[U-Boot] [PATCH] FIX: fat: Provide correct return code from disk_{read|write} to upper layers

[Lukasz Majewski <l.majewski@samsung.com>]

Hi Lukasz,

> Hi Tom,
> 
> > On Thu, Sep 03, 2015 at 02:21:39PM +0200, Lukasz Majewski wrote:
> > 
> > > It is very common that FAT code is using following pattern:
> > > if (disk_{read|write}() < 0)
> > >         return -1;
> > > 
> > > Up till now the above code was dead, since disk_{read|write) could
> > > only return value >= 0.
> > > As a result some errors from medium layer (i.e. eMMC/SD) were not
> > > caught.
> > > 
> > > The above behavior was caused by block_{read|write|erase} declared
> > > at struct block_dev_desc (@part.h). It returns unsigned long,
> > > where 0 indicates error and > 0 indicates that medium operation
> > > was correct.
> > > 
> > > This patch as error regards 0 returned from
> > > block_{read|write|erase} when nr_blocks is grater than zero.
> > > Read/Write operation with nr_blocks=0 should return 0 and hence
> > > is not considered as an error.
> > > 
> > > Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
> > > 
> > > Test HW: Odroid XU3 - Exynos 5433
> > 
> > Can you pick up Stephen's FAT replacement series and see if it also
> > fixes this problem?  Thanks!
> > 
> 
> Ok, I will test this fat implementation.

I've applied v2 of this patchset
on top of SHA1: 79c884d7e449a63fa8f07b7495f8f9873355c48f

Unfortunately, DFU tests fail with first attempt to pass the test.

Apparently this code needs some more review/testing before being
included to main line.

> 
> However, since for v2015.10 it won't be included, I would also opt for
> adding this fix to the current u-boot.
> 



-- 
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group