On Wed, 2013-09-11 at 11:21 +0300, Jani Nikula wrote:
> On Wed, 11 Sep 2013, Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> wrote:
> > From: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
> >
> > Boot params quirks_set and quirks_mask allow the user to enable or
> > inhibit any dmi-matched quirks, overriding the dmi match table. Examples:
> >
> > i915.quirks_set=0x2 - enables QUIRK_LVDS_SSC_DISABLE
> > i915.quirks_set=0x8 - enables QUIRK_NO_PCH_PWM_ENABLE
> > i915.quirks_mask=0x8 - disables QUIRK_NO_PCH_PWM_ENABLE
> > i915.quirks_mask=0xFF - disables all quirks
Thanks for reviewing this, Jani. I hope you're open to a little more
debate on the topic...
> While I admit this can be used to workaround issues with certain
> machines, this is a hack that exposes an implementation detail to the
> userspace, and carves it into the stone. Any user of it would have to
> look at the kernel source to make a smart choice of parameters; more
> likely forums would start filling with tips what to set.
All of the above is true of all boot params. Why is that a problem?
Consider that if this quirks_set/mask feature were available:
- Users and developers could trivially check whether any future machine
needs to be added to any of the existing dmi-match quirk tables.
Currently we have to build a test kernel and get the user to install it,
but this would allow us to just ask "Does i915.quirks_set=0x2 fix it?".
That feature alone makes me want quirks_set/mask.
- We would unblock some black-screen-on-boot users who currently have
no other solution. And we would unblock future users who face future
dmi/quirk-mismatch issues (of which I am sure there will be more).
- The existing i915.invert_brightness override param would not have
been needed. (It is worth nothing also that my previously proposed
i915.disable_pch_pwm override patch was rejected, even though its
implementation is identical to invert_brightness.)
> So NAK from me.
>
> That said, I think we still have a few stones unturned wrt backlight and
> what BIOS does in UEFI mode.
I would be thrilled to see the UEFI/BIOS/backlight issue get fixed, but
in my opinion i915.quirks_set/mask would be very useful (a) anyway, and
(b) immediately.
-Kamal
>
> Cheers,
> Jani.
>
> >
> > Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/intel_display.c | 15 +++++++++++++++
> > 1 file changed, 15 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index 1eabca3..12607f2 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -10043,8 +10043,19 @@ static struct intel_quirk intel_quirks[] = {
> > { 0x0166, 0x1028, 0x058b, quirk_no_pcm_pwm_enable },
> > };
> >
> > +unsigned long i915_quirks_set __read_mostly = 0;
> > +module_param_named(quirks_set, i915_quirks_set, ulong, 0600);
> > +MODULE_PARM_DESC(quirks_set,
> > + "Enable specified quirks bits.");
> > +
> > +unsigned long i915_quirks_mask __read_mostly = 0;
> > +module_param_named(quirks_mask, i915_quirks_mask, ulong, 0600);
> > +MODULE_PARM_DESC(quirks_mask,
> > + "Disable specified quirks bits (override dmi match).");
> > +
> > static void intel_init_quirks(struct drm_device *dev)
> > {
> > + struct drm_i915_private *dev_priv = dev->dev_private;
> > struct pci_dev *d = dev->pdev;
> > int i;
> >
> > @@ -10062,6 +10073,10 @@ static void intel_init_quirks(struct drm_device *dev)
> > if (dmi_check_system(*intel_dmi_quirks[i].dmi_id_list) != 0)
> > intel_dmi_quirks[i].hook(dev);
> > }
> > +
> > + /* handle user-specified quirks overrides */
> > + dev_priv->quirks |= i915_quirks_set;
> > + dev_priv->quirks &= ~i915_quirks_mask;
> > }
> >
> > /* Disable the VGA plane that we never use */
> > --
> > 1.8.1.4
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
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