Hi Florian,
Gentle ping ?
On Sunday 20 November 2011 11:55:22 Laurent Pinchart wrote:
> On Sunday 20 November 2011 03:00:33 Florian Tobias Schandinat wrote:
> > Hi Laurent,
> >
> > On 08/31/2011 11:18 AM, Laurent Pinchart wrote:
> > > This API will be used to support YUV frame buffer formats in a standard
> > > way.
> >
> > looks like the union is causing problems. With this patch applied I get
> >
> > errors like this:
> > CC [M] drivers/auxdisplay/cfag12864bfb.o
> >
> > drivers/auxdisplay/cfag12864bfb.c:57: error: unknown field ‘red’
> > specified in initializer
>
> *ouch*
>
> gcc < 4.6 chokes on anonymous unions initializers :-/
>
> [snip]
>
> > > @@ -246,12 +251,23 @@ struct fb_var_screeninfo {
> > >
> > > __u32 yoffset; /* resolution */
> > >
> > > __u32 bits_per_pixel; /* guess what */
> > >
> > > - __u32 grayscale; /* != 0 Graylevels instead of colors */
> > >
> > > - struct fb_bitfield red; /* bitfield in fb mem if true color, */
> > > - struct fb_bitfield green; /* else only length is significant */
> > > - struct fb_bitfield blue;
> > > - struct fb_bitfield transp; /* transparency */
> > > + union {
> > > + struct { /* Legacy format API */
> > > + __u32 grayscale; /* 0 = color, 1 = grayscale */
> > > + /* bitfields in fb mem if true color, else only */
> > > + /* length is significant */
> > > + struct fb_bitfield red;
> > > + struct fb_bitfield green;
> > > + struct fb_bitfield blue;
> > > + struct fb_bitfield transp; /* transparency */
> > > + };
> > > + struct { /* FOURCC-based format API */
> > > + __u32 fourcc; /* FOURCC format */
> > > + __u32 colorspace;
> > > + __u32 reserved[11];
> > > + } fourcc;
> > > + };
>
> We can't name the union, otherwise this will change the userspace API.
>
> We could "fix" the problem on the kernel side with
>
> #ifdef __KERNEL__
> } color;
> #else
> };
> #endif
(and the structure that contains the grayscale, red, green, blue and transp
fields would need to be similarly named, the "rgb" name comes to mind)
> That's quite hackish though... What's your opinion ?
>
> It would also not handle userspace code that initializes an
> fb_var_screeninfo structure with named initializers, but that shouldn't
> happen, as application should read fb_var_screeninfo , modify it and write
> it back.
>
> > > __u32 nonstd; /* != 0 Non standard pixel format */
--
Regards,
Laurent Pinchart
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