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Linux Device Driver

Linux Device Driver. NCTU OS Lab Chi-Wei Yang. Outline. Overall Architecture Character Driver Block Driver Network Driver Support Functions. Overall Architecture. VFS Driver Types character block network. Overall Architecture (cont.). Overall Architecture (cont.). Operation Modes

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Linux Device Driver

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  1. Linux Device Driver NCTU OS Lab Chi-Wei Yang

  2. Outline • Overall Architecture • Character Driver • Block Driver • Network Driver • Support Functions

  3. Overall Architecture • VFS • Driver Types • character • block • network

  4. Overall Architecture (cont.)

  5. Overall Architecture (cont.) • Operation Modes • polling • interrupt • DMA

  6. Character Driver • Device Properties • can’t be randomly accessed • can’t be buffered • usually are slow devices • Export Interface • file_operations • Data Flow in read/write

  7. Character Driver (cont.)

  8. Block Driver • Device Properties • can be randomly accessed • accessed in units of blocks • to speed up access, buffer cache is used • Export Interface • file_operations • request_fn() • Data Flow in read/write

  9. Block Driver (cont.)

  10. Network Driver • Export Interface • Data Flow in read/write

  11. Network Driver (cont.)

  12. Network Driver (cont.)

  13. Support Functions • I/O ports reservations • request_region() • Memory Allocations • kmalloc(), vmalloc(), get_free_page() • Interrupt Handler Registration • request_irq() • Data Transfer between User/Kernel • memcpy_fromfs()

  14. Support Functions (cont.) • Bottom Halves • mark_bh() • its main purpose is to provide fewer blocking time due to interrupts • top half/bottom half • priority-based • limitions in writing bottom halves • can't call schedule(), can't block

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