On Mon, 2024-10-21 at 12:58 +0200, Thomas Zimmermann wrote:
> Hi
>
> Am 21.10.24 um 12:08 schrieb Arnd Bergmann:
> > On Mon, Oct 21, 2024, at 07:52, Thomas Zimmermann wrote:
> > > Am 08.10.24 um 14:39 schrieb Niklas Schnelle:
> > d 100644
> > > > --- a/drivers/gpu/drm/qxl/Kconfig
> > > > +++ b/drivers/gpu/drm/qxl/Kconfig
> > > > @@ -2,6 +2,7 @@
> > > > config DRM_QXL
> > > > tristate "QXL virtual GPU"
> > > > depends on DRM && PCI && MMU
> > > > + depends on HAS_IOPORT
> > > Is there a difference between this style (multiple 'depends on') and the
> > > one used for gma500 (&& && &&)?
> > No, it's the same. Doing it in one line is mainly useful
> > if you have some '||' as well.
> >
> > > > @@ -105,7 +106,9 @@ static void bochs_vga_writeb(struct bochs_device *bochs, u16 ioport, u8 val)
> > > >
> > > > writeb(val, bochs->mmio + offset);
> > > > } else {
> > > > +#ifdef CONFIG_HAS_IOPORT
> > > > outb(val, ioport);
> > > > +#endif
> > > Could you provide empty defines for the out() interfaces at the top of
> > > the file?
> > That no longer works since there are now __compiletime_error()
> > versions of these funcitons. However we can do it more nicely like:
> >
> > diff --git a/drivers/gpu/drm/tiny/bochs.c b/drivers/gpu/drm/tiny/bochs.c
> > index 9b337f948434..034af6e32200 100644
> > --- a/drivers/gpu/drm/tiny/bochs.c
> > +++ b/drivers/gpu/drm/tiny/bochs.c
> > @@ -112,14 +112,12 @@ static void bochs_vga_writeb(struct bochs_device *bochs, u16 ioport, u8 val)
> > if (WARN_ON(ioport < 0x3c0 || ioport > 0x3df))
> > return;
> >
> > - if (bochs->mmio) {
> > + if (!IS_DEFINED(CONFIG_HAS_IOPORT) || bochs->mmio) {
> > int offset = ioport - 0x3c0 + 0x400;
> >
> > writeb(val, bochs->mmio + offset);
> > } else {
> > -#ifdef CONFIG_HAS_IOPORT
> > outb(val, ioport);
> > -#endif
> > }
>
> For all functions with such a pattern, could we use:
>
> bool bochs_uses_mmio(bochs)
> {
> return !IS_DEFINED(CONFIG_HAS_IOPORT) || bochs->mmio
> }
>
> void writeb_func()
> {
> if (bochs_uses_mmio()) {
> writeb()
> #if CONFIG_HAS_IOPORT
> } else {
> outb()
> #endif
> }
> }
>
I think if the helper were __always_inline we could still take
advantage of the dead code elimination and combine this with Arnd's
approach. Though I feel like it is a bit odd to try to do the MMIO
approach despite bochs->mmio being false on !HAS_IOPORT systems.
Is that what you wanted to correct by keeping the #ifdef
CONFIG_HAS_IOPORT around the else? And yes the warning makes sense to
me too.
Thanks,
Niklas
