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author | Linus Torvalds <torvalds@linux-foundation.org> | 2023-09-01 12:21:32 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2023-09-01 12:21:32 -0700 |
commit | 307d59039fb26212a84a9aa6a134a7d2bdea34ca (patch) | |
tree | dca021901b6e13b04bd4ab1671d28081a80016d9 /Documentation/i2c | |
parent | b84acc11b1c9552c9ca3a099b1610a6018619332 (diff) | |
parent | 9a5d660fdb25d20748d7f9e9559c86073c3bb368 (diff) | |
download | linux-307d59039fb26212a84a9aa6a134a7d2bdea34ca.tar.gz linux-307d59039fb26212a84a9aa6a134a7d2bdea34ca.tar.bz2 linux-307d59039fb26212a84a9aa6a134a7d2bdea34ca.zip |
Merge tag 'media/v6.6-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media
Pull media updates from Mauro Carvalho Chehab:
- new i2c drivers: ds90ub913, ds90ub953, ds90ub960, dw9719, ds90ub913
- new Intel IVSC MEI drivers
- some Mediatek platform drivers were moved to a common location
- Intel atomisp2 driver is now working with the main ov2680 driver. Due
to that, the atomisp2 ov2680 staging one was removed
- the bttv driver was finally converted to videobuf2 framework. This
was the last one upstream using videobuf version 1 core. We'll likely
remove the old videobuf framework on 6.7
- lots of improvements at atomisp driver: it now works with normal I2C
sensors. Several compile-mode dependecies to select between ISP2400
and ISP2401 are now solved in runtime
- a new ipu-bridge logic was added to work with IVSC MEI drivers
- venus driver gained better support for new VPU versions
- the v4l core async framework has gained lots of improvements and
cleanups
- lots of other cleanups, improvements and driver fixes
* tag 'media/v6.6-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (358 commits)
media: ivsc: Add ACPI dependency
media: bttv: convert to vb2
media: bttv: use audio defaults for winfast2000
media: bttv: refactor bttv_set_dma()
media: bttv: move vbi_skip/vbi_count out of buffer
media: bttv: remove crop info from bttv_buffer
media: bttv: remove tvnorm field from bttv_buffer
media: bttv: remove format field from bttv_buffer
media: bttv: move do_crop flag out of bttv_fh
media: bttv: copy vbi_fmt from bttv_fh
media: bttv: copy vid fmt/width/height from fh
media: bttv: radio use v4l2_fh instead of bttv_fh
media: bttv: replace BUG with WARN_ON
media: bttv: use video_drvdata to get bttv
media: i2c: rdacm21: Fix uninitialized value
media: coda: Remove duplicated include
media: vivid: fix the racy dev->radio_tx_rds_owner
media: i2c: ccs: Check rules is non-NULL
media: i2c: ds90ub960: Fix PLL config for 1200 MHz CSI rate
media: i2c: ds90ub953: Fix use of uninitialized variables
...
Diffstat (limited to 'Documentation/i2c')
-rw-r--r-- | Documentation/i2c/i2c-address-translators.rst | 96 | ||||
-rw-r--r-- | Documentation/i2c/index.rst | 1 |
2 files changed, 97 insertions, 0 deletions
diff --git a/Documentation/i2c/i2c-address-translators.rst b/Documentation/i2c/i2c-address-translators.rst new file mode 100644 index 000000000000..b22ce9f41ecf --- /dev/null +++ b/Documentation/i2c/i2c-address-translators.rst @@ -0,0 +1,96 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================= +I2C Address Translators +======================= + +Author: Luca Ceresoli <luca@lucaceresoli.net> +Author: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> + +Description +----------- + +An I2C Address Translator (ATR) is a device with an I2C slave parent +("upstream") port and N I2C master child ("downstream") ports, and +forwards transactions from upstream to the appropriate downstream port +with a modified slave address. The address used on the parent bus is +called the "alias" and is (potentially) different from the physical +slave address of the child bus. Address translation is done by the +hardware. + +An ATR looks similar to an i2c-mux except: + - the address on the parent and child busses can be different + - there is normally no need to select the child port; the alias used on the + parent bus implies it + +The ATR functionality can be provided by a chip with many other features. +The kernel i2c-atr provides a helper to implement an ATR within a driver. + +The ATR creates a new I2C "child" adapter on each child bus. Adding +devices on the child bus ends up in invoking the driver code to select +an available alias. Maintaining an appropriate pool of available aliases +and picking one for each new device is up to the driver implementer. The +ATR maintains a table of currently assigned alias and uses it to modify +all I2C transactions directed to devices on the child buses. + +A typical example follows. + +Topology:: + + Slave X @ 0x10 + .-----. | + .-----. | |---+---- B + | CPU |--A--| ATR | + `-----' | |---+---- C + `-----' | + Slave Y @ 0x10 + +Alias table: + +A, B and C are three physical I2C busses, electrically independent from +each other. The ATR receives the transactions initiated on bus A and +propagates them on bus B or bus C or none depending on the device address +in the transaction and based on the alias table. + +Alias table: + +.. table:: + + =============== ===== + Client Alias + =============== ===== + X (bus B, 0x10) 0x20 + Y (bus C, 0x10) 0x30 + =============== ===== + +Transaction: + + - Slave X driver requests a transaction (on adapter B), slave address 0x10 + - ATR driver finds slave X is on bus B and has alias 0x20, rewrites + messages with address 0x20, forwards to adapter A + - Physical I2C transaction on bus A, slave address 0x20 + - ATR chip detects transaction on address 0x20, finds it in table, + propagates transaction on bus B with address translated to 0x10, + keeps clock streched on bus A waiting for reply + - Slave X chip (on bus B) detects transaction at its own physical + address 0x10 and replies normally + - ATR chip stops clock stretching and forwards reply on bus A, + with address translated back to 0x20 + - ATR driver receives the reply, rewrites messages with address 0x10 + as they were initially + - Slave X driver gets back the msgs[], with reply and address 0x10 + +Usage: + + 1. In the driver (typically in the probe function) add an ATR by + calling i2c_atr_new() passing attach/detach callbacks + 2. When the attach callback is called pick an appropriate alias, + configure it in the chip and return the chosen alias in the + alias_id parameter + 3. When the detach callback is called, deconfigure the alias from + the chip and put the alias back in the pool for later usage + +I2C ATR functions and data structures +------------------------------------- + +.. kernel-doc:: include/linux/i2c-atr.h diff --git a/Documentation/i2c/index.rst b/Documentation/i2c/index.rst index 6270f1fd7d4e..2b213d4ce89c 100644 --- a/Documentation/i2c/index.rst +++ b/Documentation/i2c/index.rst @@ -18,6 +18,7 @@ Introduction i2c-topology muxes/i2c-mux-gpio i2c-sysfs + i2c-address-translators Writing device drivers ====================== |