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Reading 8- or 16-bit attributes from big-endian device returns 0 (#6166) #6175

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Reading 8- or 16-bit attributes from big-endian device returns 0 (#6166) #6175

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de63682
Reading 8- or 16-bit attributes from big-endian device returns 0 (#6166)
pjzander-signify Apr 20, 2021
fca3657
Rework on issue 6166
pjzander-signify Apr 21, 2021
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37 changes: 34 additions & 3 deletions src/app/util/af-types.h
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Original file line number Diff line number Diff line change
Expand Up @@ -88,6 +88,37 @@ typedef void (*EmberAfGenericClusterFunction)(void);
*/
#define EMBER_AF_NULL_MANUFACTURER_CODE 0x0000

/**
* @brief Type for align a 16 bits value.
*
* This structure has the same size as a pointer and is used to align
* a 16 bit value to the 16 least significant bits of a pointer.
* Note that this structure is aware of the endianess and the pointer size.
*/
typedef struct
{
#if defined(BIGENDIAN_CPU) && (BIGENDIAN_CPU != 0)
// Big endian
#if (UINTPTR_MAX == UINT32_MAX)
uint32_t align : 16;
uint16_t value;
#elif (UINTPTR_MAX == UINT64_MAX)
uint64_t align : 48;
uint16_t value;
Comment on lines +106 to +107
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This seems to be making assumptions about how a bitfield and an integer will pack that might not be valid in practice.... Nothing I'm aware of requires them to pack with no gaps here.

At the very least we should static_assert that sizeof(EmberAfAlignValue16) == sizeof(uint8_t*), right? That way we will catch it if things pack wrong.

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This seems to be making assumptions about how a bitfield and an integer will pack that might not be valid in practice.... Nothing I'm aware of requires them to pack with no gaps here.
You are right on that one.

#endif
#else
// Little endian
#if (UINTPTR_MAX == UINT32_MAX)
uint16_t value;
uint32_t align : 16;
#elif (UINTPTR_MAX == UINT64_MAX)
uint16_t value;
uint64_t align : 48;
#endif

#endif // defined(BIGENDIAN_CPU) && (BIGENDIAN_CPU != 0)
} EmberAfAlignValue16;

/**
* @brief Type for default values.
*
Expand All @@ -106,7 +137,7 @@ typedef union
/**
* Actual default value if the attribute size is 2 bytes or less.
*/
uint16_t defaultValue;
EmberAfAlignValue16 defaultValue;
} EmberAfDefaultAttributeValue;

/**
Expand Down Expand Up @@ -143,9 +174,9 @@ typedef union
*/
uint8_t * ptrToDefaultValue;
/**
* Actual default value if the attribute size is 2 bytes or less.
* Default value of the attribute.
Comment on lines -146 to +177
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Why this change to the comment? The new comment does not seem to be correct if the attribute type is larger than 2-byte; in that case this field is not really the default value in any sense; the ptrToDefaultValue points to where the default value is.

*/
uint16_t defaultValue;
EmberAfAlignValue16 defaultValue;
/**
* Points to the min max attribute value structure, if min/max is
* supported for this attribute.
Expand Down
4 changes: 2 additions & 2 deletions src/app/util/attribute-storage.cpp
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Expand Up @@ -1088,7 +1088,7 @@ void emAfLoadAttributeDefaults(EndpointId endpoint, bool writeTokens)
{
if (emberAfAttributeSize(am) <= 2)
{
ptr = (uint8_t *) &(am->defaultValue.ptrToMinMaxValue->defaultValue.defaultValue);
ptr = (uint8_t *) &(am->defaultValue.ptrToMinMaxValue->defaultValue.defaultValue.value);
}
else
{
Expand All @@ -1099,7 +1099,7 @@ void emAfLoadAttributeDefaults(EndpointId endpoint, bool writeTokens)
{
if (emberAfAttributeSize(am) <= 2)
{
ptr = (uint8_t *) &(am->defaultValue.defaultValue);
ptr = (uint8_t *) &(am->defaultValue.defaultValue.value);
}
else
{
Expand Down
4 changes: 2 additions & 2 deletions src/app/util/attribute-table.cpp
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Expand Up @@ -536,8 +536,8 @@ EmberAfStatus emAfWriteAttribute(EndpointId endpoint, ClusterId cluster, Attribu
if (dataLen <= 2)
{
int8_t minR, maxR;
uint8_t * minI = (uint8_t *) &(minv.defaultValue);
uint8_t * maxI = (uint8_t *) &(maxv.defaultValue);
uint8_t * minI = (uint8_t *) &(minv.defaultValue.value);
uint8_t * maxI = (uint8_t *) &(maxv.defaultValue.value);
// On big endian cpu with length 1 only the second byte counts
#if (BIGENDIAN_CPU)
if (dataLen == 1)
Expand Down