[PATCH v3 0/5] Introduce i3c device userspace interface

From: Vitor Soares
Date: Tue Feb 18 2020 - 19:20:52 EST


For today there is no way to use i3c devices from user space and
the introduction of such API will help developers during the i3c device
or i3c host controllers development.

The i3cdev module is highly based on i2c-dev and yet I tried to address
the concerns raised in [1].

NOTES:
- The i3cdev dynamically request an unused major number.

- The i3c devices are dynamically exposed/removed from dev/ folder based
on if they have a device driver bound to it.

- For now, the module exposes i3c devices without device driver on
dev/bus/i3c/<bus>-<pid>

- As in the i2c subsystem, here it is exposed the i3c_priv_xfer to
userspace. I tried to use a dedicated structure as in spidev but I don't
see any obvious advantage.

- Since the i3c API only exposes i3c_priv_xfer to devices, for now, the
module just makes use of one ioctl(). This can change in the future with
the introduction hdr commands or by the need of exposing some CCC
commands to the device API (private contract between master-slave).
Regarding the i3c device info, some information is already available
through sysfs. We can add more device attributes to expose more
information or add a dedicated ioctl() request for that purpose or both.

- Similar to i2c, I have also created a tool that you can find in [2]
for testing purposes. If you have some time available I would appreciate
your feedback about it as well.

[1] https://lkml.org/lkml/2018/11/15/853
[2] https://github.com/vitor-soares-snps/i3c-tools.git

Changes in v3:
Use the xfer_lock to prevent device detach during ioctl call
Expose i3cdev under /dev/bus/i3c/ folder like usb does
Change NOTIFY_BOUND to NOTIFY_BIND, this allows the device detach occur
before driver->probe call
Avoid use of IS_ERR_OR_NULL
Use u64_to_user_ptr instead of (void __user *)(uintptr_t) cast
Allocate k_xfer and data_ptrs at once and eliminate double allocation
check
Pass i3cdev to dev->driver_data
Make all minors available
Add API documentation

Changes in v2:
Use IDR api for minor numbering
Modify ioctl struct
Fix SPDX license

Vitor Soares (5):
i3c: master: export i3c_masterdev_type
i3c: master: export i3c_bus_type symbol
i3c: master: add i3c_for_each_dev helper
i3c: add i3cdev module to expose i3c dev in /dev
Documentation: userspac-api: add i3cdev documentation

Documentation/userspace-api/i3c/i3cdev.rst | 116 ++++++++
drivers/i3c/Kconfig | 15 +
drivers/i3c/Makefile | 1 +
drivers/i3c/i3cdev.c | 429 +++++++++++++++++++++++++++++
drivers/i3c/internals.h | 2 +
drivers/i3c/master.c | 16 +-
include/uapi/linux/i3c/i3cdev.h | 38 +++
7 files changed, 616 insertions(+), 1 deletion(-)
create mode 100644 Documentation/userspace-api/i3c/i3cdev.rst
create mode 100644 drivers/i3c/i3cdev.c
create mode 100644 include/uapi/linux/i3c/i3cdev.h

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