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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2026-08-19 10:09:22 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2026-08-19 10:09:22 -0700 |
| commit | f4cdf7ca9a1fdcca413157df19753f388a5a224e (patch) | |
| tree | 60a31895b2446cd7fa27514e8c2843534a0de0da /Documentation/driver-api/vme.rst | |
| download | linux-stable-f4cdf7ca9a1fdcca413157df19753f388a5a224e.tar.gz linux-stable-f4cdf7ca9a1fdcca413157df19753f388a5a224e.zip | |
Merge tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-mediagrafted
Pull media updates from Mauro Carvalho Chehab:
- v4l2-core: added ISP statistics support and per-block validation
- v4l2-core: Allow unknown HDR10 white point and luminance
- New camera sensors: Sony IMX678 and IMX471m, Himax HM1092 IR sensor
- New codec: Milos: VPU v2.0 codec support
- isp driver: gained support for Dreamchip RPPX1 ISP framework
- vsp1 driver: gained support for RZ/T2H and RZ/N2H
- Novalake driver: gained CVS support for new NVL hardware
- dvb-core: fix feed leak on failed DMX_ADD_PID
- several driver fixes, cleanups and minor improvements
* tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (308 commits)
media: ipu-bridge: check all DMI entries when overriding sensor rotation
media: v4l2-async: avoid deleting unlinked ASC entry on link error
media: rzg2l-cru: Align bytesperline to hardware DMA stride requirement
media: intel/ipu6: fix async notifier cleanup leak on parse error
media: staging/ipu7: fix async notifier UAF on probe error path
media: amd: isp4: fix self-deadlock in isp4sd_pwron_and_init() error path
media: amd: isp4: release partial allocations in isp4if_alloc_fw_gpumem()
media: rcar-isp: Fix VSPX reference leaks
media: rcar-isp: Release ISPCORE resources
media: i2c: imx415: Release runtime PM reference on VBLANK error
media: i2c: imx415: Return test pattern write errors
media: renesas: vsp1: Declare index variables in for loop statement
media: renesas: vsp1: Make reset control optional to support platforms without a reset line
media: dt-bindings: media: renesas,vsp1: Document RZ/T2H and RZ/N2H SoCs
media: dt-bindings: media: renesas,fcp: Document RZ/T2H and RZ/N2H SoCs
media: nxp: imx8-isi: Add additional 32-bit RGB format support
media: nxp: imx8-isi: Add 16-bit raw Bayer format support
media: nxp: imx8-isi: Implement per-stream reference counting for multiplexed streams
media: nxp: imx8-isi: Use BIT_ULL() for 64-bit stream masks
media: nxp: imx8-isi: Correct color map between V4L2 and ISI
...
Diffstat (limited to 'Documentation/driver-api/vme.rst')
| -rw-r--r-- | Documentation/driver-api/vme.rst | 297 |
1 files changed, 297 insertions, 0 deletions
diff --git a/Documentation/driver-api/vme.rst b/Documentation/driver-api/vme.rst new file mode 100644 index 000000000..7111999ab --- /dev/null +++ b/Documentation/driver-api/vme.rst @@ -0,0 +1,297 @@ +VME Device Drivers +================== + +Driver registration +------------------- + +As with other subsystems within the Linux kernel, VME device drivers register +with the VME subsystem, typically called from the devices init routine. This is +achieved via a call to :c:func:`vme_register_driver`. + +A pointer to a structure of type :c:type:`struct vme_driver <vme_driver>` must +be provided to the registration function. Along with the maximum number of +devices your driver is able to support. + +At the minimum, the '.name', '.match' and '.probe' elements of +:c:type:`struct vme_driver <vme_driver>` should be correctly set. The '.name' +element is a pointer to a string holding the device driver's name. + +The '.match' function allows control over which VME devices should be registered +with the driver. The match function should return 1 if a device should be +probed and 0 otherwise. This example match function (from vme_user.c) limits +the number of devices probed to one: + +.. code-block:: c + + #define USER_BUS_MAX 1 + ... + static int vme_user_match(struct vme_dev *vdev) + { + if (vdev->id.num >= USER_BUS_MAX) + return 0; + return 1; + } + +The '.probe' element should contain a pointer to the probe routine. The +probe routine is passed a :c:type:`struct vme_dev <vme_dev>` pointer as an +argument. + +Here, the 'num' field refers to the sequential device ID for this specific +driver. The bridge number (or bus number) can be accessed using +dev->bridge->num. + +A function is also provided to unregister the driver from the VME core called +:c:func:`vme_unregister_driver` and should usually be called from the device +driver's exit routine. + + +Resource management +------------------- + +Once a driver has registered with the VME core the provided match routine will +be called the number of times specified during the registration. If a match +succeeds, a non-zero value should be returned. A zero return value indicates +failure. For all successful matches, the probe routine of the corresponding +driver is called. The probe routine is passed a pointer to the devices +device structure. This pointer should be saved, it will be required for +requesting VME resources. + +The driver can request ownership of one or more master windows +(:c:func:`vme_master_request`), slave windows (:c:func:`vme_slave_request`) +and/or dma channels (:c:func:`vme_dma_request`). Rather than allowing the device +driver to request a specific window or DMA channel (which may be used by a +different driver) the API allows a resource to be assigned based on the required +attributes of the driver in question. For slave windows these attributes are +split into the VME address spaces that need to be accessed in 'aspace' and VME +bus cycle types required in 'cycle'. Master windows add a further set of +attributes in 'width' specifying the required data transfer widths. These +attributes are defined as bitmasks and as such any combination of the +attributes can be requested for a single window, the core will assign a window +that meets the requirements, returning a pointer of type vme_resource that +should be used to identify the allocated resource when it is used. For DMA +controllers, the request function requires the potential direction of any +transfers to be provided in the route attributes. This is typically VME-to-MEM +and/or MEM-to-VME, though some hardware can support VME-to-VME and MEM-to-MEM +transfers as well as test pattern generation. If an unallocated window fitting +the requirements can not be found a NULL pointer will be returned. + +Functions are also provided to free window allocations once they are no longer +required. These functions (:c:func:`vme_master_free`, :c:func:`vme_slave_free` +and :c:func:`vme_dma_free`) should be passed the pointer to the resource +provided during resource allocation. + + +Master windows +-------------- + +Master windows provide access from the local processor[s] out onto the VME bus. +The number of windows available and the available access modes is dependent on +the underlying chipset. A window must be configured before it can be used. + + +Master window configuration +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Once a master window has been assigned :c:func:`vme_master_set` can be used to +configure it and :c:func:`vme_master_get` to retrieve the current settings. The +address spaces, transfer widths and cycle types are the same as described +under resource management, however some of the options are mutually exclusive. +For example, only one address space may be specified. + + +Master window access +~~~~~~~~~~~~~~~~~~~~ + +The function :c:func:`vme_master_read` can be used to read from and +:c:func:`vme_master_write` used to write to configured master windows. + +In addition to simple reads and writes, :c:func:`vme_master_rmw` is provided to +do a read-modify-write transaction. Parts of a VME window can also be mapped +into user space memory using :c:func:`vme_master_mmap_prepare`. + + +Slave windows +------------- + +Slave windows provide devices on the VME bus access into mapped portions of the +local memory. The number of windows available and the access modes that can be +used is dependent on the underlying chipset. A window must be configured before +it can be used. + + +Slave window configuration +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Once a slave window has been assigned :c:func:`vme_slave_set` can be used to +configure it and :c:func:`vme_slave_get` to retrieve the current settings. + +The address spaces, transfer widths and cycle types are the same as described +under resource management, however some of the options are mutually exclusive. +For example, only one address space may be specified. + + +Slave window buffer allocation +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Functions are provided to allow the user to allocate +(:c:func:`vme_alloc_consistent`) and free (:c:func:`vme_free_consistent`) +contiguous buffers which will be accessible by the VME bridge. These functions +do not have to be used, other methods can be used to allocate a buffer, though +care must be taken to ensure that they are contiguous and accessible by the VME +bridge. + + +Slave window access +~~~~~~~~~~~~~~~~~~~ + +Slave windows map local memory onto the VME bus, the standard methods for +accessing memory should be used. + + +DMA channels +------------ + +The VME DMA transfer provides the ability to run link-list DMA transfers. The +API introduces the concept of DMA lists. Each DMA list is a link-list which can +be passed to a DMA controller. Multiple lists can be created, extended, +executed, reused and destroyed. + + +List Management +~~~~~~~~~~~~~~~ + +The function :c:func:`vme_new_dma_list` is provided to create and +:c:func:`vme_dma_list_free` to destroy DMA lists. Execution of a list will not +automatically destroy the list, thus enabling a list to be reused for repetitive +tasks. + + +List Population +~~~~~~~~~~~~~~~ + +An item can be added to a list using :c:func:`vme_dma_list_add` (the source and +destination attributes need to be created before calling this function, this is +covered under "Transfer Attributes"). + +.. note:: + + The detailed attributes of the transfers source and destination + are not checked until an entry is added to a DMA list, the request + for a DMA channel purely checks the directions in which the + controller is expected to transfer data. As a result it is + possible for this call to return an error, for example if the + source or destination is in an unsupported VME address space. + +Transfer Attributes +~~~~~~~~~~~~~~~~~~~ + +The attributes for the source and destination are handled separately from adding +an item to a list. This is due to the diverse attributes required for each type +of source and destination. There are functions to create attributes for PCI, VME +and pattern sources and destinations (where appropriate): + + - PCI source or destination: :c:func:`vme_dma_pci_attribute` + - VME source or destination: :c:func:`vme_dma_vme_attribute` + - Pattern source: :c:func:`vme_dma_pattern_attribute` + +The function :c:func:`vme_dma_free_attribute` should be used to free an +attribute. + + +List Execution +~~~~~~~~~~~~~~ + +The function :c:func:`vme_dma_list_exec` queues a list for execution and will +return once the list has been executed. + + +Interrupts +---------- + +The VME API provides functions to attach and detach callbacks to specific VME +level and status ID combinations and for the generation of VME interrupts with +specific VME level and status IDs. + + +Attaching Interrupt Handlers +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The function :c:func:`vme_irq_request` can be used to attach and +:c:func:`vme_irq_free` to free a specific VME level and status ID combination. +Any given combination can only be assigned a single callback function. A void +pointer parameter is provided, the value of which is passed to the callback +function, the use of this pointer is user undefined. The callback parameters are +as follows. Care must be taken in writing a callback function, callback +functions run in interrupt context: + +.. code-block:: c + + void callback(int level, int statid, void *priv); + + +Interrupt Generation +~~~~~~~~~~~~~~~~~~~~ + +The function :c:func:`vme_irq_generate` can be used to generate a VME interrupt +at a given VME level and VME status ID. + + +Location monitors +----------------- + +The VME API provides the following functionality to configure the location +monitor. + + +Location Monitor Management +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The function :c:func:`vme_lm_request` is provided to request the use of a block +of location monitors and :c:func:`vme_lm_free` to free them after they are no +longer required. Each block may provide a number of location monitors, +monitoring adjacent locations. The function :c:func:`vme_lm_count` can be used +to determine how many locations are provided. + + +Location Monitor Configuration +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Once a bank of location monitors has been allocated, the function +:c:func:`vme_lm_set` is provided to configure the location and mode of the +location monitor. The function :c:func:`vme_lm_get` can be used to retrieve +existing settings. + + +Location Monitor Use +~~~~~~~~~~~~~~~~~~~~ + +The function :c:func:`vme_lm_attach` enables a callback to be attached and +:c:func:`vme_lm_detach` allows on to be detached from each location monitor +location. Each location monitor can monitor a number of adjacent locations. The +callback function is declared as follows. + +.. code-block:: c + + void callback(void *data); + + +Slot Detection +-------------- + +The function :c:func:`vme_slot_num` returns the slot ID of the provided bridge. + + +Bus Detection +------------- + +The function :c:func:`vme_bus_num` returns the bus ID of the provided bridge. + + +VME API +------- + +.. kernel-doc:: drivers/staging/vme_user/vme.h + :internal: + +.. kernel-doc:: drivers/staging/vme_user/vme.c + :export: |
