[RFC 0/2]convert ACPI driver model to Linux driver model

[RFC 0/2]convert ACPI driver model to Linux driver model

[Shaohua Li]

Hi,
I'm sending the patches out not for merging but for comments. The
patches try to convert ACPI driver model to Linux driver model. There
are still many things unsettled. If you have any
comment/suggestion/requirement, please let me know.

1. in my mind, acpi should export two sets of info in sysfs. One is
current namespace subsystem, it should just export the firmware info.
All acpi device/drivers related info don't export here. The other is
ACPI bus. It's similar with other buses like PCI bus.

2. I regard all devices which don't belong to physical buses in the DSDT
as ACPI bus devices. Ideally, PCI devices, PNP devices & other devices
should bind them to their physical buses. Since many devices listed in
DSDT aren't in ACPI bus, this makes it impossible to convert current
acpi driver model into Linux style. You might look at my patch, many
routines required by Linux driver model are empty. Though we can't
completely utilize the advantage of Linux driver model, the partial
convert still benefits us many such as sysfs support and suspend/resume
support.

3. The acpi namespace hotplug interface looks strange. After we
introduce ACPI bus (CPU is in the bus), we can send hotplug event
through it. So I'd like to remove the namespace hotplug interface later.

There are something to prevent us from completely converting ACPI driver
model to Linux style:
1. Current ACPI driver model can register drivers for all devices listed
in DSDT. ACPI bus can't handle this.
2. Current ACPI hotplug (CPU/IO) relays on separate .add/.start
callbacks, but Linux driver can only provide a .probe. We might split
ACPI hotplug support to separate drivers.
Since these, my patch just adds fake Linux driver model support, but it
still is very useful.

Thanks,
Shaohua



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Re: [RFC 0/2]convert ACPI driver model to Linux driver model

[Dominik Brodowski]

Hi,

On Mon, Sep 12, 2005 at 01:22:22PM +0800, Shaohua Li wrote:
> I'm sending the patches out not for merging but for comments. The
> patches try to convert ACPI driver model to Linux driver model. 

Excellent.

> 1. in my mind, acpi should export two sets of info in sysfs. One is
> current namespace subsystem, it should just export the firmware info.
> All acpi device/drivers related info don't export here. The other is
> ACPI bus. It's similar with other buses like PCI bus.

However, there is no physical ACPI bus. Therefore, it shouldn't exist in
/sys/devices/ or /sys/bus/. If they are platform devices (devices which can be
poked at some iomem or ioport address, but aren't on any specific bus), they
should be registered as platform devices; if these are system devices
(core devices for basic operation; can live with IRQs off for suspend and 
resume, or even require that) they should be registered as system devices.

> 2. I regard all devices which don't belong to physical buses in the DSDT
> as ACPI bus devices. Ideally, PCI devices, PNP devices & other devices
> should bind them to their physical buses.

Yes, exactly.

> Since many devices listed in
> DSDT aren't in ACPI bus, this makes it impossible to convert current
> acpi driver model into Linux style.

Indeed. For each device, you need to decide which bus it resides on:
> (CPU is in the bus)

No, CPUs are already registered as system devices. ( /sys/devices/system/cpu/ )
Don't insert them twice into the device tree, please

>  So I'd like to remove the namespace hotplug interface later.
Indeed, let's focus on this stuff later on.

So, let's look at the devices and where they should be registered. In most
cases, it is just a guess on my side; system devices are suspended and
resumed with interrupts off; that most probably should be a decisive point
in this distinction.

+       "PNP0C09", /* EC */
-> system or platform, not sure...

+       "ACPI0003", /* AC */
-> platform

+       "PNP0C0F", /* Link */
-> system. Might this already be registered on some systems? I have
irqrouter, i8237 and i8259 in /sys/devices/system/

+       "PNP0C0A", /* battery */
-> platform

+       "PNP0C0C", "PNP0C0E", "PNP0C0D", "ACPI_FPB" ,"ACPI_FSB", /* button */
-> platform

+       "PNP0C0B", /* fan */
-> platform

+       "PNP0A03", /* PCI root */
-> system or platform, not sure either.... Please make sure that "pci0000:00" or
   whatever is registered as a child of this device.

+       ACPI_POWER_HID, /* power */
-> platform

+       ACPI_PROCESSOR_HID, /* CPU */
-> system, is already there...

+       ACPI_THERMAL_HID, /* thermal */
-> platform


Also, you might think about adding all these devices to "class ACPI".
/sys/class/acpi/ is perfectly valid; there you can add some common
infrastrucutre for _all_ ACPI-enumerated devices, rely on "class interface"
and other methods available.

Thanks,
	Dominik


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Re: [RFC 0/2]convert ACPI driver model to Linux driver model

[Shaohua Li]

On Mon, 2005-09-12 at 19:57 +0200, Dominik Brodowski wrote:
> Hi,
> 
> On Mon, Sep 12, 2005 at 01:22:22PM +0800, Shaohua Li wrote:
> > I'm sending the patches out not for merging but for comments. The
> > patches try to convert ACPI driver model to Linux driver model. 
Thanks for your time.

> > 1. in my mind, acpi should export two sets of info in sysfs. One is
> > current namespace subsystem, it should just export the firmware info.
> > All acpi device/drivers related info don't export here. The other is
> > ACPI bus. It's similar with other buses like PCI bus.
> 
> However, there is no physical ACPI bus. Therefore, it shouldn't exist in
> /sys/devices/ or /sys/bus/. If they are platform devices (devices which can be
> poked at some iomem or ioport address, but aren't on any specific bus), they
> should be registered as platform devices; if these are system devices
> (core devices for basic operation; can live with IRQs off for suspend and 
> resume, or even require that) they should be registered as system devices.
Not sure. It's just a virtual bus. Some acpi devices haven't any
iomem/ioports. And some devices are platform devices and some not, which
means we must take care devices separately. We haven't a generic method
for all devices.

> 
> > 2. I regard all devices which don't belong to physical buses in the DSDT
> > as ACPI bus devices. Ideally, PCI devices, PNP devices & other devices
> > should bind them to their physical buses.
> 
> Yes, exactly.
> 
> > Since many devices listed in
> > DSDT aren't in ACPI bus, this makes it impossible to convert current
> > acpi driver model into Linux style.
> 
> Indeed. For each device, you need to decide which bus it resides on:
> > (CPU is in the bus)
> 
> No, CPUs are already registered as system devices. ( /sys/devices/system/cpu/ )
> Don't insert them twice into the device tree, please
Ok, might be a sysdevice driver.
> 
> >  So I'd like to remove the namespace hotplug interface later.
> Indeed, let's focus on this stuff later on.
> 
> So, let's look at the devices and where they should be registered. In most
> cases, it is just a guess on my side; system devices are suspended and
> resumed with interrupts off; that most probably should be a decisive point
> in this distinction.
> 
> +       "PNP0C09", /* EC */
> -> system or platform, not sure...
> 
> +       "ACPI0003", /* AC */
> -> platform
> 
> +       "PNP0C0F", /* Link */
> -> system. Might this already be registered on some systems? I have
> irqrouter, i8237 and i8259 in /sys/devices/system/
This one is broken for a long time. It can't be suspend/resume with
interrupt disabled.
> 
> +       "PNP0C0A", /* battery */
> -> platform
> 
> +       "PNP0C0C", "PNP0C0E", "PNP0C0D", "ACPI_FPB" ,"ACPI_FSB", /* button */
> -> platform
> 
> +       "PNP0C0B", /* fan */
> -> platform
> 
> +       "PNP0A03", /* PCI root */
> -> system or platform, not sure either.... Please make sure that "pci0000:00" or
>    whatever is registered as a child of this device.
> 
> +       ACPI_POWER_HID, /* power */
> -> platform
> 
> +       ACPI_PROCESSOR_HID, /* CPU */
> -> system, is already there...
> 
> +       ACPI_THERMAL_HID, /* thermal */
> -> platform
> 
> 
> Also, you might think about adding all these devices to "class ACPI".
> /sys/class/acpi/ is perfectly valid; there you can add some common
> infrastrucutre for _all_ ACPI-enumerated devices, rely on "class interface"
> and other methods available.


Thanks,
Shaohua



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Re: [RFC 0/2]convert ACPI driver model to Linux driver model

[Adam Belay]

Hi Shaohua,

I'm sorry for the late reply.

On Mon, Sep 12, 2005 at 01:22:22PM +0800, Shaohua Li wrote:
> Hi,
> I'm sending the patches out not for merging but for comments. The
> patches try to convert ACPI driver model to Linux driver model. There
> are still many things unsettled. If you have any
> comment/suggestion/requirement, please let me know.
> 
> 1. in my mind, acpi should export two sets of info in sysfs. One is
> current namespace subsystem, it should just export the firmware info.
> All acpi device/drivers related info don't export here. The other is
> ACPI bus. It's similar with other buses like PCI bus.

I'm not sure if we want to export the ACPI namespace in sysfs.  In
theory, we can attach most of that information on to the device tree
directly.  I agree that an ACPI bus would be useful.  I think it should
represent every device that can't be enumerated by another standard.

> 
> 2. I regard all devices which don't belong to physical buses in the DSDT
> as ACPI bus devices. Ideally, PCI devices, PNP devices & other devices
> should bind them to their physical buses. Since many devices listed in
> DSDT aren't in ACPI bus, this makes it impossible to convert current
> acpi driver model into Linux style. You might look at my patch, many
> routines required by Linux driver model are empty. Though we can't
> completely utilize the advantage of Linux driver model, the partial
> convert still benefits us many such as sysfs support and suspend/resume
> support.

This partial implementation has its advantages, but it's also important
to have a well defined plan of transition.  I think we should migrate the
ACPI code entirely to the linux driver model.  I've made some progress on
this issue.

> 
> 3. The acpi namespace hotplug interface looks strange. After we
> introduce ACPI bus (CPU is in the bus), we can send hotplug event
> through it. So I'd like to remove the namespace hotplug interface later.

Agreed.

> 
> There are something to prevent us from completely converting ACPI driver
> model to Linux style:
> 1. Current ACPI driver model can register drivers for all devices listed
> in DSDT. ACPI bus can't handle this.

I'm assuming you're referring to devices that don't need ACPI for
enumeration.  All other types shouldn't be a problem.

I've ran into this with some of my PCI bus code.  My current strategy is
to move the responsibility of attaching firmware data to the specific
device driver of the device in question rather than having the ACPI bus
handle it.  The idea is that only ACPI-aware drivers will utilize ACPI,
otherwise it will be ignored.  Essentially, ACPI aware devices will serve
as anchoring points for ACPI objects, including those that belong to the
ACPI Bus type.  Any comments?

> 2. Current ACPI hotplug (CPU/IO) relays on separate .add/.start
> callbacks, but Linux driver can only provide a .probe. We might split
> ACPI hotplug support to separate drivers.
> Since these, my patch just adds fake Linux driver model support, but it
> still is very useful.

This was also an issue that I came across.

Could you explain the role of .add/.start and why it's necessary?  It
may be reasonable to add this functionality to the Linux driver model
so that other drivers can utilize it.


I would appreciate any comments.

Thanks,
Adam


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Re: [RFC 0/2]convert ACPI driver model to Linux driver model

[Adam Belay]

On Mon, Sep 12, 2005 at 07:57:41PM +0200, Dominik Brodowski wrote:
> Hi,
> 
> On Mon, Sep 12, 2005 at 01:22:22PM +0800, Shaohua Li wrote:
> > I'm sending the patches out not for merging but for comments. The
> > patches try to convert ACPI driver model to Linux driver model. 
> 
> Excellent.
> 
> > 1. in my mind, acpi should export two sets of info in sysfs. One is
> > current namespace subsystem, it should just export the firmware info.
> > All acpi device/drivers related info don't export here. The other is
> > ACPI bus. It's similar with other buses like PCI bus.
> 
> However, there is no physical ACPI bus. Therefore, it shouldn't exist in
> /sys/devices/ or /sys/bus/. If they are platform devices (devices which can be
> poked at some iomem or ioport address, but aren't on any specific bus), they
> should be registered as platform devices; if these are system devices
> (core devices for basic operation; can live with IRQs off for suspend and 
> resume, or even require that) they should be registered as system devices.

In theory this makes sense, but in practice I think it's very difficult.  The
ACPI specification clearly intends for these representions to show up as real
physical devices.  One of the goals of ACPI is to look like a physical bus for
platform hardware.  Hence, ACPI provides detection, identification, power
management, and other bus-like services.

Also, in the driver model, we don't have physical bus types.  Rather buses are
just collections of devices that have the same interface for detection,
identification, power management, etc.  In general, a bus is just an API for
talking to a type of physical hardware.  Some have even used "struct bus_type"
to represent subcomponents of a physical device (see the PCI Express Port
Driver). Therefore, I think it's very natural to create an ACPI "struct
bus_type".  Every device that utilizes ACPI for detection, power management,
etc... would belong to this bus_type.  I see "struct bus_type" as a type of
physical device class.

Also, platform devices are rather ugly, and I would argue that it may make sense
to eventually remove them from the driver model.  They don't show device tree
dependencies properly and in many ways are just a hack, so it may be better to
register platform devices without a bus or with a legacy bus like ISA depending
on the situation.

> 
> > 2. I regard all devices which don't belong to physical buses in the DSDT
> > as ACPI bus devices. Ideally, PCI devices, PNP devices & other devices
> > should bind them to their physical buses.
> 
> Yes, exactly.
> 
> > Since many devices listed in
> > DSDT aren't in ACPI bus, this makes it impossible to convert current
> > acpi driver model into Linux style.
> 
> Indeed. For each device, you need to decide which bus it resides on:
> > (CPU is in the bus)
> 
> No, CPUs are already registered as system devices. ( /sys/devices/system/cpu/ )
> Don't insert them twice into the device tree, please

Once again, I'm not sure if I agree here.  When ACPI is the root bus, we can
represent things like ACPI wants.  When we're using PnPBIOS or a legacy root
bus, we can use system devices or whatever.  Still, this issue is rather
complex and needs to be worked out.

> 
> >  So I'd like to remove the namespace hotplug interface later.
> Indeed, let's focus on this stuff later on.
> 
> So, let's look at the devices and where they should be registered. In most
> cases, it is just a guess on my side; system devices are suspended and
> resumed with interrupts off; that most probably should be a decisive point
> in this distinction.
> 
> +       "PNP0C09", /* EC */
> -> system or platform, not sure...
> 
> +       "ACPI0003", /* AC */
> -> platform
> 
> +       "PNP0C0F", /* Link */
> -> system. Might this already be registered on some systems? I have
> irqrouter, i8237 and i8259 in /sys/devices/system/
> 
> +       "PNP0C0A", /* battery */
> -> platform
> 
> +       "PNP0C0C", "PNP0C0E", "PNP0C0D", "ACPI_FPB" ,"ACPI_FSB", /* button */
> -> platform
> 
> +       "PNP0C0B", /* fan */
> -> platform
> 
> +       "PNP0A03", /* PCI root */
> -> system or platform, not sure either.... Please make sure that "pci0000:00" or
>    whatever is registered as a child of this device.
> 
> +       ACPI_POWER_HID, /* power */
> -> platform
> 
> +       ACPI_PROCESSOR_HID, /* CPU */
> -> system, is already there...
> 
> +       ACPI_THERMAL_HID, /* thermal */
> -> platform

I'd argue all of these should appear in the device tree.  Their drivers want
to use the ACPI bus interface and will bind in a fashion identical to real
physical devices.

> 
> 
> Also, you might think about adding all these devices to "class ACPI".
> /sys/class/acpi/ is perfectly valid; there you can add some common
> infrastructure for _all_ ACPI-enumerated devices, rely on "class interface"
> and other methods available.

I have some thoughts on this issue also, but it's probably best that we
focus on physical ACPI device representation for now.

Thanks,
Adam



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Re: [RFC 0/2]convert ACPI driver model to Linux driver model

[Shaohua Li]

Hi,
On Wed, 2005-09-21 at 00:31 -0400, Adam Belay wrote:
> 
> On Mon, Sep 12, 2005 at 01:22:22PM +0800, Shaohua Li wrote:
> > Hi,
> > I'm sending the patches out not for merging but for comments. The
> > patches try to convert ACPI driver model to Linux driver model. There
> > are still many things unsettled. If you have any
> > comment/suggestion/requirement, please let me know.
> > 
> > 1. in my mind, acpi should export two sets of info in sysfs. One is
> > current namespace subsystem, it should just export the firmware info.
> > All acpi device/drivers related info don't export here. The other is
> > ACPI bus. It's similar with other buses like PCI bus.
> 
Thanks for your time to look at it.

> I'm not sure if we want to export the ACPI namespace in sysfs.  In
> theory, we can attach most of that information on to the device tree
> directly.  I agree that an ACPI bus would be useful.  I think it should
> represent every device that can't be enumerated by another standard.
I guess we can delay the discussion about if ACPI namespace should be in
sysfs. We can do it after converting ACPI to Linux driver model.

> > 
> > 2. I regard all devices which don't belong to physical buses in the DSDT
> > as ACPI bus devices. Ideally, PCI devices, PNP devices & other devices
> > should bind them to their physical buses. Since many devices listed in
> > DSDT aren't in ACPI bus, this makes it impossible to convert current
> > acpi driver model into Linux style. You might look at my patch, many
> > routines required by Linux driver model are empty. Though we can't
> > completely utilize the advantage of Linux driver model, the partial
> > convert still benefits us many such as sysfs support and suspend/resume
> > support.
> 
> This partial implementation has its advantages, but it's also important
> to have a well defined plan of transition.  I think we should migrate the
> ACPI code entirely to the linux driver model.  I've made some progress on
> this issue.
I have some troubles to migrate ACPI code entirely to linux driver model
(I mentioned in my previous email). It would be great to look at your
patches if possible.

> > 
> > 3. The acpi namespace hotplug interface looks strange. After we
> > introduce ACPI bus (CPU is in the bus), we can send hotplug event
> > through it. So I'd like to remove the namespace hotplug interface later.
> 
> Agreed.
> 
> > 
> > There are something to prevent us from completely converting ACPI driver
> > model to Linux style:
> > 1. Current ACPI driver model can register drivers for all devices listed
> > in DSDT. ACPI bus can't handle this.
> 
> I'm assuming you're referring to devices that don't need ACPI for
> enumeration.  All other types shouldn't be a problem.
Yes, exactly.

> 
> I've ran into this with some of my PCI bus code.  My current strategy is
> to move the responsibility of attaching firmware data to the specific
> device driver of the device in question rather than having the ACPI bus
> handle it.  The idea is that only ACPI-aware drivers will utilize ACPI,
> otherwise it will be ignored.  Essentially, ACPI aware devices will serve
> as anchoring points for ACPI objects, including those that belong to the
> ACPI Bus type.  Any comments?
So only devices belonging to ACPI bus can register ACPI driver and other
devices listed in ACPI table can have an ACPI handler and execute some
ACPI methods but they can't register an ACPI driver, right? Looks good.
I also have similar idea. In my mind, there are a firmware driver and an
ACPI driver. All devices listed in ACPI table are able to have a
firmware driver. Devices in ACPI bus can have an ACPI driver.

> 
> > 2. Current ACPI hotplug (CPU/IO) relays on separate .add/.start
> > callbacks, but Linux driver can only provide a .probe. We might split
> > ACPI hotplug support to separate drivers.
> > Since these, my patch just adds fake Linux driver model support, but it
> > still is very useful.
> 
> This was also an issue that I came across.
> 
> Could you explain the role of .add/.start and why it's necessary?  It
> may be reasonable to add this functionality to the Linux driver model
> so that other drivers can utilize it.
Let's see an example of ACPI PCI root bridge hotplug. When a new root
bridge is added, the root bridge's .added (scan PCI devices) method is
called. And after we we allocated resources to PCI devices under the
bridge, we start (call .start, add PCI devices into global PCI tree, as
a result, binding devices with drivers) the bridge. The processor driver
is another example. The seperate .add/.start makes the driver can work
on both the non-hotplug and hotplug cases. The syntax mixed the
functionalities of controlling the device and controlling hotplug the
device. 

Thanks,
Shaohua



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