Re: [PATCH v1 04/29] xen/asm-generic: introduce stub header device.h

[Julien Grall <julien@xxxxxxx>]

Hi,

On 19/10/2023 10:14, Jan Beulich wrote:
> On 14.09.2023 16:56, Oleksii Kurochko wrote:
> > --- /dev/null
> > +++ b/xen/include/asm-generic/device.h
> > @@ -0,0 +1,65 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +#ifndef __ASM_GENERIC_DEVICE_H__
> > +#define __ASM_GENERIC_DEVICE_H__
> > +
> > +struct dt_device_node;
> > +
> > +enum device_type
> > +{
> > +    DEV_DT,
> > +    DEV_PCI,
> > +};
> Are both of these really generic?
I think can be re-used for RISC-V to have an abstract view a device. 
This is for instance used in the IOMMU code where both PCI and platform 
(here called DT) can be assigned to a domain. The driver will need to 
know the difference, but the common layer doesn't need to.
> > +struct device {
> > +    enum device_type type;
> > +#ifdef CONFIG_HAS_DEVICE_TREE
> > +    struct dt_device_node *of_node; /* Used by drivers imported from Linux */
> > +#endif
> > +};
> > +
> > +enum device_class
> > +{
> > +    DEVICE_SERIAL,
> > +    DEVICE_IOMMU,
> > +    DEVICE_GIC,
> This one certainly is Arm-specific.
This could be renamed to DEVICE_IC (or INTERRUPT_CONTROLLER)

> > +    DEVICE_PCI_HOSTBRIDGE,
> And this one's PCI-specific.
Are you suggesting to #ifdef it? If so, I don't exactly see the value here.

> Overall same question as before: Are you expecting that RISC-V is going to
> get away without a customized header? I wouldn't think so.
I think it can be useful. Most likely you will have multiple drivers for 
a class and you may want to initialize certain device class early than 
others. See how it is used in device_init().
Cheers,

--
Julien Grall