Add descriptors used in mikroBUS manifest #4
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mikroBUS addon boards allow using same mikroBUS connector for a wide range of peripherals. It is also possible for the addon board not to use all the pins in mikroBUS socket (marked by NC or Not Connected). This would require the need to create an almost new overlays for each permutation of the hardware. To overcome this, a manifest format based on Greybus manifest specification was created which allows describing mikroBUS addon boards. The reason for choosing greybus manifest for the identifier is that so far we discussed only about physical mikroBUS ports on the board, but we can also have mikroBUS ports on a remote microcontroller appearing on host over greybus (beagleconnect) and there a device tree overlay solution does not work as the standard identifier mechanism. New mikroBUS addon boards also sometimes contain a 1-wire EEPROM with the mikroBUS manifest, thus enabling plug and play support. There is ongoing work to get mikroBUS deriver merged in mainline linux kernel that used mikroBUS manifest for dynamic device identification. Link: https://www.mikroe.com/clickid ClickID Link: https://docs.beagleboard.org/latest/projects/beagleconnect/index.html beagleconnect Signed-off-by: Ayush Singh <ayushdevel1325@gmail.com>
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DONOTMERGE mikroBUS addon boards allow using same mikroBUS connector for a wide range of peripherals. It is also possible for the addon board not to use all the pins in mikroBUS socket (marked by NC or Not Connected). This would require the need to create an almost new overlays for each permutation of the hardware. To overcome this, a manifest format based on Greybus manifest specification was created which allows describing mikroBUS addon boards. The reason for choosing greybus manifest for the identifier is that so far we discussed only about physical mikroBUS ports on the board, but we can also have mikroBUS ports on a remote microcontroller appearing on host over greybus and there a device tree overlay solution does not work as the standard identifier mechanism. The patch introduces 3 new greybus descriptor types: 1. mikrobus-descriptor: Is a fixed-length descriptor (12 bytes), and the manifest shall have precisely one mikroBUS descriptor. Each byte describes a configuration of the corresponding pin on the mikroBUS addon board in a clockwise direction starting from the PWM pin omitting power (VCC and ground) pins as same as the default state of the pin. There are mikroBUS addon boards that use some dedicated SPI, UART, PWM, and I2C pins as GPIO pins, so it is necessary to redefine the default pin configuration of that pins on the host system. Also, sometimes it is required the pull-up on the host pin for correct functionality 2. property-descriptor: Are used to pass named properties or named GPIOs to the host. The host system uses this information to properly configure specific board drivers by passing the properties and GPIO name. There can be multiple instances of property descriptors per add-on board manifest. 3. device-descriptor: Describes a device on the mikroBUS port. The device descriptor is a fixed-length descriptor, and there can be multiple instances of device descriptors in an add-on board manifest in cases where the add-on board presents more than one device to the host. New mikroBUS addon boards also sometimes contain a 1-wire EEPROM with the mikroBUS manifest, thus enabling plug and play support. I have also created PR to add mikrobus descriptors in Greybus spec and I think the old PR on manifesto by Vaishnav should also work. However, both of these repositories seem to be inactive. I am guessing the greybus mailing list can provide more information on how I should go about these. Here is a sample mikroBUS manifest: ``` ;; ; PRESSURE CLICK ; https://www.mikroe.com/pressure-click ; CONFIG_IIO_ST_PRESS ; ; Copyright 2020 BeagleBoard.org Foundation ; Copyright 2020 Texas Instruments ; [manifest-header] version-major = 0 version-minor = 1 [interface-descriptor] vendor-string-id = 1 product-string-id = 2 [string-descriptor 1] string = MIKROE [string-descriptor 2] string = Pressure [mikrobus-descriptor] pwm-state = 4 int-state = 1 rx-state = 7 tx-state = 7 scl-state = 6 sda-state = 6 mosi-state = 5 miso-state = 5 sck-state = 5 cs-state = 5 rst-state = 2 an-state = 1 [device-descriptor 1] driver-string-id = 3 protocol = 0x3 reg = 0x5d [string-descriptor 3] string = lps331ap ``` Link: https://www.mikroe.com/clickid ClickID Link: https://docs.beagleboard.org/latest/projects/beagleconnect/index.html beagleconnect Link: https://github.com/projectara/greybus-spec Greybus Spec Link: projectara/greybus-spec#4 Greybus Spec PR Link: projectara/manifesto#2 manifesto PR Co-developed-by: Vaishnav M A <vaishnav@beagleboard.org> Signed-off-by: Vaishnav M A <vaishnav@beagleboard.org> Signed-off-by: Ayush Singh <ayushdevel1325@gmail.com>
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mikroBUS addon boards allow using same mikroBUS connector for a wide range of peripherals. It is also possible for the addon board not to use all the pins in mikroBUS socket (marked by NC or Not Connected). This would require the need to create an almost new overlays for each permutation of the hardware.
To overcome this, a manifest format based on Greybus manifest specification was created which allows describing mikroBUS addon boards. The reason for choosing greybus manifest for the identifier is that so far we discussed only about physical mikroBUS ports on the board, but we can also have mikroBUS ports on a remote microcontroller appearing on host over greybus (beagleconnect) and there a device tree overlay solution does not work as the standard identifier mechanism.
New mikroBUS addon boards also sometimes contain a 1-wire EEPROM with the mikroBUS manifest, thus enabling plug and play support.
There is ongoing work to get mikroBUS deriver merged in mainline linux kernel that used mikroBUS manifest for dynamic device identification.
Link: https://www.mikroe.com/clickid ClickID
Link:
https://docs.beagleboard.org/latest/projects/beagleconnect/index.html beagleconnect
Link: projectara/manifesto#2 manifesto support