On Wed, Nov 29, 2017 at 04:40:18PM +0100, Christian König wrote:
> Am 29.11.2017 um 16:36 schrieb Sean Paul:
> > On Wed, Nov 29, 2017 at 04:24:21PM +0100, Christian König wrote:
> > > Am 29.11.2017 um 16:20 schrieb Michal Srb:
> > > > The io_mem_pfn field was added in commit ea642c3216cb2a60d1c0e760ae47ee85c9c16447
> > > > and is called unconditionally. However, not all drivers were updated to set it.
> > > >
> > > > Use the ttm_bo_default_io_mem_pfn function if a driver did not set its own.
> > > >
> > > > Signed-off-by: Michal Srb <msrb@xxxxxxxx>
> > > NAK, when we have drivers missing this we should set this in the driver and
> > > not add the workaround here.
> > Why? What's the benefit in adding the same hook in 10 drivers (I was hoping
> > Michal would also remove the token .io_mem_pfn = ttm_bo_default_io_mem_pfn from
> > those as well)?
>
> Not have this extra check in common TTM code? That is seriously bad coding
> style.
>
[citation neeeded]
I'd argue it's bad form to require everyone add a copypasta hook to their driver
everytime an unrelated driver needs more control than the default gives :-)
I think your point would hold if we were talking about a couple of drivers, but
once you scale to 10+, it's no longer a trivial amount of code. If the null check
is too distracting, you could always pull it out into an inline.
Sean
> We have tons of fallbacks like this and I unfortunately even created new one
> without realizing that this is a problem.
>
> But this really clutters the TTM code and makes it harder to understand.
>
> Christian.
>
> >
> > Sean
> >
> > > Which driver is missing this? I thought I fixed all of them.
> > >
> > > Regards,
> > > Christian.
> > >
> > > > ---
> > > > drivers/gpu/drm/ttm/ttm_bo_vm.c | 5 ++++-
> > > > 1 file changed, 4 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > > > index c8ebb757e36b..e25a99bc519d 100644
> > > > --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > > > +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> > > > @@ -234,7 +234,10 @@ static int ttm_bo_vm_fault(struct vm_fault *vmf)
> > > > if (bo->mem.bus.is_iomem) {
> > > > /* Iomem should not be marked encrypted */
> > > > cvma.vm_page_prot = pgprot_decrypted(cvma.vm_page_prot);
> > > > - pfn = bdev->driver->io_mem_pfn(bo, page_offset);
> > > > + if (bdev->driver->io_mem_pfn)
> > > > + pfn = bdev->driver->io_mem_pfn(bo, page_offset);
> > > > + else
> > > > + pfn = ttm_bo_default_io_mem_pfn(bo, page_offset);
> > > > } else {
> > > > page = ttm->pages[page_offset];
> > > > if (unlikely(!page && i == 0)) {
> > > _______________________________________________
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> > > dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > > https://lists.freedesktop.org/mailman/listinfo/dri-devel
>
--
Sean Paul, Software Engineer, Google / Chromium OS
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