[PATCH] block: mtip32xx: remove HOTPLUG_PCI_PCIE dependancy

[PATCH] block: mtip32xx: remove HOTPLUG_PCI_PCIE dependancy

[Greg KH]

This removes the HOTPLUG_PCI_PCIE dependency on the driver and makes it
depend on PCI.

Cc: Sam Bradshaw <sbradshaw@micron.com>
Cc: Asai Thambi S P <asamymuthupa@micron.com>
Cc: Jens Axboe <jaxboe@fusionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
Note, the driver builds just fine without this dependency, and I have a
system that does not have HOTPLUG PCIE, yet it has PCIE slots, which
should be all that is required for this driver.

What am I missing that required this dependency in the first place?

diff --git a/drivers/block/mtip32xx/Kconfig b/drivers/block/mtip32xx/Kconfig
index b5dd14e..0ba837f 100644
--- a/drivers/block/mtip32xx/Kconfig
+++ b/drivers/block/mtip32xx/Kconfig
@@ -4,6 +4,6 @@
 
 config BLK_DEV_PCIESSD_MTIP32XX
 	tristate "Block Device Driver for Micron PCIe SSDs"
-	depends on HOTPLUG_PCI_PCIE
+	depends on PCI
 	help
           This enables the block driver for Micron PCIe SSDs.

Re: [PATCH] block: mtip32xx: remove HOTPLUG_PCI_PCIE dependancy

[Jens Axboe]

On 2012-04-11 20:34, Greg KH wrote:
> This removes the HOTPLUG_PCI_PCIE dependency on the driver and makes it
> depend on PCI.

I think it's an old dependency. I've built and run it here without as
well, and no functional issues either.

Sam/Asai?

-- 
Jens Axboe

Re: [PATCH] block: mtip32xx: remove HOTPLUG_PCI_PCIE dependancy

[Asai Thambi S P]

On 4/11/2012 12:57 PM, Jens Axboe wrote:

> On 2012-04-11 20:34, Greg KH wrote:
>> This removes the HOTPLUG_PCI_PCIE dependency on the driver and makes it
>> depend on PCI.
> 
> I think it's an old dependency. I've built and run it here without as
> well, and no functional issues either.
> 
> Sam/Asai?
> 


Both driver and device will work fine without PCIe hotplug dependency. This
dependency is required for supporting surprise removal and surprise insertion
of the device on systems with PCIe hotplug controller.

--
Regards,
Asai Thambi

Re: [PATCH] block: mtip32xx: remove HOTPLUG_PCI_PCIE dependancy

[Jens Axboe]

On 2012-04-11 22:33, Asai Thambi S P wrote:
> On 4/11/2012 12:57 PM, Jens Axboe wrote:
> 
>> On 2012-04-11 20:34, Greg KH wrote:
>>> This removes the HOTPLUG_PCI_PCIE dependency on the driver and makes it
>>> depend on PCI.
>>
>> I think it's an old dependency. I've built and run it here without as
>> well, and no functional issues either.
>>
>> Sam/Asai?
>>
> 
> 
> Both driver and device will work fine without PCIe hotplug dependency. This
> dependency is required for supporting surprise removal and surprise insertion
> of the device on systems with PCIe hotplug controller.

That goes for all devices, though. So I think we can safely remove this
dependency. Nobody should expect hotplug/removal to work, without
actually including that :-)

If you or Sam would formally ack the patch, then I'll add it to the
pending mtip32xx series.

-- 
Jens Axboe

Re: [PATCH] block: mtip32xx: remove HOTPLUG_PCI_PCIE dependancy

[Asai Thambi S P]

On 4/11/2012 1:38 PM, Jens Axboe wrote:

> On 2012-04-11 22:33, Asai Thambi S P wrote:
>> On 4/11/2012 12:57 PM, Jens Axboe wrote:
>>
>>> On 2012-04-11 20:34, Greg KH wrote:
>>>> This removes the HOTPLUG_PCI_PCIE dependency on the driver and makes it
>>>> depend on PCI.
>>>
>>> I think it's an old dependency. I've built and run it here without as
>>> well, and no functional issues either.
>>>
>>> Sam/Asai?
>>>
>>
>>
>> Both driver and device will work fine without PCIe hotplug dependency. This
>> dependency is required for supporting surprise removal and surprise insertion
>> of the device on systems with PCIe hotplug controller.
> 
> That goes for all devices, though. So I think we can safely remove this
> dependency. Nobody should expect hotplug/removal to work, without
> actually including that :-)
> 
> If you or Sam would formally ack the patch, then I'll add it to the
> pending mtip32xx series.
> 

Acked-by: Asai Thambi S P <asamymuthupa@micron.com>

--
Regards,
Asai Thambi

Re: [PATCH] block: mtip32xx: remove HOTPLUG_PCI_PCIE dependancy

[Jens Axboe]

On 04/12/2012 02:46 AM, Asai Thambi S P wrote:
> On 4/11/2012 1:38 PM, Jens Axboe wrote:
> 
>> On 2012-04-11 22:33, Asai Thambi S P wrote:
>>> On 4/11/2012 12:57 PM, Jens Axboe wrote:
>>>
>>>> On 2012-04-11 20:34, Greg KH wrote:
>>>>> This removes the HOTPLUG_PCI_PCIE dependency on the driver and makes it
>>>>> depend on PCI.
>>>>
>>>> I think it's an old dependency. I've built and run it here without as
>>>> well, and no functional issues either.
>>>>
>>>> Sam/Asai?
>>>>
>>>
>>>
>>> Both driver and device will work fine without PCIe hotplug dependency. This
>>> dependency is required for supporting surprise removal and surprise insertion
>>> of the device on systems with PCIe hotplug controller.
>>
>> That goes for all devices, though. So I think we can safely remove this
>> dependency. Nobody should expect hotplug/removal to work, without
>> actually including that :-)
>>
>> If you or Sam would formally ack the patch, then I'll add it to the
>> pending mtip32xx series.
>>
> 
> Acked-by: Asai Thambi S P <asamymuthupa@micron.com>

Thanks applied Gregs patch - I see the two of you battled it out while I
was sound asleep ;-)

-- 
Jens Axboe

Re: [PATCH] block: mtip32xx: remove HOTPLUG_PCI_PCIE dependancy

[Greg KH]

On Wed, Apr 11, 2012 at 01:33:39PM -0700, Asai Thambi S P wrote:
> On 4/11/2012 12:57 PM, Jens Axboe wrote:
> 
> > On 2012-04-11 20:34, Greg KH wrote:
> >> This removes the HOTPLUG_PCI_PCIE dependency on the driver and makes it
> >> depend on PCI.
> > 
> > I think it's an old dependency. I've built and run it here without as
> > well, and no functional issues either.
> > 
> > Sam/Asai?
> > 
> 
> 
> Both driver and device will work fine without PCIe hotplug dependency. This
> dependency is required for supporting surprise removal and surprise insertion
> of the device on systems with PCIe hotplug controller.

But that's not a driver-specific thing at all.  All PCI drivers need to
be able to handle this (I like how you constantly check the pci id,
that's cute.)

So I think a basic dependancy on PCI should be fine here.

thanks,

greg k-h

Re: [PATCH] block: mtip32xx: remove HOTPLUG_PCI_PCIE dependancy

[Asai Thambi S P]

On 4/11/2012 1:40 PM, Greg KH wrote:

> On Wed, Apr 11, 2012 at 01:33:39PM -0700, Asai Thambi S P wrote:
>> On 4/11/2012 12:57 PM, Jens Axboe wrote:
>>
>>> On 2012-04-11 20:34, Greg KH wrote:
>>>> This removes the HOTPLUG_PCI_PCIE dependency on the driver and makes it
>>>> depend on PCI.
>>>
>>> I think it's an old dependency. I've built and run it here without as
>>> well, and no functional issues either.
>>>
>>> Sam/Asai?
>>>
>>
>>
>> Both driver and device will work fine without PCIe hotplug dependency. This
>> dependency is required for supporting surprise removal and surprise insertion
>> of the device on systems with PCIe hotplug controller.
> 
> But that's not a driver-specific thing at all.  All PCI drivers need to
> be able to handle this (I like how you constantly check the pci id,
> that's cute.)
> 
> So I think a basic dependancy on PCI should be fine here.

The P320 is different from existing PCIe devices supporting surprise removal
and surprise insertion (SRSI) capability (aka hotplug). We equate the hotplug
functionality enabled by PCIe hotplug controllers to that of any other storage
endpoint (SAS, SATA, FC, etc). For those devices, hotplug functionality is
enabled by the transport layer and propagated up to host storage stack for
handling.

There are two types of users for P320 device – 1) those with systems that have
PCIe hotplug controllers and intend to use hotplug and 2) those who do not
need or intend to use hotplug. The HOTPLUG_PCI_PCIE dependency enables users
in the first bucket to use the device’s capability without affecting those in
the second bucket.  While there aren’t many systems today that have PCIe
hotplug controllers, you will begin to see such systems very soon.

The mtip32xx driver depends on remove() being called for graceful handling of
surprise removal events.  Such cleanup is necessary to enable clean surprise
insertion of the same/different device in the same slot. We do check the PCI
id in non-fast path code to detect the surprise removal and fail any
outstanding I/Os with -ENODEV, but the driver still depends on the pci core
with help from the pcie hotplug module to call remove() for cleanup, hence the
HOTPLUG_PCI_PCIE dependency.

--
Regards,
Asai Thambi

Re: [PATCH] block: mtip32xx: remove HOTPLUG_PCI_PCIE dependancy

[Greg KH]

On Wed, Apr 11, 2012 at 03:22:56PM -0700, Asai Thambi S P wrote:
> On 4/11/2012 1:40 PM, Greg KH wrote:
> 
> > On Wed, Apr 11, 2012 at 01:33:39PM -0700, Asai Thambi S P wrote:
> >> On 4/11/2012 12:57 PM, Jens Axboe wrote:
> >>
> >>> On 2012-04-11 20:34, Greg KH wrote:
> >>>> This removes the HOTPLUG_PCI_PCIE dependency on the driver and makes it
> >>>> depend on PCI.
> >>>
> >>> I think it's an old dependency. I've built and run it here without as
> >>> well, and no functional issues either.
> >>>
> >>> Sam/Asai?
> >>>
> >>
> >>
> >> Both driver and device will work fine without PCIe hotplug dependency. This
> >> dependency is required for supporting surprise removal and surprise insertion
> >> of the device on systems with PCIe hotplug controller.
> > 
> > But that's not a driver-specific thing at all.  All PCI drivers need to
> > be able to handle this (I like how you constantly check the pci id,
> > that's cute.)
> > 
> > So I think a basic dependancy on PCI should be fine here.
> 
> The P320 is different from existing PCIe devices supporting surprise removal
> and surprise insertion (SRSI) capability (aka hotplug). We equate the hotplug
> functionality enabled by PCIe hotplug controllers to that of any other storage
> endpoint (SAS, SATA, FC, etc). For those devices, hotplug functionality is
> enabled by the transport layer and propagated up to host storage stack for
> handling.

Huh?  No, hotplug on Linux happens on the PCI level, and has done so for
over 10 years.

> There are two types of users for P320 device – 1) those with systems that have
> PCIe hotplug controllers and intend to use hotplug and 2) those who do not
> need or intend to use hotplug. The HOTPLUG_PCI_PCIE dependency enables users
> in the first bucket to use the device’s capability without affecting those in
> the second bucket.

No, it prevents the users in the second group from ever using this
driver as it will not be built at all.

I have such a system right here, and I want to use the device, yet could
not as I do not have HOTPLUG_PCI_PCIE enabled in my kernel because I do
not have that type of PCI Hotplug controller.

> While there aren’t many systems today that have PCIe
> hotplug controllers, you will begin to see such systems very soon.

Manufacturers have been telling me that for over 10 years ago, when I
got the first PCI Hotplug driver merged into the kernel tree :)

> The mtip32xx driver depends on remove() being called for graceful handling of
> surprise removal events.

As it should, nothing new there, that's how PCI hotplug works.

> Such cleanup is necessary to enable clean surprise
> insertion of the same/different device in the same slot. We do check the PCI
> id in non-fast path code to detect the surprise removal and fail any
> outstanding I/Os with -ENODEV, but the driver still depends on the pci core
> with help from the pcie hotplug module to call remove() for cleanup, hence the
> HOTPLUG_PCI_PCIE dependency.

No, that's not a valid dependency at all, sorry.

All you should depend on is CONFIG_PCI and CONFIG_BLOCK.  Your driver
doesn't know, or care, if the system is a PCI hotplug one, as that is
how we architected the PCI hotplug layer.  Otherwise all PCI drivers
would have to have this type of logic in it, and that would be a lot of
extra work for no good reason.

So, I still think this dependency should be removed, the fact that I'm
typing this from a system running on this card at the moment, without
PCIE hotplug capabilities, kind of proves it :)

thanks,

greg k-h

Re: [PATCH] block: mtip32xx: remove HOTPLUG_PCI_PCIE dependancy

[Asai Thambi S P]

On 4/11/2012 3:37 PM, Greg KH wrote:

> On Wed, Apr 11, 2012 at 03:22:56PM -0700, Asai Thambi S P wrote:
>> On 4/11/2012 1:40 PM, Greg KH wrote:
>>
>>> On Wed, Apr 11, 2012 at 01:33:39PM -0700, Asai Thambi S P wrote:
>>>> On 4/11/2012 12:57 PM, Jens Axboe wrote:
>>>>
>>>>> On 2012-04-11 20:34, Greg KH wrote:
>>>>>> This removes the HOTPLUG_PCI_PCIE dependency on the driver and makes it
>>>>>> depend on PCI.
>>>>>
>>>>> I think it's an old dependency. I've built and run it here without as
>>>>> well, and no functional issues either.
>>>>>
>>>>> Sam/Asai?
>>>>>
>>>>
>>>>
>>>> Both driver and device will work fine without PCIe hotplug dependency. This
>>>> dependency is required for supporting surprise removal and surprise insertion
>>>> of the device on systems with PCIe hotplug controller.
>>>
>>> But that's not a driver-specific thing at all.  All PCI drivers need to
>>> be able to handle this (I like how you constantly check the pci id,
>>> that's cute.)
>>>
>>> So I think a basic dependancy on PCI should be fine here.
>>
>> The P320 is different from existing PCIe devices supporting surprise removal
>> and surprise insertion (SRSI) capability (aka hotplug). We equate the hotplug
>> functionality enabled by PCIe hotplug controllers to that of any other storage
>> endpoint (SAS, SATA, FC, etc). For those devices, hotplug functionality is
>> enabled by the transport layer and propagated up to host storage stack for
>> handling.
> 
> Huh?  No, hotplug on Linux happens on the PCI level, and has done so for
> over 10 years.

Just to clarify, I was referring to hotplug of SAS/SATA/FC storage devices,
not HBA.

> 
>> There are two types of users for P320 device – 1) those with systems that have
>> PCIe hotplug controllers and intend to use hotplug and 2) those who do not
>> need or intend to use hotplug. The HOTPLUG_PCI_PCIE dependency enables users
>> in the first bucket to use the device’s capability without affecting those in
>> the second bucket.
> 
> No, it prevents the users in the second group from ever using this
> driver as it will not be built at all.
> 
> I have such a system right here, and I want to use the device, yet could
> not as I do not have HOTPLUG_PCI_PCIE enabled in my kernel because I do
> not have that type of PCI Hotplug controller.
> 
>> While there aren’t many systems today that have PCIe
>> hotplug controllers, you will begin to see such systems very soon.
> 
> Manufacturers have been telling me that for over 10 years ago, when I
> got the first PCI Hotplug driver merged into the kernel tree :)
> 
>> The mtip32xx driver depends on remove() being called for graceful handling of
>> surprise removal events.
> 
> As it should, nothing new there, that's how PCI hotplug works.
> 
>> Such cleanup is necessary to enable clean surprise
>> insertion of the same/different device in the same slot. We do check the PCI
>> id in non-fast path code to detect the surprise removal and fail any
>> outstanding I/Os with -ENODEV, but the driver still depends on the pci core
>> with help from the pcie hotplug module to call remove() for cleanup, hence the
>> HOTPLUG_PCI_PCIE dependency.
> 
> No, that's not a valid dependency at all, sorry.
> 
> All you should depend on is CONFIG_PCI and CONFIG_BLOCK.  Your driver
> doesn't know, or care, if the system is a PCI hotplug one, as that is
> how we architected the PCI hotplug layer.  Otherwise all PCI drivers
> would have to have this type of logic in it, and that would be a lot of
> extra work for no good reason.
> 
> So, I still think this dependency should be removed, the fact that I'm
> typing this from a system running on this card at the moment, without
> PCIE hotplug capabilities, kind of proves it :)

Agree to remove the dependency. I will reply to Jens email too.

--
Regards,
Asai Thambi

Re: [PATCH] block: mtip32xx: remove HOTPLUG_PCI_PCIE dependancy

[Greg KH]

On Wed, Apr 11, 2012 at 05:32:15PM -0700, Asai Thambi S P wrote:
> On 4/11/2012 3:37 PM, Greg KH wrote:
> 
> > On Wed, Apr 11, 2012 at 03:22:56PM -0700, Asai Thambi S P wrote:
> >> On 4/11/2012 1:40 PM, Greg KH wrote:
> >>
> >>> On Wed, Apr 11, 2012 at 01:33:39PM -0700, Asai Thambi S P wrote:
> >>>> On 4/11/2012 12:57 PM, Jens Axboe wrote:
> >>>>
> >>>>> On 2012-04-11 20:34, Greg KH wrote:
> >>>>>> This removes the HOTPLUG_PCI_PCIE dependency on the driver and makes it
> >>>>>> depend on PCI.
> >>>>>
> >>>>> I think it's an old dependency. I've built and run it here without as
> >>>>> well, and no functional issues either.
> >>>>>
> >>>>> Sam/Asai?
> >>>>>
> >>>>
> >>>>
> >>>> Both driver and device will work fine without PCIe hotplug dependency. This
> >>>> dependency is required for supporting surprise removal and surprise insertion
> >>>> of the device on systems with PCIe hotplug controller.
> >>>
> >>> But that's not a driver-specific thing at all.  All PCI drivers need to
> >>> be able to handle this (I like how you constantly check the pci id,
> >>> that's cute.)
> >>>
> >>> So I think a basic dependancy on PCI should be fine here.
> >>
> >> The P320 is different from existing PCIe devices supporting surprise removal
> >> and surprise insertion (SRSI) capability (aka hotplug). We equate the hotplug
> >> functionality enabled by PCIe hotplug controllers to that of any other storage
> >> endpoint (SAS, SATA, FC, etc). For those devices, hotplug functionality is
> >> enabled by the transport layer and propagated up to host storage stack for
> >> handling.
> > 
> > Huh?  No, hotplug on Linux happens on the PCI level, and has done so for
> > over 10 years.
> 
> Just to clarify, I was referring to hotplug of SAS/SATA/FC storage devices,
> not HBA.

Ah, ok, yes, you are right, but as you aren't using the SCSI layer here
(odd, but ok), you can only handle hotplug at the PCI layer.

thanks,

greg k-h