€•mh      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”(hhŒparent”hubaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ$/translations/zh_CN/core-api/packing”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”(hhhh2ubah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ$/translations/zh_TW/core-api/packing”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”(hhhhFubah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ$/translations/it_IT/core-api/packing”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”(hhhhZubah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ$/translations/ja_JP/core-api/packing”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”(hhhhnubah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ$/translations/ko_KR/core-api/packing”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”(hhhh‚ubah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ$/translations/sp_SP/core-api/packing”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒ0Generic bitfield packing and unpacking functions”h]”hŒ0Generic bitfield packing and unpacking functions”…””}”(hhªhh¨hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh£hžhhŸŒ>/var/lib/git/docbuild/linux/Documentation/core-api/packing.rst”h Kubh¢)”}”(hhh]”(h§)”}”(hŒProblem statement”h]”hŒProblem statement”…””}”(hh¼hhºhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh·hžhhŸh¶h KubhŒ	paragraph”“”)”}”(hXš  When working with hardware, one has to choose between several approaches of
interfacing with it.
One can memory-map a pointer to a carefully crafted struct over the hardware
device's memory region, and access its fields as struct members (potentially
declared as bitfields). But writing code this way would make it less portable,
due to potential endianness mismatches between the CPU and the hardware device.
Additionally, one has to pay close attention when translating register
definitions from the hardware documentation into bit field indices for the
structs. Also, some hardware (typically networking equipment) tends to group
its register fields in ways that violate any reasonable word boundaries
(sometimes even 64 bit ones). This creates the inconvenience of having to
define "high" and "low" portions of register fields within the struct.
A more robust alternative to struct field definitions would be to extract the
required fields by shifting the appropriate number of bits. But this would
still not protect from endianness mismatches, except if all memory accesses
were performed byte-by-byte. Also the code can easily get cluttered, and the
high-level idea might get lost among the many bit shifts required.
Many drivers take the bit-shifting approach and then attempt to reduce the
clutter with tailored macros, but more often than not these macros take
shortcuts that still prevent the code from being truly portable.”h]”hX¤  When working with hardware, one has to choose between several approaches of
interfacing with it.
One can memory-map a pointer to a carefully crafted struct over the hardware
deviceâ€™s memory region, and access its fields as struct members (potentially
declared as bitfields). But writing code this way would make it less portable,
due to potential endianness mismatches between the CPU and the hardware device.
Additionally, one has to pay close attention when translating register
definitions from the hardware documentation into bit field indices for the
structs. Also, some hardware (typically networking equipment) tends to group
its register fields in ways that violate any reasonable word boundaries
(sometimes even 64 bit ones). This creates the inconvenience of having to
define â€œhighâ€ and â€œlowâ€ portions of register fields within the struct.
A more robust alternative to struct field definitions would be to extract the
required fields by shifting the appropriate number of bits. But this would
still not protect from endianness mismatches, except if all memory accesses
were performed byte-by-byte. Also the code can easily get cluttered, and the
high-level idea might get lost among the many bit shifts required.
Many drivers take the bit-shifting approach and then attempt to reduce the
clutter with tailored macros, but more often than not these macros take
shortcuts that still prevent the code from being truly portable.”…””}”(hhÌhhÊhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h Khh·hžhubeh}”(h]”Œproblem-statement”ah ]”h"]”Œproblem statement”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kubh¢)”}”(hhh]”(h§)”}”(hŒThe solution”h]”hŒThe solution”…””}”(hhåhhãhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hhàhžhhŸh¶h KubhÉ)”}”(hŒ'This API deals with 2 basic operations:”h]”hŒ'This API deals with 2 basic operations:”…””}”(hhóhhñhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h K hhàhžhubhŒblock_quote”“”)”}”(hhh]”hŒbullet_list”“”)”}”(hhh]”(hŒ	list_item”“”)”}”(hŒSPacking a CPU-usable number into a memory buffer (with hardware
constraints/quirks)”h]”hÉ)”}”(hŒSPacking a CPU-usable number into a memory buffer (with hardware
constraints/quirks)”h]”hŒSPacking a CPU-usable number into a memory buffer (with hardware
constraints/quirks)”…””}”(hj  hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h K"hj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j	  hj  ubj
  )”}”(hŒ\Unpacking a memory buffer (which has hardware constraints/quirks)
into a CPU-usable number.
”h]”hÉ)”}”(hŒ[Unpacking a memory buffer (which has hardware constraints/quirks)
into a CPU-usable number.”h]”hŒ[Unpacking a memory buffer (which has hardware constraints/quirks)
into a CPU-usable number.”…””}”(hj)  hj'  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h K$hj#  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j	  hj  ubeh}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ-”uh1j  hŸh¶h K"hj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1hÿhhàhžhhŸNh NubhÉ)”}”(hŒ—The API offers an abstraction over said hardware constraints and quirks,
over CPU endianness and therefore between possible mismatches between
the two.”h]”hŒ—The API offers an abstraction over said hardware constraints and quirks,
over CPU endianness and therefore between possible mismatches between
the two.”…””}”(hjK  hjI  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h K'hhàhžhubhÉ)”}”(hŒÉThe basic unit of these API functions is the u64. From the CPU's
perspective, bit 63 always means bit offset 7 of byte 7, albeit only
logically. The question is: where do we lay this bit out in memory?”h]”hŒËThe basic unit of these API functions is the u64. From the CPUâ€™s
perspective, bit 63 always means bit offset 7 of byte 7, albeit only
logically. The question is: where do we lay this bit out in memory?”…””}”(hjY  hjW  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h K+hhàhžhubhÉ)”}”(hŒÎThe following examples cover the memory layout of a packed u64 field.
The byte offsets in the packed buffer are always implicitly 0, 1, ... 7.
What the examples show is where the logical bytes and bits sit.”h]”hŒÎThe following examples cover the memory layout of a packed u64 field.
The byte offsets in the packed buffer are always implicitly 0, 1, ... 7.
What the examples show is where the logical bytes and bits sit.”…””}”(hjg  hje  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h K/hhàhžhubhŒenumerated_list”“”)”}”(hhh]”j
  )”}”(hŒ0Normally (no quirks), we would do it like this:
”h]”hÉ)”}”(hŒ/Normally (no quirks), we would do it like this:”h]”hŒ/Normally (no quirks), we would do it like this:”…””}”(hj~  hj|  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h K3hjx  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j	  hju  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”Œenumtype”Œarabic”Œprefix”hŒsuffix”Œ.”uh1js  hhàhžhhŸh¶h K3ubhŒliteral_block”“”)”}”(hXU  63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32
7                       6                       5                        4
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0
3                       2                       1                        0”h]”hXU  63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32
7                       6                       5                        4
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0
3                       2                       1                        0”…””}”(hhhj  ubah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1j›  hŸh¶h K7hhàhžhubhÉ)”}”(hX2  That is, the MSByte (7) of the CPU-usable u64 sits at memory offset 0, and the
LSByte (0) of the u64 sits at memory offset 7.
This corresponds to what most folks would regard to as "big endian", where
bit i corresponds to the number 2^i. This is also referred to in the code
comments as "logical" notation.”h]”hX:  That is, the MSByte (7) of the CPU-usable u64 sits at memory offset 0, and the
LSByte (0) of the u64 sits at memory offset 7.
This corresponds to what most folks would regard to as â€œbig endianâ€, where
bit i corresponds to the number 2^i. This is also referred to in the code
comments as â€œlogicalâ€ notation.”…””}”(hj¯  hj­  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h K<hhàhžhubjt  )”}”(hhh]”j
  )”}”(hŒ6If QUIRK_MSB_ON_THE_RIGHT is set, we do it like this:
”h]”hÉ)”}”(hŒ5If QUIRK_MSB_ON_THE_RIGHT is set, we do it like this:”h]”hŒ5If QUIRK_MSB_ON_THE_RIGHT is set, we do it like this:”…””}”(hjÄ  hjÂ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h KChj¾  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j	  hj»  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j–  j—  j˜  hj™  jš  Œstart”Kuh1js  hhàhžhhŸh¶h KCubjœ  )”}”(hXU  56 57 58 59 60 61 62 63 48 49 50 51 52 53 54 55 40 41 42 43 44 45 46 47 32 33 34 35 36 37 38 39
7                       6                        5                       4
24 25 26 27 28 29 30 31 16 17 18 19 20 21 22 23  8  9 10 11 12 13 14 15  0  1  2  3  4  5  6  7
3                       2                        1                       0”h]”hXU  56 57 58 59 60 61 62 63 48 49 50 51 52 53 54 55 40 41 42 43 44 45 46 47 32 33 34 35 36 37 38 39
7                       6                        5                       4
24 25 26 27 28 29 30 31 16 17 18 19 20 21 22 23  8  9 10 11 12 13 14 15  0  1  2  3  4  5  6  7
3                       2                        1                       0”…””}”(hhhjÝ  ubah}”(h]”h ]”h"]”h$]”h&]”j«  j¬  uh1j›  hŸh¶h KGhhàhžhubhÉ)”}”(hŒhThat is, QUIRK_MSB_ON_THE_RIGHT does not affect byte positioning, but
inverts bit offsets inside a byte.”h]”hŒhThat is, QUIRK_MSB_ON_THE_RIGHT does not affect byte positioning, but
inverts bit offsets inside a byte.”…””}”(hjí  hjë  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h KLhhàhžhubjt  )”}”(hhh]”j
  )”}”(hŒ3If QUIRK_LITTLE_ENDIAN is set, we do it like this:
”h]”hÉ)”}”(hŒ2If QUIRK_LITTLE_ENDIAN is set, we do it like this:”h]”hŒ2If QUIRK_LITTLE_ENDIAN is set, we do it like this:”…””}”(hj  hj   hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h KPhjü  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j	  hjù  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j–  j—  j˜  hj™  jš  jÜ  Kuh1js  hhàhžhhŸh¶h KPubjœ  )”}”(hXS  39 38 37 36 35 34 33 32 47 46 45 44 43 42 41 40 55 54 53 52 51 50 49 48 63 62 61 60 59 58 57 56
4                       5                       6                       7
7  6  5  4  3  2  1  0  15 14 13 12 11 10  9  8 23 22 21 20 19 18 17 16 31 30 29 28 27 26 25 24
0                       1                       2                       3”h]”hXS  39 38 37 36 35 34 33 32 47 46 45 44 43 42 41 40 55 54 53 52 51 50 49 48 63 62 61 60 59 58 57 56
4                       5                       6                       7
7  6  5  4  3  2  1  0  15 14 13 12 11 10  9  8 23 22 21 20 19 18 17 16 31 30 29 28 27 26 25 24
0                       1                       2                       3”…””}”(hhhj  ubah}”(h]”h ]”h"]”h$]”h&]”j«  j¬  uh1j›  hŸh¶h KThhàhžhubhÉ)”}”(hŒ®Therefore, QUIRK_LITTLE_ENDIAN means that inside the memory region, every
byte from each 4-byte word is placed at its mirrored position compared to
the boundary of that word.”h]”hŒ®Therefore, QUIRK_LITTLE_ENDIAN means that inside the memory region, every
byte from each 4-byte word is placed at its mirrored position compared to
the boundary of that word.”…””}”(hj*  hj(  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h KYhhàhžhubjt  )”}”(hhh]”j
  )”}”(hŒTIf QUIRK_MSB_ON_THE_RIGHT and QUIRK_LITTLE_ENDIAN are both set, we do it
like this:
”h]”hÉ)”}”(hŒSIf QUIRK_MSB_ON_THE_RIGHT and QUIRK_LITTLE_ENDIAN are both set, we do it
like this:”h]”hŒSIf QUIRK_MSB_ON_THE_RIGHT and QUIRK_LITTLE_ENDIAN are both set, we do it
like this:”…””}”(hj?  hj=  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h K]hj9  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j	  hj6  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j–  j—  j˜  hj™  jš  jÜ  Kuh1js  hhàhžhhŸh¶h K]ubjœ  )”}”(hXS  32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
4                       5                       6                       7
0  1  2  3  4  5  6  7  8   9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
0                       1                       2                       3”h]”hXS  32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
4                       5                       6                       7
0  1  2  3  4  5  6  7  8   9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
0                       1                       2                       3”…””}”(hhhjW  ubah}”(h]”h ]”h"]”h$]”h&]”j«  j¬  uh1j›  hŸh¶h Kbhhàhžhubjt  )”}”(hhh]”j
  )”}”(hŒ9If just QUIRK_LSW32_IS_FIRST is set, we do it like this:
”h]”hÉ)”}”(hŒ8If just QUIRK_LSW32_IS_FIRST is set, we do it like this:”h]”hŒ8If just QUIRK_LSW32_IS_FIRST is set, we do it like this:”…””}”(hjn  hjl  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h Khhjh  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j	  hje  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j–  j—  j˜  hj™  jš  jÜ  Kuh1js  hhàhžhhŸh¶h Khubjœ  )”}”(hXU  31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0
3                       2                       1                        0
63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32
7                       6                       5                        4”h]”hXU  31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10  9  8  7  6  5  4  3  2  1  0
3                       2                       1                        0
63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32
7                       6                       5                        4”…””}”(hhhj†  ubah}”(h]”h ]”h"]”h$]”h&]”j«  j¬  uh1j›  hŸh¶h KlhhàhžhubhÉ)”}”(hŒ±In this case the 8 byte memory region is interpreted as follows: first
4 bytes correspond to the least significant 4-byte word, next 4 bytes to
the more significant 4-byte word.”h]”hŒ±In this case the 8 byte memory region is interpreted as follows: first
4 bytes correspond to the least significant 4-byte word, next 4 bytes to
the more significant 4-byte word.”…””}”(hj–  hj”  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h Kqhhàhžhubjt  )”}”(hhh]”j
  )”}”(hŒPIf QUIRK_LSW32_IS_FIRST and QUIRK_MSB_ON_THE_RIGHT are set, we do it like
this:
”h]”hÉ)”}”(hŒOIf QUIRK_LSW32_IS_FIRST and QUIRK_MSB_ON_THE_RIGHT are set, we do it like
this:”h]”hŒOIf QUIRK_LSW32_IS_FIRST and QUIRK_MSB_ON_THE_RIGHT are set, we do it like
this:”…””}”(hj«  hj©  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h Kvhj¥  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j	  hj¢  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j–  j—  j˜  hj™  jš  jÜ  Kuh1js  hhàhžhhŸh¶h Kvubjœ  )”}”(hXU  24 25 26 27 28 29 30 31 16 17 18 19 20 21 22 23  8  9 10 11 12 13 14 15  0  1  2  3  4  5  6  7
3                       2                        1                       0
56 57 58 59 60 61 62 63 48 49 50 51 52 53 54 55 40 41 42 43 44 45 46 47 32 33 34 35 36 37 38 39
7                       6                        5                       4”h]”hXU  24 25 26 27 28 29 30 31 16 17 18 19 20 21 22 23  8  9 10 11 12 13 14 15  0  1  2  3  4  5  6  7
3                       2                        1                       0
56 57 58 59 60 61 62 63 48 49 50 51 52 53 54 55 40 41 42 43 44 45 46 47 32 33 34 35 36 37 38 39
7                       6                        5                       4”…””}”(hhhjÃ  ubah}”(h]”h ]”h"]”h$]”h&]”j«  j¬  uh1j›  hŸh¶h K{hhàhžhubjt  )”}”(hhh]”j
  )”}”(hŒMIf QUIRK_LSW32_IS_FIRST and QUIRK_LITTLE_ENDIAN are set, it looks like
this:
”h]”hÉ)”}”(hŒLIf QUIRK_LSW32_IS_FIRST and QUIRK_LITTLE_ENDIAN are set, it looks like
this:”h]”hŒLIf QUIRK_LSW32_IS_FIRST and QUIRK_LITTLE_ENDIAN are set, it looks like
this:”…””}”(hjÚ  hjØ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h KhjÔ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j	  hjÑ  hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j–  j—  j˜  hj™  jš  jÜ  Kuh1js  hhàhžhhŸh¶h Kubjœ  )”}”(hXS  7  6  5  4  3  2  1  0  15 14 13 12 11 10  9  8 23 22 21 20 19 18 17 16 31 30 29 28 27 26 25 24
0                       1                       2                       3
39 38 37 36 35 34 33 32 47 46 45 44 43 42 41 40 55 54 53 52 51 50 49 48 63 62 61 60 59 58 57 56
4                       5                       6                       7”h]”hXS  7  6  5  4  3  2  1  0  15 14 13 12 11 10  9  8 23 22 21 20 19 18 17 16 31 30 29 28 27 26 25 24
0                       1                       2                       3
39 38 37 36 35 34 33 32 47 46 45 44 43 42 41 40 55 54 53 52 51 50 49 48 63 62 61 60 59 58 57 56
4                       5                       6                       7”…””}”(hhhjò  ubah}”(h]”h ]”h"]”h$]”h&]”j«  j¬  uh1j›  hŸh¶h K†hhàhžhubjt  )”}”(hhh]”j
  )”}”(hŒeIf QUIRK_LSW32_IS_FIRST, QUIRK_LITTLE_ENDIAN and QUIRK_MSB_ON_THE_RIGHT
are set, it looks like this:
”h]”hÉ)”}”(hŒdIf QUIRK_LSW32_IS_FIRST, QUIRK_LITTLE_ENDIAN and QUIRK_MSB_ON_THE_RIGHT
are set, it looks like this:”h]”hŒdIf QUIRK_LSW32_IS_FIRST, QUIRK_LITTLE_ENDIAN and QUIRK_MSB_ON_THE_RIGHT
are set, it looks like this:”…””}”(hj	  hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h KŒhj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j	  hj   hžhhŸh¶h Nubah}”(h]”h ]”h"]”h$]”h&]”j–  j—  j˜  hj™  jš  jÜ  Kuh1js  hhàhžhhŸh¶h KŒubjœ  )”}”(hXS  0  1  2  3  4  5  6  7  8   9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
0                       1                       2                       3
32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
4                       5                       6                       7”h]”hXS  0  1  2  3  4  5  6  7  8   9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
0                       1                       2                       3
32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
4                       5                       6                       7”…””}”(hhhj!  ubah}”(h]”h ]”h"]”h$]”h&]”j«  j¬  uh1j›  hŸh¶h K‘hhàhžhubhÉ)”}”(hŒWe always think of our offsets as if there were no quirk, and we translate
them afterwards, before accessing the memory region.”h]”hŒWe always think of our offsets as if there were no quirk, and we translate
them afterwards, before accessing the memory region.”…””}”(hj1  hj/  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h K—hhàhžhubeh}”(h]”Œthe-solution”ah ]”h"]”Œthe solution”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kubh¢)”}”(hhh]”(h§)”}”(hŒIntended use”h]”hŒIntended use”…””}”(hjJ  hjH  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjE  hžhhŸh¶h K›ubhÉ)”}”(hX'  Drivers that opt to use this API first need to identify which of the above 3
quirk combinations (for a total of 8) match what the hardware documentation
describes. Then they should wrap the packing() function, creating a new
xxx_packing() that calls it using the proper QUIRK_* one-hot bits set.”h]”hX'  Drivers that opt to use this API first need to identify which of the above 3
quirk combinations (for a total of 8) match what the hardware documentation
describes. Then they should wrap the packing() function, creating a new
xxx_packing() that calls it using the proper QUIRK_* one-hot bits set.”…””}”(hjX  hjV  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h KhjE  hžhubhÉ)”}”(hXB  The packing() function returns an int-encoded error code, which protects the
programmer against incorrect API use.  The errors are not expected to occur
during runtime, therefore it is reasonable for xxx_packing() to return void
and simply swallow those errors. Optionally it can dump stack or print the
error description.”h]”hXB  The packing() function returns an int-encoded error code, which protects the
programmer against incorrect API use.  The errors are not expected to occur
during runtime, therefore it is reasonable for xxx_packing() to return void
and simply swallow those errors. Optionally it can dump stack or print the
error description.”…””}”(hjf  hjd  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhŸh¶h K¢hjE  hžhubeh}”(h]”Œintended-use”ah ]”h"]”Œintended use”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K›ubeh}”(h]”Œ0generic-bitfield-packing-and-unpacking-functions”ah ]”h"]”Œ0generic bitfield packing and unpacking functions”ah$]”h&]”uh1h¡hhhžhhŸh¶h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h¶uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¦NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”j¥  Œerror_encoding”ŒUTF-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”h¶Œ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œembed_images”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(j  j|  hÝhÚjB  j?  jw  jt  uŒ	nametypes”}”(j  NhÝNjB  Njw  Nuh}”(j|  h£hÚh·j?  hàjt  jE  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”(hŒsystem_message”“”)”}”(hhh]”hÉ)”}”(hŒ:Enumerated list start value not ordinal-1: "2" (ordinal 2)”h]”hŒ>Enumerated list start value not ordinal-1: â€œ2â€ (ordinal 2)”…””}”(hhhj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhj
  ubah}”(h]”h ]”h"]”h$]”h&]”Œlevel”KŒtype”ŒINFO”Œsource”h¶Œline”Kuh1j  hhàhžhhŸh¶h KCubj	  )”}”(hhh]”hÉ)”}”(hŒ:Enumerated list start value not ordinal-1: "3" (ordinal 3)”h]”hŒ>Enumerated list start value not ordinal-1: â€œ3â€ (ordinal 3)”…””}”(hhhj)  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhj&  ubah}”(h]”h ]”h"]”h$]”h&]”Œlevel”KŒtype”j#  Œsource”h¶Œline”Kuh1j  hhàhžhhŸh¶h KPubj	  )”}”(hhh]”hÉ)”}”(hŒ:Enumerated list start value not ordinal-1: "4" (ordinal 4)”h]”hŒ>Enumerated list start value not ordinal-1: â€œ4â€ (ordinal 4)”…””}”(hhhjD  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhjA  ubah}”(h]”h ]”h"]”h$]”h&]”Œlevel”KŒtype”j#  Œsource”h¶Œline”Kuh1j  hhàhžhhŸh¶h K]ubj	  )”}”(hhh]”hÉ)”}”(hŒ:Enumerated list start value not ordinal-1: "5" (ordinal 5)”h]”hŒ>Enumerated list start value not ordinal-1: â€œ5â€ (ordinal 5)”…””}”(hhhj_  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhj\  ubah}”(h]”h ]”h"]”h$]”h&]”Œlevel”KŒtype”j#  Œsource”h¶Œline”Kuh1j  hhàhžhhŸh¶h Khubj	  )”}”(hhh]”hÉ)”}”(hŒ:Enumerated list start value not ordinal-1: "6" (ordinal 6)”h]”hŒ>Enumerated list start value not ordinal-1: â€œ6â€ (ordinal 6)”…””}”(hhhjz  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhjw  ubah}”(h]”h ]”h"]”h$]”h&]”Œlevel”KŒtype”j#  Œsource”h¶Œline”Kuh1j  hhàhžhhŸh¶h Kvubj	  )”}”(hhh]”hÉ)”}”(hŒ:Enumerated list start value not ordinal-1: "7" (ordinal 7)”h]”hŒ>Enumerated list start value not ordinal-1: â€œ7â€ (ordinal 7)”…””}”(hhhj•  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhj’  ubah}”(h]”h ]”h"]”h$]”h&]”Œlevel”KŒtype”j#  Œsource”h¶Œline”Kuh1j  hhàhžhhŸh¶h Kubj	  )”}”(hhh]”hÉ)”}”(hŒ:Enumerated list start value not ordinal-1: "8" (ordinal 8)”h]”hŒ>Enumerated list start value not ordinal-1: â€œ8â€ (ordinal 8)”…””}”(hhhj°  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÈhj­  ubah}”(h]”h ]”h"]”h$]”h&]”Œlevel”KŒtype”j#  Œsource”h¶Œline”Kuh1j  hhàhžhhŸh¶h KŒubeŒtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nhžhub.