[PATCH v2 1/1] fastboot: fb_getvar: Add getvar_logical_blocksize for NXP mfgtool

[Angus Ainslie]

Hi Sean,

On 2021-12-30 08:21, Sean Anderson wrote:
> On 12/29/21 8:35 AM, Angus Ainslie wrote:
>> Hi Sean,
>> 
>> On 2021-12-28 08:59, Sean Anderson wrote:
>>> Hi Angus,
>>> 
>>>> NXP's mfgtool queies the mmc blocksize and splits a sparse image 
>>>> into
>>>> blocksize size pieces for the upload.
>>> 
>>> It's still not clear to me why this is necessary. fastboot (for 
>>> example)
>>> transfers in blocks of max-download-size. Using the actual block size
>>> seems like it would result in unnecessary overhead.
>>> 
>> 
>> The version of uuu that we are using requires the block-size for the 
>> sparse upload
>> 
>> https://source.puri.sm/Librem5/mfgtools/-/blob/pureos/amber/libuuu/fastboot.cpp#L501
>> 
>> It looks like the upstream version will default to 4096 if the 
>> block-size is not provided
>> 
>> https://github.com/NXPmicro/mfgtools/blob/5397913ad97db422c1d70f314dedff4cb7d976b9/libuuu/fastboot.cpp#L642
>> 
>> Instead of making assumptions about the block size wouldn't it be 
>> better to provide one if requested ?
> 
> The block size is for the sparse image. This determines the granularity
> of the sections of the image. For example, if the block size is 1K, 
> then
> all sizes will be multiples of 1K. So if you have a block with 1 byte 
> of
> data and 1023 bytes of 0 then the whole block will be transferred
> instead of being replaced with a fill block.
> 

Thanks for the explanation on how it works.

> However, the sparse file block size size completely orthogonal to
> the block size of the device being written to. The only thing it 
> affects
> is the efficiency of the sparse image. For example, I generate my 
> sparse
> files with a block size of 1M, because it is a nice convenient number.
> 

Ok so the way the NXP's uuu uses the blocksize is not correct. However 
the tool is already out there in the wild.

Can we add the block-size response to support that tool or will it be 
required that uuu needs to be upgraded to work with mainline u-boot ?

Thanks
Angus

> --Sean