 			block_dev_desc_t *dev_desc = reloc_get_dev(dev);
> 			if (!dev_desc)
> 				return NULL;
> -			if (hwpart == -1)
> +			if (hwpart == 0 && !select_hwpart)
> 				return dev_desc;
> 			if (!select_hwpart)
> 				return NULL;
> @@ -102,7 +102,7 @@ block_dev_desc_t *get_dev_hwpart(const char *ifname, int dev, int hwpart)
> 
> block_dev_desc_t *get_dev(const char *ifname, int dev)
> {
> -	return get_dev_hwpart(ifname, dev, -1);
> +	return get_dev_hwpart(ifname, dev, 0);
> }
> #else
> block_dev_desc_t *get_dev_hwpart(const char *ifname, int dev, int hwpart)
> @@ -460,7 +460,7 @@ int get_device(const char *ifname, const char *dev_hwpart_str,
> 		hwpart_str++;
> 	} else {
> 		dev_str = dev_hwpart_str;
> -		hwpart = -1;
> +		hwpart = 0;
> 	}
> 
> 	dev = simple_strtoul(dev_str, &ep, 16);
> -- 
> 1.8.1.5

Same comment for part 1, slight behavioral change but with no known side-effects.

Thanks, applied.

-- Pantelis

Acked-by: Pantelis Antoniou <panto@antoniou-consulting.com>