The in-tree ublk driver doesn't need DMA alignment limit because there is one data copy between request pages and the userspace buffer. However, ublk is going to support zero copy, then DMA alignment limit is required, because same IO buffer is forwarded to backend which may have specific buffer DMA alignment limit, so the limit has to be exposed from the frontend driver to client application.
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| @@ -401,6 +401,11 @@ struct ublk_param_zoned { · 400 unmodified lines | ||
| 401 | 401 | __u8 reserved[20]; |
| 402 | 402 | }; |
| 403 | 403 | |
| 404 | +struct ublk_param_dma_align { | |
| 405 | + __u32 alignment; | |
| 406 | + __u8 pad[4]; | |
| 407 | +}; | |
| 408 | + | |
| 404 | 409 | struct ublk_params { |
| 405 | 410 | /* |
| 406 | 411 | * Total length of parameters, userspace has to set 'len' for both |
| @@ -413,12 +418,14 @@ struct ublk_params { · 6 unmodified lines | ||
| 413 | 418 | #define UBLK_PARAM_TYPE_DISCARD (1 << 1) |
| 414 | 419 | #define UBLK_PARAM_TYPE_DEVT (1 << 2) |
| 415 | 420 | #define UBLK_PARAM_TYPE_ZONED (1 << 3) |
| 421 | +#define UBLK_PARAM_TYPE_DMA_ALIGN (1 << 4) | |
| 416 | 422 | __u32 types; /* types of parameter included */ |
| 417 | 423 | |
| 418 | 424 | struct ublk_param_basic basic; |
| 419 | 425 | struct ublk_param_discard discard; |
| 420 | 426 | struct ublk_param_devt devt; |
| 421 | 427 | struct ublk_param_zoned zoned; |
| 428 | + struct ublk_param_dma_align dma; | |
| 422 | 429 | }; |
| 423 | 430 | |
| 424 | 431 | #endif |