busdma
The busdma interfaces permit hardware device drivers to operate on a variety of platforms avoiding the encoding of platform-specific access methods into drivers. This lowers the maintenance costs for drivers across platforms, and improves the chances that a driver will "just work" on a new platform. Modifying a driver to make use of busdma is relatively straight forward, but does require familiarity with both the device driver and busdma primitives. For busdma to be used in FreeBSD, two sets of changes are generally required: adaptation of the busdma implementation to run on all platforms, and adaptation of drivers to use the framework. As such, status information on this project is broken down into platform support, and driver support (sorted by category). Completing this work requires a thorough audit of the system device drivers, then prioritized conversion of drivers.
INTR_MPSAFE
Hardware drivers register their interrupt handler with the
bus_setup_intr() function. Setting the flag
INTR_MPSAFE tells the system interrupt code to
call the interrupt routine without holding the Giant mutex.
This can give a significant performance gain on SMP
systems.
Drivers can set this flag even if they are not fully locked down as long as their interrupt routine is careful about not touching other data structures in the driver. An easy way to do this is to check and clear the hardware interrupt status registers and then schedule the interrupt processing for a taskqueue or kernel thread.
SMPng locked
Drivers should employ mutexes and sx locks to protect their data structures and hardware registers from competing threads. Mutex operations are somewhat expensive, so a good strategy is combine as many atomic operations into a single mutex acquisition as possible.
p!=a safety
Intel PAE support requires that pointers and physical address representations be of differing sizes. This means that drivers must be written to use vm_paddr_t or bus_addr_t rather than assuming that physical addresses can be represented using a void *. In addition, format strings and casts must be carefully handled.
The task list below is not intended to be complete, but does represent a set of relevant and/or important components of the overall work. The "Responsible" field identifies a developer who has expressed willingness to be responsible for completing the identified task; this doesn't preclude others working on it, but suggests that coordination with the responsible party might be appropriate so as to avoid unnecessary duplication of work, and to maximize forward progress. If beginning work on a new area of substantial size, or one that appears unclaimed, it may be worth dropping an e-mail to Maxime Henrion to see if any progress has been made.
The definition of the date field varies depending on the status of a task. For completed tasks, it refers to the date completed or reported completed. For in-progress tasks, it refers to the date of the last update of the entry. For stalled tasks, it refers to the date that the task was declared stalled. For new tasks, it refers to the date the task was added to the list.
Tasks are sorted first by status, then by date.
| Task | Responsible | Last updated | Status | Details |
|---|---|---|---|---|
| alpha | Andrew Gallatin | December 10, 2002 | Done | There may be problems for systems with large amounts of memory. |
| amd64 | Peter Wemm | July 1, 2003 | Done | Fully supported. |
| ia64 | Marcel Moolenaar | December 10, 2002 | Done | There may be problems for systems with large amounts of memory. |
| i386 | Sam Leffler | December 9, 2002 | Done | Fully supported. |
| powerpc | Hiten Pandya | January 15, 2003 | Done | Fully supported. |
| sparc64 | Thomas Moestl | January 6, 2003 | Done | Fully supported. |
| Driver | Responsible | Last updated | busdma | INTR_MPSAFE | SMPng locked | a!=p | Notes | |
|---|---|---|---|---|---|---|---|---|
| if_ar | Not done | Not done | Not done | Not done | kvtop() | |||
| if_bge | Bill Paul | July 26, 2003 | Needs testing | Not done | Not done | Done | ||
| if_cs | Not done | Not done | Not done | Not done | ||||
| if_dc | Maxime Henrion | April 17, 2003 | Done | Not done | Not done | Needs testing | ||
| if_de | Maxime Henrion | Not done | Not done | Not done | Not done | vtophys() | ||
| if_ed | Not done | Not done | Not done | Not done | kvtop() | |||
| if_em | Prafulla Deuskar | December 19, 2002 | Done | Not done | Not done | Done | ||
| if_en | Harti Brandt | March 4, 2003 | Done | Not done | Not done | Needs testing | ||
| if_fxp | Maxime Henrion | December 9, 2002 | Done | Not done | Not done | Done | ||
| if_fwe | Not done | Not done | Not done | Not done | ||||
| if_gem | Thomas Moestl | January 6, 2003 | Done | Not done | Not done | Not done | ||
| if_gx | Not done | Not done | Not done | Not done | vtophys() | |||
| if_hme | Thomas Moestl | January 6, 2003 | Done | Not done | Not done | Not done | ||
| if_idt | Not done | Not done | Not done | Not done | vtophys() | |||
| if_lge | Not done | Not done | Not done | Not done | vtophys() | |||
| if_lmc | Not done | Not done | Not done | Not done | vtophys() | |||
| if_lnc | David O'Brien | Not done | Not done | Not done | Not done | vtophys(). Please contact Poul-Henning Kamp for info/hardware. | ||
| if_mn | Not done | Not done | Not done | Not done | vtophys(). Please contact Poul-Henning Kamp for info/hardware. | |||
| if_my | Not done | Not done | Not done | Not done | vtophys() | |||
| if_nge | Not done | Not done | Not done | Not done | vtophys() | |||
| if_pcn | David O'Brien | Not done | Not done | Not done | Not done | vtophys() | ||
| if_pdq | Not done | Not done | Not done | Not done | mostly busdma, except for vtophys() | |||
| if_rl | Bill Paul | December 9, 2002 | Done | Not done | Not done | Not done | ||
| if_sf | Not done | Not done | Not done | Not done | vtophys() | |||
| if_sis | Bill Paul | December 9, 2002 | Done | Not done | Not done | Not done | ||
| if_sk | Not done | Not done | Not done | Not done | vtophys() | |||
| if_sr | Not done | Not done | Not done | Not done | vtophys() | |||
| if_ste | Not done | Not done | Not done | Not done | vtophys() | |||
| if_ti | Not done | Not done | Not done | Not done | ||||
| if_tl | Not done | Not done | Not done | Not done | ||||
| if_tx | Maxime Henrion | April 19, 2003 | Done | Not done | Not done | Needs testing | vtophys() | |
| if_txp | Will Andrews | July 18, 2003 | In progress | Not done | Not done | Not done | ||
| if_vr | Christian S.J. Peron <maneo@bsdpro.com> | January 20, 2003 | In progress | Not done | Not done | Not done | ||
| if_wb | Not done | Not done | Not done | Not done | ||||
| if_xl | Maxime Henrion | December 17, 2002 | Done | Not done | Not done | Done |
| Driver | Responsible | Last updated | busdma | INTR_MPSAFE | SMPng locked | a!=p | Notes |
|---|---|---|---|---|---|---|---|
| aac | Scott Long | February 8, 2003 | Done | Done | Done | Done | PCI-64 capable, not endian clean |
| adv | December 9, 2002 | Done | Not done | Not done | Not done | ||
| aha | December 9, 2002 | Done | Not done | Not done | Not done | ||
| ahb | December 9, 2002 | Done | Not done | Not done | Not done | ||
| aic7xxx | December 9, 2002 | Done | Not done | Not done | Not done | ||
| amd | December 14, 2002 | Done | Not done | Not done | Not done | ||
| amr | December 9, 2002 | Done | Not done | Not done | Not done | ||
| asr | David O'Brien | January 4, 2003 | Not done | Not done | Not done | Not done | vtophys() |
| ata | December 9, 2002 | Done | Not done | Not done | Done | ||
| buslogic | Not done | Not done | Not done | Not done | vtophys() | ||
| ciss | December 9, 2002 | Done | Not done | Not done | Not done | ||
| ct | Not done | Not done | Not done | Not done | |||
| dpt | Not done | Not done | Not done | Not done | vtophys() | ||
| ida | December 9, 2002 | Done | Not done | Not done | Not done | ||
| iir | Not done | Not done | Not done | Not done | vtophys() | ||
| isp | February 8, 2003 | Done | Done | Not done | Not done | ||
| mlx | Scott Long | February 8, 2003 | Done | In progress | In progress | Not done | |
| mly | Scott Long | February 8, 2003 | Done | In progress | In progress | Not done | |
| mpt | December 9, 2002 | Done | Done | Not done | Not done | ||
| ncr | Not done | Not done | Not done | Not done | vtophys(). Please contact Poul-Henning Kamp for a possible source of hardware. | ||
| pst | Not done | Not done | Not done | Not done | vtophys() | ||
| stg | December 9, 2002 | Done | Not done | Not done | Not done | At least, it looks like it may well be. | |
| sym | December 19, 2002 | Done | Not done | Not done | Not done | ||
| trm | Olivier Houchard | December 9, 2002 | Done | Not done | Not done | Not done | |
| twe | December 9, 2002 | Done | Not done | Not done | Not done |
| Driver | Responsible | Last updated | busdma | INTR_MPSAFE | SMPng locked | a!=p | Notes |
|---|---|---|---|---|---|---|---|
| agp | Olivier Houchard | January 23, 2003 | In progress | Not done | Not done | Not done | vtophys() |
| bktr | Olivier Houchard | January 15, 2003 | In progress | Not done | Not done | Not done | vtophys() |
| cs | Not done | Not done | Not done | Not done | |||
| digi | Not done | Not done | Not done | Not done | vtophys() | ||
| drm | Eric Anholt | February 17, 2003 | In progress | In progress | In progress | Not done | vtophys() |
| exca | Warner Losh | December 9, 2002 | Done | Not done | Not done | Not done | |
| fb | Not done | Not done | Not done | Not done | vtophys() | ||
| firewire | Hidetoshi Shimokawa | April 17, 2003 | Done | Not done | Not done | Done | vtophys() |
| hea | Not done | Not done | Not done | Not done | vtophys() | ||
| hfa | Not done | Not done | Not done | Not done | vtophys() | ||
| hifn | Sam Leffler | December 9, 2002 | Done | Not done | Not done | Not done | |
| meteor | Not done | Not done | Not done | Not done | vtophys() | ||
| musycc | Not done | Not done | Not done | Not done | vtophys(). Please contact Poul-Henning Kamp for info/hardware. | ||
| pcm | Olivier Houchard | February 20, 2003 | Done | Done | Not done | Not done | |
| ubsec | Sam Leffler | December 9, 2002 | Done | Not done | Not done | Not done | vtophys() is used in debugging printf |
| usb | John-Mark Gurney | July 24, 2003 | Done | Not done | Not done | Not done | a!=p should be clean, but requires further testing |
| wds | December 9, 2002 | Done | Not done | Not done | Not done |
| Task | Responsible | Last updated | Status | Notes |
|---|---|---|---|---|
| manpages for the busdma API | Hiten Pandya | January 15, 2003 | Done |