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drm/i915: fix potential dangling else problems in for_each_ macros

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We have serious dangling else bugs waiting to happen in our for_each_
style macros with ifs. Consider, for example,

 #define for_each_power_domain(domain, mask)                         \
         for ((domain) = 0; (domain) < POWER_DOMAIN_NUM; (domain)++) \
                 if ((1 << (domain)) & (mask))

If this is used in context:

	if (condition)
		for_each_power_domain(domain, mask);
	else
		foo();

foo() will be called for each domain *not* in mask, if condition holds,
and not at all if condition doesn't hold.

Fix this by reversing the conditions in the macros, and adding an else
branch for the "for each" block, so that other if/else blocks can't
interfere. Provide a "for_each_if" helper macro to make it easier to get
this right.

v2: move for_each_if to drmP.h in a separate patch.

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1448392916-2281-2-git-send-email-jani.nikula@intel.com
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Jani Nikula
2015-11-24 21:21:56 +02:00
committed by Daniel Vetter
parent 373701b1fc
commit 95150bdf78
4 changed files with 10 additions and 10 deletions
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2
drivers/gpu/drm/i915/intel_dsi.h
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@@ -117,7 +117,7 @@ static inline struct intel_dsi_host *to_intel_dsi_host(struct mipi_dsi_host *h)
#define for_each_dsi_port(__port, __ports_mask) \
for ((__port) = PORT_A; (__port) < I915_MAX_PORTS; (__port)++) \
if ((__ports_mask) & (1 << (__port)))
for_each_if ((__ports_mask) & (1 << (__port)))
static inline struct intel_dsi *enc_to_intel_dsi(struct drm_encoder *encoder)
{