[PATCH 09/15] blk: blkmap: Support mapping to device of any block size

[Tobias Waldekranz]

On tis, sep 26, 2023 at 16:43, Bin Meng <bmeng at tinylab.org> wrote:
> At present if a device to map has a block size other than 512,
> the blkmap map process just fails. There is no reason why we
> can't just use the block size of the mapped device.

Won't this be very confusing to the user?

The blkmap device uses a fixed block size of 512:

https://source.denx.de/u-boot/u-boot/-/blob/master/drivers/block/blkmap.c?ref_type=heads#L393

So if I map a slice of a 4k device into a blkmap, then

    blkmap read 0x80000000 0 1

would copy 4k instead of 512 bytes from the lower device to 0x80000000,
even though the blkmap reports a block size of 512.

It seems to me that the expected behavior would be that only the first
512 bytes would be copied in the command above.

>
> Signed-off-by: Bin Meng <bmeng at tinylab.org>
> ---
>
>  drivers/block/blkmap.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/block/blkmap.c b/drivers/block/blkmap.c
> index f6acfa8927..149a4cac3e 100644
> --- a/drivers/block/blkmap.c
> +++ b/drivers/block/blkmap.c
> @@ -171,11 +171,11 @@ int blkmap_map_linear(struct udevice *dev, lbaint_t blknr, lbaint_t blkcnt,
>  
>  	bd = dev_get_uclass_plat(bm->blk);
>  	lbd = dev_get_uclass_plat(lblk);
> -	if (lbd->blksz != bd->blksz)
> -		/* We could support block size translation, but we
> -		 * don't yet.
> -		 */

Hence this comment ^

> -		return -EINVAL;
> +	if (lbd->blksz != bd->blksz) {
> +		/* update to match the mapped device */
> +		bd->blksz = lbd->blksz;
> +		bd->log2blksz = LOG2(bd->blksz);
> +	}
>  
>  	linear = malloc(sizeof(*linear));
>  	if (!linear)
> -- 
> 2.25.1