Process to generate various length parameters in a number of SGLS based upon the length fields of another SGL
View Patent ↗A method of generating length parameters, comprising the steps of reading a data stream from a host, detecting a particular field of the data stream, and calculating a variable based on a length parameter of a first list to be transferred. The data stream may comprise a plurality of definitions. The method may also comprise the step of selecting one of the list definitions. One of the list definitions may be used to generate a length parameter used in a second list in response to (i) the particular field of the data stream and (ii) the length parameter of the first list.
1. A method of generating length parameters, comprising the steps of: reading a data stream from a host, wherein said data stream comprises a plurality of list definitions including modes: (i) DMA, (ii) DMA data only, (iii) interleaved, or (iv) Data Integrity Field (DIF) only; detecting whether the data stream needs an inline data integrity field (DIF) or a separate data integrity field; calculating a number of blocks to be transferred based on a first length parameter of a first scattered gather list; and selecting one of said plurality of list definitions to generate a second length parameter used in a second scattered gather list in response to: (a) said detecting whether the data stream needs the inline data integrity field (DIF) or the separate data integrity field and (b) said first length parameter of said first scattered gather list and said calculated number of blocks.
2. The method according to claim 1 , wherein a first of said plurality of list definitions comprises the interleaved mode.
3. The method according to claim 2 , wherein said method further comprises: determining if said data stream comprising the first of said plurality of list definitions needs the inline data integrity field.
4. The method according to claim 3 , wherein said method further comprises: if said data stream comprising the first of said plurality of list needs the inline data integrity field, setting said second length parameter used in said second scattered gather list equal to said first length parameter of said first scattered gather list.
5. The method according to claim 3 , wherein said method further comprises: if said data stream comprising the first of said plurality of list definitions does not need the inline data integrity field, setting said second length parameter used in said second scattered gather list equal to said first length parameter of said first scattered gather list plus said calculated number of blocks.
6. The method according to claim 1 , wherein a second of said plurality of list definitions comprises the Data Integrity Field (DIF) only mode.
7. The method according to claim 6 , wherein said method further comprises: setting said second length parameter used in said second scattered gather list equal to said calculated number of blocks.
8. The method according to claim 1 , wherein a third of said plurality of list definitions comprises the Direct Memory Access (DMA) data only mode.
9. The method according to claim 8 , wherein said method further comprises: determining if said data stream comprising the third of said plurality of list definitions needs the inline data integrity field.
10. The method according to claim 9 , wherein said method further comprises: if said data stream comprising the third of said plurality of list definitions needs the inline data integrity field, setting said second length parameter used in said second scattered gather list equal to said first length parameter of said first scattered gather list.
11. The method according to claim 9 , wherein said method further comprises: if said data stream comprising the third of said plurality of list definitions does not need the inline data integrity field, setting said second length parameter used in said second scattered gather list equal to said first length parameter of said first scattered gather list minus said calculated number of blocks.
12. An apparatus comprising: a host configured to generate a data stream, wherein said data stream comprises a plurality of list definitions including modes: (i) DMA, (ii) DMA data only, (iii) interleaved, or (iv) Data Integrity Field (DIF) only; and a controller configured to: (i) detect whether the data stream needs an inline data integrity field (DIF) or a separate data integrity field, (ii) calculate a number of blocks to be transferred based on a first length parameter of a first scattered gather list, and (iii) select one of said plurality of list definitions to generate a second length parameter used in a second scattered gather list in response to: (a) said detect whether the data stream needs an inline data integrity field (DIF) or a separate data integrity field and (b) said first length parameter of said first scattered gather list and said calculated number of blocks.
13. The apparatus according to claim 12 , wherein a DMA engine generates said second length parameter used in said second scattered gather list.
14. The apparatus according to claim 13 , wherein said DMA engine comprises a cache memory to store said first length parameter of said first scattered gather list.