Difference b/w xfer_len and len fields

[Ian Lepore]

On Sat, 2015-05-30 at 20:17 +0530, Pratik Singhal wrote:
> What do you mean by "driver-internal" variables ?
> 

I mean that it is used within the lowest-level hardware-controller
driver, and is not used in any communication between that lowest layer
and the mmc or mmcsd layers.

-- Ian

> On Sat, May 30, 2015 at 7:15 PM, Ian Lepore <ian at freebsd.org> wrote:
> 
> > On Sat, 2015-05-30 at 11:26 +0530, Pratik Singhal wrote:
> > > What is the difference b/w the xfer_len and the len fields in the struct
> > > mmc_data in file sys/dev/mmc/mmcreg.h  ?
> > >
> > > AFAIK , len is the length of the data present in mmc_data , what is
> > > xfer_len ?
> > >
> >
> > The xfer_len field has historically been unused, until recently.  When
> > the dwc mmc driver was added, it uses xfer_len as a driver-internal
> > variable to track how much of the overal work is done as the IO
> > proceeds.
> >
> > -- Ian
> >
> >
> 
>