Messages in this thread | | | Subject | Re: [PATCH v10 0/9] Add the I3C subsystem | From | vitor <> | Date | Thu, 15 Nov 2018 15:18:21 +0000 |
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Hi,
On 15/11/18 12:57, Boris Brezillon wrote: > +Mark Brown for the question about /dev/spidev > > Hi Vitor, > > On Thu, 15 Nov 2018 12:14:37 +0000 > vitor <vitor.soares@synopsys.com> wrote: > >> Hi Boris, >> >> Given the current state of the subsystem I think it might worth start to >> think how to expose the devices under /dev. > Thanks for starting this discussion. I'm not against the idea in > general, we just need to be careful when doing that. > >> My initial thoughts are to do the same think as for i2c, expose the >> buses or the i3c_devices and use ioctl for private transfers. > Exposing the bus is dangerous IMO, because an I3C bus is not like an > I2C bus: > > * I3C device needs to be discovered through DAA > * I2C devices need to be declared ahead of time, and LVR is used to > determine the limitations on the bus at runtime > > So you'd anyway be able to interact only with devices that have > previously been discovered. > > Note that the virtual I2C bus is already exposed, but any command > targeting an address that is not attached to a registered I2C dev will > get a -ENOENT error. I initially thought to do the same thing for the i3c devices adding a routine get_i3c_dev_by_addr()... > > What we could do though, is expose I3C devices that do not have a > driver in kernel space, like spidev does.
...but I like more this approach.
>> Some >> direct CCC commands can be sent through the /sys as you plan for SETNEWDA . > Yes, CCC commands that need to be exposed to userspace should be > exposed through sysfs, or, if we decide to create a /dev/i3cX device > per bus, through ioctls.
There already some attributes exposed, just need to add the possibility to write to them and off course add some that are missing like GETSTATUS.
> >> What do you think about this? > I think this request is perfectly valid, we just need to decide how it > should be done, and before we take this decision, I'd like to get > inputs from other maintainers. > > Mark, Wolfram, Arnd, Greg, any opinion? > > Regards, > > Boris
Best regards,
Vitor Soares
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