Hi Russell,
I had originally worked on this and will try to provide some more context which is missing in this series. I am replying from my TI email as I am active here.
On 16/03/24 02:49, Russell King (Oracle) wrote:
On Sat, Mar 16, 2024 at 02:17:24AM +0530, Ayush Singh wrote:
On 3/16/24 01:02, Russell King (Oracle) wrote:
On Sat, Mar 16, 2024 at 12:19:05AM +0530, Ayush Singh wrote:
diff --git a/drivers/misc/mikrobus/Kconfig b/drivers/misc/mikrobus/Kconfig new file mode 100644 index 000000000000..f0770006b4fe --- /dev/null +++ b/drivers/misc/mikrobus/Kconfig @@ -0,0 +1,19 @@ +menuconfig MIKROBUS
- tristate "Module for instantiating devices on mikroBUS ports"
- depends on GPIOLIB
- depends on W1
- depends on W1_MASTER_GPIO
- help
This option enables the mikroBUS driver. mikroBUS is an add-onboard socket standard that offers maximum expandability withthe smallest number of pins. The mikroBUS driver instantiatesdevices on a mikroBUS port described by identifying data presentin an add-on board resident EEPROM, more details on the mikroBUSdriver support and discussion can be found in this eLinux wiki :elinux.org/MikrobusI think this is a fallacy. I have boards that support Mikrobus - some of the SolidRun products do. I have several Mikrobus "click" boards.
This help text seems to imply that Mikrobus click boards include an EEPROM that identify them, hence you make the support for mikroBUS depend on it. No, this is not the case - the click boards do not contain a 1-wire EEPROM.
Please fetch a copy of the official Mikrobus specification which is available here:
https://download.mikroe.com/documents/standards/mikrobus/mikrobus-standard-s...
and rather than creating something that is implementation specific but appears to be generic, create something that is generic with implementation specific extensions.
I think you mean mikroBUS addon boards? mikroBUS is an open socket and click boards™ are MikroElektronika’s brand of mikroBUS™ add-on boards.
MikroElektronika _owns_ the standard for mikroBUS, they're the ones who publish it and it has their logo plastered all over it.
Yes, MikroE owns the standard but they do not prevent anyone from creating new add-on boards or adding the sockets in commercially available boards, with the only condition that custom mikroBUS add-on boards cannot be marketed with the name "click" board.
So I think all click boards™ do have clickID support, but yes, mikroBUS spec is not the same as clickID and thus are not mutually dependent.
None of the MikroElektronika "click" boards that I have (and thus officially produced boards) have any ID EEPROM on them, so your statement is false. For example, if you look at the "relay click" board schematic:
https://download.mikroe.com/documents/add-on-boards/click/relay/relay-click-...
you will find no EEPROM.
The "relay 3" click board also doesn't:
https://download.mikroe.com/documents/add-on-boards/click/relay-3/relay-3-sc...
However, the "relay 4" click board does:
https://download.mikroe.com/documents/add-on-boards/click/relay_4_click/Rela...
Now, ClickID is relatively new. Note that the mikroBUS standard dates from 2011, with v2 coming out in 2015. A blog post introducing ClickID was posted in November 2023, just some 5 months ago, so that leaves an awful lot of click boards out there at the moment which have no EEPROM on them.
If what you have written assumes that all click boards have this EEPROM then you are - in my opinion - intolerably constraining the usefulness of your idea for those of us who have click boards bought over the past few years, and this will confuse users who have these older boards. "I've enabled mikroBUS support in the kernel, but my board isn't recognised" will probably end up being a regular cry from people with this.
So, I think you need to consider how to support the already vast number of click boards that do not support ClickID.
The same series actually can support mikroBUS add-on boards without EEPROM as well, it exposes a sysfs interface similar to i2c new_device, so all you need to do is to plug-in the add-on board, the pass the manifest using this interface. Example : cat /lib/firmware/mikrobus/AMBIENT-2-CLICK.mnfb > /sys/bus/mikrobus/devices/mikrobus-0/new_device
Reference: https://docs.beagleboard.org/latest/boards/beagleplay/demos-and-tutorials/us...
I am not sure if passing binary manifest blob using the sysfs interface is an ideal solution, but the driver can support boards without EEPROM. Actually the 150+ boards we have validated in the past did not have EEPROM on all of them : https://github.com/MikroElektronika/click_id/tree/main/manifests
At the moment, my own personal solution is currently to hack the platform's DT file for the board I wish to use, creating a new variant of the platform which configures the SoC so the mikroBUS connector pins are appropriately configured. It would be good to get away from the need to do that.
Yes, the pain point with creating device tree overlays for mikroBUS add-on boards is that you need an almost new overlays for each permutation of the hardware (150+ add-on boards with driver support in Linux connected on just BeagleBoard platforms like BeaglePlay[1 port], PocketBeagle [2 port], mikroBUS cape on BB black[4 ports]) is more than 1000 overlays to maintain, this driver aims to split the platform aspects of mikroBUS (pinmux, SPI/I2C/GPIO controller .etc) from the add-on board information, thus requiring one device tree overlay per port and just a single manifest describing the add-on board.
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 is greybus manifest, some details on the remote greybus mikrobus port is available here:
https://docs.beagleboard.org/boards/beagleconnect/technology/index.html
Here is an old video of the concept working: https://www.youtube.com/watch?v=JKrCRRuCw3c
To summarise, the driver with proper fixes and feedback incorporated can support mikroBUS Click ID boards(plug and play), existing mikroBUS add-on boards (with a clean way to pass the manifest to driver, slight manual intervention compared to click ID boards) and also mikroBUS add-on board connected to a remote microcontroller appearing over greybus (not part of the series, but mentioning it so that it is clear why greybus manifest is chosen as the descriptor format).
Thanks and Regards, Vaishnav