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Message-ID: <CH2PR12MB421604E9272413A6C456AB16AE100@CH2PR12MB4216.namprd12.prod.outlook.com>
Date: Wed, 19 Feb 2020 00:39:31 +0000
From: Vitor Soares <Vitor.Soares@...opsys.com>
To: "bbrezillon@...nel.org" <bbrezillon@...nel.org>
CC: Joao Pinto <Joao.Pinto@...opsys.com>,
Jose Abreu <Jose.Abreu@...opsys.com>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"wsa@...-dreams.de" <wsa@...-dreams.de>,
"arnd@...db.de" <arnd@...db.de>,
"broonie@...nel.org" <broonie@...nel.org>,
"corbet@....net" <corbet@....net>,
Vitor Soares <Vitor.Soares@...opsys.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-i3c@...ts.infradead.org" <linux-i3c@...ts.infradead.org>
Subject: RE: [PATCH v3 0/5] Introduce i3c device userspace interface
Hi Boris,
From: Vitor Soares <vitor.soares@...opsys.com>
Date: Wed, Feb 19, 2020 at 00:20:38
> 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
> userspace-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
>
> --
> 2.7.4
I want to make you know that none of your previous comments was ignored
and I would like to start the discussion from this point.
Best regards,
Vitor Soares
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