On 17/09/15 14:20, Damien Lespiau wrote:
Not the first time! not the last time?
There is a possibility to use gcc 5's -Wbool-compare to try and compare
(reg) in those macros to a constant and gcc will warn that the
comparison between a boolean expression and a constant is always either
true or false. Maybe.
Since boolean true (1) cannot be a valid argument to this macro, it
could contain a compile-time check that the parameter is not 1; if
boolean false (0) happens not to be a valid register address (BSpec says
MMIO 0 is reserved) the macro could check that the argument is neither
of these values, and the compiler might then detect that all possible
paths lead to a compile-time error. Something like this?
#define I915_READ(reg) \
({ \
if (__builtin_constant_p(reg)) { \
BUILD_BUG_ON((reg) == false); \
BUILD_BUG_ON((reg) == true); \
} \
dev_priv->uncore.funcs.mmio_readl(dev_priv, (reg), true); \
})
Interestingly, that reported three errors, all in intel_dsi.c where the
port-selection macros use 0s to fill in dummy elements when less than 3
ports are being used.
In function ‘intel_dsi_get_hw_state’
In function ‘intel_dsi_port_disable’
In function ‘intel_dsi_port_enable’
Other than that, there weren't any cases where a bool constant was being
passed to this specific macro (as of today).
.Dave.
Cc: Imre Deak <imre.deak@xxxxxxxxx>
Signed-off-by: Damien Lespiau <damien.lespiau@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_ddi.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index 4823184..5b600bf 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -2882,7 +2882,7 @@ static bool bxt_ddi_pll_get_hw_state(struct drm_i915_private *dev_priv,
* here just read out lanes 0/1 and output a note if lanes 2/3 differ.
*/
hw_state->pcsdw12 = I915_READ(BXT_PORT_PCS_DW12_LN01(port));
- if (I915_READ(BXT_PORT_PCS_DW12_LN23(port) != hw_state->pcsdw12))
+ if (I915_READ(BXT_PORT_PCS_DW12_LN23(port)) != hw_state->pcsdw12)
DRM_DEBUG_DRIVER("lane stagger config different for lane 01 (%08x) and 23 (%08x)\n",
hw_state->pcsdw12,
I915_READ(BXT_PORT_PCS_DW12_LN23(port)));
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