| Message ID | 20180705164357.28512-8-ville.syrjala@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Quoting Ville Syrjala (2018-07-05 17:43:56) > From: Ville Syrjälä <ville.syrjala@linux.intel.com> > > Make sure our hpd pin count doesn't exceed the bitmasks we use > for tracking pending hotplugs. Not ever close to the limit yet, > but no harm in making sure either. > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> > --- > drivers/gpu/drm/i915/i915_irq.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c > index bb7c754979f8..c107e0837026 100644 > --- a/drivers/gpu/drm/i915/i915_irq.c > +++ b/drivers/gpu/drm/i915/i915_irq.c > @@ -1713,6 +1713,8 @@ static void intel_get_hpd_pins(struct drm_i915_private *dev_priv, > { > enum hpd_pin pin; > > + BUILD_BUG_ON(HPD_NUM_PINS > 32); sizeof(*pin_mask) * CHAR_BIT ? Just looking for some explanation as where the limit comes from. Now obviously u32, but why was u32 chosen? -Chris
On Thu, Jul 05, 2018 at 05:52:16PM +0100, Chris Wilson wrote: > Quoting Ville Syrjala (2018-07-05 17:43:56) > > From: Ville Syrjälä <ville.syrjala@linux.intel.com> > > > > Make sure our hpd pin count doesn't exceed the bitmasks we use > > for tracking pending hotplugs. Not ever close to the limit yet, > > but no harm in making sure either. > > > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> > > --- > > drivers/gpu/drm/i915/i915_irq.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c > > index bb7c754979f8..c107e0837026 100644 > > --- a/drivers/gpu/drm/i915/i915_irq.c > > +++ b/drivers/gpu/drm/i915/i915_irq.c > > @@ -1713,6 +1713,8 @@ static void intel_get_hpd_pins(struct drm_i915_private *dev_priv, > > { > > enum hpd_pin pin; > > > > + BUILD_BUG_ON(HPD_NUM_PINS > 32); > > sizeof(*pin_mask) * CHAR_BIT ? For a slightly more pleasing appearance I suppose we might want to steal BITS_PER_TYPE() from include/linux/net_dim.h. A quick grep didn't seem to reveal anything similar in a more general location. > > Just looking for some explanation as where the limit comes from. Now > obviously u32, but why was u32 chosen? Had the right kind of smell perhaps?
Quoting Ville Syrjälä (2018-07-05 18:51:16) > On Thu, Jul 05, 2018 at 05:52:16PM +0100, Chris Wilson wrote: > > Quoting Ville Syrjala (2018-07-05 17:43:56) > > > From: Ville Syrjälä <ville.syrjala@linux.intel.com> > > > > > > Make sure our hpd pin count doesn't exceed the bitmasks we use > > > for tracking pending hotplugs. Not ever close to the limit yet, > > > but no harm in making sure either. > > > > > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> > > > --- > > > drivers/gpu/drm/i915/i915_irq.c | 2 ++ > > > 1 file changed, 2 insertions(+) > > > > > > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c > > > index bb7c754979f8..c107e0837026 100644 > > > --- a/drivers/gpu/drm/i915/i915_irq.c > > > +++ b/drivers/gpu/drm/i915/i915_irq.c > > > @@ -1713,6 +1713,8 @@ static void intel_get_hpd_pins(struct drm_i915_private *dev_priv, > > > { > > > enum hpd_pin pin; > > > > > > + BUILD_BUG_ON(HPD_NUM_PINS > 32); > > > > sizeof(*pin_mask) * CHAR_BIT ? > > For a slightly more pleasing appearance I suppose we might want > to steal BITS_PER_TYPE() from include/linux/net_dim.h. A quick > grep didn't seem to reveal anything similar in a more general > location. Yup, there's quite a few places that would be made more pleasant by BITS_PER_TYPE(). > > Just looking for some explanation as where the limit comes from. Now > > obviously u32, but why was u32 chosen? > > Had the right kind of smell perhaps? Ok, just curious if there was an intrinsic limit that could be captured alongside the assert. -Chris
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index bb7c754979f8..c107e0837026 100644 --- a/drivers/gpu/drm/i915/i915_irq.c +++ b/drivers/gpu/drm/i915/i915_irq.c @@ -1713,6 +1713,8 @@ static void intel_get_hpd_pins(struct drm_i915_private *dev_priv, { enum hpd_pin pin; + BUILD_BUG_ON(HPD_NUM_PINS > 32); + for_each_hpd_pin(pin) { if ((hpd[pin] & hotplug_trigger) == 0) continue;