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

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

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.

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