[U-Boot] [PATCH] dm: video: fix abuse of enum

[Lothar Waßmann]

Hi,

On Thu, 6 Jul 2017 12:22:52 +0000 Marcel Ziswiler wrote:
> Dear Lothar
> 
> On Thu, 2017-07-06 at 09:50 +0200, Lothar Waßmann wrote:
> > Hi,
> > 
> > On Wed, 5 Jul 2017 22:49:28 -0600 Simon Glass wrote:
> > > Hi Lothar,
> > > 
> > > On 23 June 2017 at 00:30, Lothar Waßmann <LW at karo-electronics.de>
> > > wrote:
> > > > Hi,
> > > > 
> > > > On Wed, 21 Jun 2017 09:59:05 +0200 Lothar Waßmann wrote:
> > > > > Hi,
> > > > > 
> > > > > On Tue, 20 Jun 2017 12:26:29 -0600 Simon Glass wrote:
> > > > > > Hi Lothar,
> > > > > > 
> > > > > > On 20 June 2017 at 04:25, Lothar Waßmann <LW at karo-electronics
> > > > > > .de> wrote:
> > > > > > > LCD_MAX_WIDTH, LCD_MAX_HEIGHT and LCD_MAX_LSBPP are not
> > > > > > > alternative
> > > > > > > values for one specific variable, but unrelated entities
> > > > > > > with distinct
> > > > > > > purposes. There is no use defining them as values of an
> > > > > > > 'enum'.
> > > > > > 
> > > > > > Can you explain why #define is better? I prefer enum since
> > > > > > they are a
> > > > > > compiler construct instead of preprocessor (thus no need for
> > > > > > brackets,
> > > > > > no strange conversion things) and the debugger knows about
> > > > > > them.
> > > > > > 
> > > > > 
> > > > > An enum defines alternative values for one specific entity
> > > > > (e.g.
> > > > > clauses for a switch construct), but not a collection of
> > > > > arbitrary data
> > > > > items.
> > > > > 
> > > > > > > The 'enum' construct would fail miserably for an LCD
> > > > > > > controller that
> > > > > > > has a square max. frame size (e.g. 4096x4096).
> > > > > > 
> > > > > > What does this mean? I don't understand sorry.
> > > > > > 
> > > > > 
> > > > > Try your enum with MAX_LCD_WITDH == MAC_LCD_HEIGHT.
> > > 
> > > Can you please be explicit as to what the problem is? Sorry but I
> > > don't understand what you are driving at. Do you have a test
> > > program
> > > which shows the problem?
> > > 
> > 
> > You cannot have two different enum items with the same value!
> > Thus:
> > enum {
> > 	MAX_LCD_WIDTH = 4096,
> > 	MAX_LCD_HEIGHT = 4096,
> > };
> > won't compile.
> 
> Says who?
> 
> At least my gcc compilers even compile the following just fine:
> 
> enum {
> 	MAX_LCD_WIDTH = 4096,
> 	MAX_LCD_HEIGHT = MAX_LCD_WIDTH,
> };
>
Sorry, I was so locked in to the "normal" use of enum that I got
confused.


Lothar Waßmann