[U-Boot] [PATCH v4 09/15] dm: Cast away the const-ness of the global_data pointer

[Marek Vasut]

On Friday, June 20, 2014 at 06:07:02 AM, Simon Glass wrote:
> Hi Marek,
> 
> On 17 June 2014 23:36, Simon Glass <sjg at chromium.org> wrote:
> > Hi Marek,
> > 
> > On 17 June 2014 16:42, Marek Vasut <marex at denx.de> wrote:
> >> On Thursday, June 12, 2014 at 05:26:50 AM, Simon Glass wrote:
> >>> Hi Marek,
> >>> 
> >>> On 8 June 2014 01:00, Marek Vasut <marex at denx.de> wrote:
> >>> > On Friday, June 06, 2014 at 09:13:26 PM, Simon Glass wrote:
> >>> >> In a very few cases we need to adjust the driver model root device,
> >>> >> such as when setting it up at initialisation. Add a macro to make
> >>> >> this easier.
> >>> >> 
> >>> >> Signed-off-by: Simon Glass <sjg at chromium.org>
> >>> >> ---
> >>> > 
> >>> > [...]
> >>> > 
> >>> >> -     ret = device_bind_by_name(NULL, &root_info, &gd->dm_root);
> >>> >> +     ret = device_bind_by_name(NULL, &root_info, &DM_ROOT());
> >>> > 
> >>> > [...]
> >>> > 
> >>> >> +/* Cast away any volatile pointer */
> >>> >> +#define DM_ROOT()            (((gd_t *)gd)->dm_root)
> >>> >> +#define DM_UCLASS_ROOT()             (((gd_t *)gd)->uclass_root)
> >>> > 
> >>> > Can you implement this "DM_ROOT()" macro as a function instead ? I
> >>> > believe that'd be much nicer , would have typechecking etc., usual
> >>> > stuff.
> >>> 
> >>> I had a look at this. I don't see how I can do it, but you might have
> >>> ideas.
> >>> 
> >>> In this function call I need to pass a pointer without its const bit.
> >>> I made it const since nothing should change the dm root except driver
> >>> model itself.
> >> 
> >> All right, I will just be doing a little guesswork here. Shall you not
> >> have some functions to change the DM root then instead of exposing the
> >> DM root ? Such functions shall not be exported publicly , but available
> >> via separate header file too ?
> > 
> > Firstly I should retitle the commit - it is of course the volatile
> > that I'm trying to get rid of as it says in the commit message. I
> > might have just been trying to confuse everyone.
> > 
> > I have code like this:
> > 
> > INIT_LIST_HEAD(&gd->uclass_root);
> > 
> > I don't see how I can turn this into a function. I suppose I could
> > init the list head in a temporary variable and then assign it to
> > gd->uclass_root, perhaps with memcpy(), but that doesn't really seem
> > any better to me.
> > 
> >> Sorry, I might be completely wrong.
> > 
> > Well I'm not saying it's pretty, so if you have time and come up with
> > a better option please let me know.
> > 
> > Also, this is not exported 'publicly'. It is in device-internal.h
> 
> Please let me know on this one. If you have a better option please let me
> know.
> 
> Otherwise I'd like to do a dm pull request soon to get these fixes
> into the release.

Ah, please get the PR out. We can tweak this later I'm sure. Apologies for 
holding you and the PR.