On 11/30/23 05:19, Johannes Thumshirn wrote:
On 30.11.23 02:34, Bart Van Assche wrote:+/* SBC-5 IO advice hints group descriptor */ +struct scsi_io_group_descriptor { +#if defined(__BIG_ENDIAN) + u8 io_advice_hints_mode: 2; + u8 reserved1: 3; + u8 st_enble: 1; + u8 cs_enble: 1; + u8 ic_enable: 1; +#elif defined(__LITTLE_ENDIAN) + u8 ic_enable: 1; + u8 cs_enble: 1; + u8 st_enble: 1; + u8 reserved1: 3; + u8 io_advice_hints_mode: 2; +#else +#error +#endif + u8 reserved2[3]; + /* Logical block markup descriptor */ +#if defined(__BIG_ENDIAN) + u8 acdlu: 1; + u8 reserved3: 1; + u8 rlbsr: 2; + u8 lbm_descriptor_type: 4; +#elif defined(__LITTLE_ENDIAN) + u8 lbm_descriptor_type: 4; + u8 rlbsr: 2; + u8 reserved3: 1; + u8 acdlu: 1; +#else +#error +#endif + u8 params[2]; + u8 reserved4; + u8 reserved5[8]; +}; + +static_assert(sizeof(struct scsi_io_group_descriptor) == 16);Have you considered using GENMASK() and FILED_GET() for this? All the ifdefs make the header rather ugly.
Hi Johannes, When using bitfields, there are #ifdefs in the data structure definitions but it is easy to write code that accesses the bitfields. When using FIELD_GET(), the data structure definitions have no ifdefs but the code that reads bitfields becomes harder to verify. The code for setting bitfield values would have to use FIELD_PREP() and hence would become more complex. An example of code that sets bitfields is the definition of the gr_m_pg data structure in patch 15/17 of this series. It would become more complicated if FIELD_PREP() would have to be used in the definition of that data structure. Thanks, Bart.
