Question about UIO vs DT

Question about UIO vs DT

[Kuninori Morimoto]

Hi Greg / UIO / DT

I would like to ask about UIO vs DT.

If my understanding was correct, current UIO can use 1 IRQ / 1 reg per 1 UIO,
but some device needs multi-IRQ/reg. In such case, we need to use
multi-UIO. But it is not good much to DT rule. For example in case of
the device which needs "2 regs 3 irqs". it will be

(A)	[1 reg, 1 IRQ] UIO
(B)	[1 reg, 1 IRQ] UIO
(C)	[0 reg, 1 IRQ] UIO

and (C) will be DT error. Is this known issue ? Do we have better solution ?

Thank you for your help !!

Best regards
---
Kuninori Morimoto

Re: Question about UIO vs DT

[Greg KH]

On Thu, May 15, 2025 at 04:45:23AM +0000, Kuninori Morimoto wrote:
> 
> Hi Greg / UIO / DT
> 
> I would like to ask about UIO vs DT.
> 
> If my understanding was correct, current UIO can use 1 IRQ / 1 reg per 1 UIO,
> but some device needs multi-IRQ/reg. In such case, we need to use
> multi-UIO. But it is not good much to DT rule. For example in case of
> the device which needs "2 regs 3 irqs". it will be
> 
> (A)	[1 reg, 1 IRQ] UIO
> (B)	[1 reg, 1 IRQ] UIO
> (C)	[0 reg, 1 IRQ] UIO
> 
> and (C) will be DT error. Is this known issue ? Do we have better solution ?

Yes, write a real driver for the device as obviously it is a complex one
and UIO shouldn't be used for it :)

What type of device is this that requires this type of hardware control
and why do you feel that UIO is the proper solution?

thanks,

greg k-h

Re: Question about UIO vs DT

[Kuninori Morimoto]

Hi Greg

Thank you for the reply

> > For example in case of
> > the device which needs "2 regs 3 irqs". it will be
> > 
> > (A)	[1 reg, 1 IRQ] UIO
> > (B)	[1 reg, 1 IRQ] UIO
> > (C)	[0 reg, 1 IRQ] UIO
> > 
> > and (C) will be DT error. Is this known issue ? Do we have better solution ?
> 
> Yes, write a real driver for the device as obviously it is a complex one
> and UIO shouldn't be used for it :)
> 
> What type of device is this that requires this type of hardware control
> and why do you feel that UIO is the proper solution?

One of big reason is license.
Because it needs to be proprietary licensed driver, we can't create
real driver.

Our team is thinking it will be no more DT error if UIO can allow
below, somehow.

	reg = <reg1 reg2>;
	interrupts = <irq1 irq2 irq3>;

Thank you for your help !!

Best regards
---
Kuninori Morimoto

Re: Question about UIO vs DT

[Greg KH]

On Fri, May 16, 2025 at 02:18:07AM +0000, Kuninori Morimoto wrote:
> 
> Hi Greg
> 
> Thank you for the reply
> 
> > > For example in case of
> > > the device which needs "2 regs 3 irqs". it will be
> > > 
> > > (A)	[1 reg, 1 IRQ] UIO
> > > (B)	[1 reg, 1 IRQ] UIO
> > > (C)	[0 reg, 1 IRQ] UIO
> > > 
> > > and (C) will be DT error. Is this known issue ? Do we have better solution ?
> > 
> > Yes, write a real driver for the device as obviously it is a complex one
> > and UIO shouldn't be used for it :)
> > 
> > What type of device is this that requires this type of hardware control
> > and why do you feel that UIO is the proper solution?
> 
> One of big reason is license.
> Because it needs to be proprietary licensed driver, we can't create
> real driver.

That is not a valid reason at all, sorry.  So much so that I, and many
others, have argued that you can not have UIO drivers in userspace that
are NOT also released under the GPLv2.

Go work with your lawyers please, there's nothing I can now do to help
you out with this due to the expectation that you are attempting to
evade the license requirements here.

greg k-h

Re: Question about UIO vs DT

[Kuninori Morimoto]

Hi Greg

Thank you for your help

> > > > (A)	[1 reg, 1 IRQ] UIO
> > > > (B)	[1 reg, 1 IRQ] UIO
> > > > (C)	[0 reg, 1 IRQ] UIO
> > > > 
> > > > and (C) will be DT error. Is this known issue ? Do we have better solution ?
> > > 
> > > Yes, write a real driver for the device as obviously it is a complex one
> > > and UIO shouldn't be used for it :)
> > > 
> > > What type of device is this that requires this type of hardware control
> > > and why do you feel that UIO is the proper solution?
> > 
> > One of big reason is license.
> > Because it needs to be proprietary licensed driver, we can't create
> > real driver.
> 
> That is not a valid reason at all, sorry.  So much so that I, and many
> others, have argued that you can not have UIO drivers in userspace that
> are NOT also released under the GPLv2.
> 
> Go work with your lawyers please, there's nothing I can now do to help
> you out with this due to the expectation that you are attempting to
> evade the license requirements here.

OK, Thank you for clearing details and helping us.
I will forward this info to the relatead members.

Thank you for your help !!

Best regards
---
Kuninori Morimoto