(2010/08/05 8:51), Rafael J. Wysocki wrote:
> On Wednesday, August 04, 2010, Rafael J. Wysocki wrote:
>> On Wednesday, August 04, 2010, Hidetoshi Seto wrote:
>>> (2010/08/04 14:46), Kenji Kaneshige wrote:
>>>> (2010/08/04 6:02), Rafael J. Wysocki wrote:
>>>>> On Tuesday, August 03, 2010, Rafael J. Wysocki wrote:
>>>>>> On Tuesday, August 03, 2010, Hidetoshi Seto wrote:
>>>>>>> (2010/08/03 13:52), Kenji Kaneshige wrote:
>>>>>>>> (2010/08/03 6:59), Rafael J. Wysocki wrote:
>>>>>>>>> @@ -434,19 +432,6 @@ acpi_status acpi_pci_osc_control_set(acp
>>>>>>>>> if ((root->osc_control_set& control_req) == control_req)
>>>>>>>>> goto out;
>>>>>>>>>
>>>>>>>>> - /* Need to query controls first before requesting them */
>>>>>>>>> - if (!root->osc_queried) {
>>>>>>>>> - status = acpi_pci_query_osc(root, root->osc_support_set, NULL);
>>>>>>>>> - if (ACPI_FAILURE(status))
>>>>>>>>> - goto out;
>>>>>>>>> - }
>>>>>>>>> - if ((root->osc_control_qry& control_req) != control_req) {
>>>>>>>>> - printk(KERN_DEBUG
>>>>>>>>> - "Firmware did not grant requested _OSC control\n");
>>>>>>>>> - status = AE_SUPPORT;
>>>>>>>>> - goto out;
>>>>>>>>> - }
>>>>>>>>
>>>>>>>> I think acpi_pci_osc_control_set() still need to query before commit
>>>>>>>> to ensure all the requested controls are granted to OS.
>>>>>>>>
>>>>>>>> So the code needs to be
>>>>>>>>
>>>>>>>> status = acpi_pci_query_osc(root, root->osc_support_set,&control_req);
>>>>>>>> if (ACPI_FAILURE(status))
>>>>>>>> goto out;
>>>>>>>
>>>>
>>>> Sorry, that should have been
>>>>
>>>> query = control_req;
>>>> status = acpi_pci_query_osc(root, root->osc_support_set, &query);
>>>> if (ACPI_FAILURE(status))
>>>> goto out;
>>>> if ((query & control_req) != control_req) {
>>>> printk_(KERN_DEBUG
>>>> "Firmware did not grant requested _OSC control\n");
>>>> status = AE_SUPPORT;
>>>> goto out;
>>>> }
>>>>
>>>> I know current pcie_port_acpi_setup() queries the requesting controls
>>>> before acpi_pci_osc_control_set() and only one control is requested
>>>> in the other code. However, I think acpi_pci_osc_control_set() still
>>>> need to query the requested controls to ensure all the requested
>>>> controls, in case someone calls this function without querying the
>>>> requesting controls. In other words, I think it must be ensured that
>>>> any controls are never granted to OS when acpi_pci_osc_control_set()
>>>> returns error.
>>>
>>> I think the following patch is what you mean.
>>>
>>> And... (Continue to next post)
>>>
>>> Thanks,
>>> H.Seto
>>
>> OK, I'll repalce my 7/8 with the patch below.
>
> Actually, having reconsidered that, I don't think this approach is valid.
>
> First, it has the problem that if acpi_pci_osc_control_set() returns error
> code, the caller doesn't really know whether the query failed, or the final
> request failed. Arguably, it won't matter for the majority of callers, but
> some of them might be interested in knowing that in principle.
Ugh... there are only 2 callers now and both of them are in the majority.
I don't think it is a time to take care of an invisible minority who might
require acpi_pci_osc_raw() to complete its work.
>
> Second, the callers that call acpi_pci_osc_control_query() before
> acpi_pci_osc_control_set() don't need the additional query inside
> of acpi_pci_osc_control_set().
So we can recommend all of callers not to call acpi_pci_osc_control_query()
before acpi_pci_osc_control_set().
I suppose that almost all of "the majority" just want to set fixed set of
controls and they will just return error when fails anyway.
>
> Therefore I'd prefer to have two separate functions, one for querying and the
> other for requesting control. Then, we can provide a helper that calls the
> both of them for the callers of acpi_pci_osc_control_set() that don't need
> to call acpi_pci_osc_control_query() directly by themselves.
I'm afraid the "two" is not enough for the minority.
Therefore I don't think it is a time to prepare for such an inexistent
minor usage.
>
> Given that acpi_pci_osc_control_query() is introduced by
> https://patchwork.kernel.org/patch/117176/ , the helper may be implemented
> like in the appended patch.
>
> After that patch, the $subject patch can be applied without any modifications
> to remove the no-longer-used fields in struct acpi_pci_root.
>
> Thanks,
> Rafael
>
> ---
> From: Rafael J. Wysocki <rjw@xxxxxxx>
> Subject: ACPI / PCI: Introduce function for requesting _OSC controls safely
>
> Calling raw acpi_pci_osc_control_set() is generally unsafe, because
> it may return error code even if control of some requested features
> have been granted by the BIOS. For this reason the callers of
> acpi_pci_osc_control_set() should call acpi_pci_osc_control_query()
> before it to make sure that the BIOS is willing to grant control of
> the requested features.
>
> Introduce helper function acpi_pci_osc_control_set_safe() allowing
> a caller of acpi_pci_osc_control_set() who is not interested in
> the control bits returned by acpi_pci_osc_control_query() to
> request control of _OSC features in a safe way.
>
> Make acpi_get_hp_hw_control_from_firmware() use the new function.
>
> Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
> ---
> drivers/acpi/pci_root.c | 24 ++++++++++++++++++++++++
> drivers/pci/hotplug/acpi_pcihp.c | 2 +-
> include/linux/acpi.h | 1 +
> 3 files changed, 26 insertions(+), 1 deletion(-)
>
> Index: linux-2.6/drivers/acpi/pci_root.c
> ===================================================================
> --- linux-2.6.orig/drivers/acpi/pci_root.c
> +++ linux-2.6/drivers/acpi/pci_root.c
> @@ -472,6 +472,30 @@ out:
> }
> EXPORT_SYMBOL(acpi_pci_osc_control_set);
>
> +/**
> + * acpi_pci_osc_control_set_safe - Query and set _OSC control bit mask.
> + * @handle: ACPI handle of a PCI root bridge (or PCIe Root Complex).
> + * @flags: Mask of _OSC bits to query and set.
> + *
> + * Check if the BIOS is willing to grant control of the features represented
> + * by @flags and request control of these features from it.
> + **/
> +acpi_status acpi_pci_osc_control_set_safe(acpi_handle handle, u32 flags)
> +{
> + acpi_status status;
> + u32 ctrl = flags;
> +
> + status = acpi_pci_osc_control_query(handle, &flags);
> + if (ACPI_FAILURE(status))
> + return status;
> + if ((ctrl & flags) != ctrl)
> + return AE_SUPPORT;
> +
> + status = acpi_pci_osc_control_set(handle, flags);
> + return status;
> +}
> +EXPORT_SYMBOL(acpi_pci_osc_control_set_safe);
> +
> static int __devinit acpi_pci_root_add(struct acpi_device *device)
> {
> unsigned long long segment, bus;
> Index: linux-2.6/drivers/pci/hotplug/acpi_pcihp.c
> ===================================================================
> --- linux-2.6.orig/drivers/pci/hotplug/acpi_pcihp.c
> +++ linux-2.6/drivers/pci/hotplug/acpi_pcihp.c
> @@ -358,7 +358,7 @@ int acpi_get_hp_hw_control_from_firmware
> acpi_get_name(handle, ACPI_FULL_PATHNAME, &string);
> dbg("Trying to get hotplug control for %s\n",
> (char *)string.pointer);
> - status = acpi_pci_osc_control_set(handle, flags);
> + status = acpi_pci_osc_control_set_safe(handle, flags);
> if (ACPI_SUCCESS(status))
> goto got_one;
> if (status == AE_SUPPORT)
> Index: linux-2.6/include/linux/acpi.h
> ===================================================================
> --- linux-2.6.orig/include/linux/acpi.h
> +++ linux-2.6/include/linux/acpi.h
> @@ -307,6 +307,7 @@ acpi_status acpi_run_osc(acpi_handle han
>
> extern acpi_status acpi_pci_osc_control_query(acpi_handle handle, u32 *mask);
> extern acpi_status acpi_pci_osc_control_set(acpi_handle handle, u32 flags);
> +extern acpi_status acpi_pci_osc_control_set_safe(acpi_handle handle, u32 flags);
> extern void acpi_early_init(void);
>
> #else /* !CONFIG_ACPI */
>
>
So I'd like to say NAK against this patch, sorry.
Thanks,
H.Seto
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