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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/io-mapping.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/io-mapping.rst')
| -rw-r--r-- | Documentation/driver-api/io-mapping.rst | 91 |
1 files changed, 91 insertions, 0 deletions
diff --git a/Documentation/driver-api/io-mapping.rst b/Documentation/driver-api/io-mapping.rst new file mode 100644 index 000000000..7274204b0 --- /dev/null +++ b/Documentation/driver-api/io-mapping.rst @@ -0,0 +1,91 @@ +======================== +The io_mapping functions +======================== + +API +=== + +The io_mapping functions in linux/io-mapping.h provide an abstraction for +efficiently mapping small regions of an I/O device to the CPU. The initial +usage is to support the large graphics aperture on 32-bit processors where +ioremap_wc cannot be used to statically map the entire aperture to the CPU +as it would consume too much of the kernel address space. + +A mapping object is created during driver initialization using:: + + struct io_mapping *io_mapping_create_wc(unsigned long base, + unsigned long size) + +'base' is the bus address of the region to be made +mappable, while 'size' indicates how large a mapping region to +enable. Both are in bytes. + +This _wc variant provides a mapping which may only be used with +io_mapping_map_atomic_wc(), io_mapping_map_local_wc() or +io_mapping_map_wc(). + +With this mapping object, individual pages can be mapped either temporarily +or long term, depending on the requirements. Of course, temporary maps are +more efficient. They come in two flavours:: + + void *io_mapping_map_local_wc(struct io_mapping *mapping, + unsigned long offset) + + void *io_mapping_map_atomic_wc(struct io_mapping *mapping, + unsigned long offset) + +'offset' is the offset within the defined mapping region. Accessing +addresses beyond the region specified in the creation function yields +undefined results. Using an offset which is not page aligned yields an +undefined result. The return value points to a single page in CPU address +space. + +This _wc variant returns a write-combining map to the page and may only be +used with mappings created by io_mapping_create_wc() + +Temporary mappings are only valid in the context of the caller. The mapping +is not guaranteed to be globally visible. + +io_mapping_map_local_wc() has a side effect on X86 32bit as it disables +migration to make the mapping code work. No caller can rely on this side +effect. + +io_mapping_map_atomic_wc() has the side effect of disabling preemption and +pagefaults. Don't use in new code. Use io_mapping_map_local_wc() instead. + +Nested mappings need to be undone in reverse order because the mapping +code uses a stack for keeping track of them:: + + addr1 = io_mapping_map_local_wc(map1, offset1); + addr2 = io_mapping_map_local_wc(map2, offset2); + ... + io_mapping_unmap_local(addr2); + io_mapping_unmap_local(addr1); + +The mappings are released with:: + + void io_mapping_unmap_local(void *vaddr) + void io_mapping_unmap_atomic(void *vaddr) + +'vaddr' must be the value returned by the last io_mapping_map_local_wc() or +io_mapping_map_atomic_wc() call. This unmaps the specified mapping and +undoes the side effects of the mapping functions. + +If you need to sleep while holding a mapping, you can use the regular +variant, although this may be significantly slower:: + + void *io_mapping_map_wc(struct io_mapping *mapping, + unsigned long offset) + +This works like io_mapping_map_atomic/local_wc() except it has no side +effects and the pointer is globally visible. + +The mappings are released with:: + + void io_mapping_unmap(void *vaddr) + +Use for pages mapped with io_mapping_map_wc(). + +At driver close time, the io_mapping object must be freed:: + + void io_mapping_free(struct io_mapping *mapping) |
