On 10/21/2016 2:35 AM, Alex Williamson wrote:
> On Fri, 21 Oct 2016 01:59:55 +0530
> Kirti Wankhede <kwankhede@xxxxxxxxxx> wrote:
>
>> On 10/21/2016 1:04 AM, Alex Williamson wrote:
>>> On Tue, 18 Oct 2016 02:52:10 +0530
>>> Kirti Wankhede <kwankhede@xxxxxxxxxx> wrote:
>>>
>>>> Function vfio_device_api_string() returns string based on flag set in
>>>> vfio_device_info's flag. This should be used by vendor driver to get string
>>>> based on flag for device_api attribute.
>>>>
>>>> Signed-off-by: Kirti Wankhede <kwankhede@xxxxxxxxxx>
>>>> Signed-off-by: Neo Jia <cjia@xxxxxxxxxx>
>>>> Change-Id: I42d29f475f02a7132ce13297fbf2b48f1da10995
>>>> ---
>>>> drivers/vfio/vfio.c | 15 +++++++++++++++
>>>> include/linux/vfio.h | 2 ++
>>>> 2 files changed, 17 insertions(+)
>>>>
>>>> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
>>>> index 10ef1c5fa762..aec470454a13 100644
>>>> --- a/drivers/vfio/vfio.c
>>>> +++ b/drivers/vfio/vfio.c
>>>> @@ -1917,6 +1917,21 @@ int vfio_set_irqs_validate_and_prepare(struct vfio_irq_set *hdr, int num_irqs,
>>>> }
>>>> EXPORT_SYMBOL(vfio_set_irqs_validate_and_prepare);
>>>>
>>>> +const char *vfio_device_api_string(u32 flags)
>>>> +{
>>>> + if (flags & VFIO_DEVICE_FLAGS_PCI)
>>>> + return "vfio-pci";
>>>> +
>>>> + if (flags & VFIO_DEVICE_FLAGS_PLATFORM)
>>>> + return "vfio-platform";
>>>> +
>>>> + if (flags & VFIO_DEVICE_FLAGS_AMBA)
>>>> + return "vfio-amba";
>>>> +
>>>> + return "";
>>>> +}
>>>> +EXPORT_SYMBOL(vfio_device_api_string);
>>>> +
>>>> /*
>>>> * Pin a set of guest PFNs and return their associated host PFNs for local
>>>> * domain only.
>>>> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
>>>> index 31d059f1649b..fca2bf23c4f1 100644
>>>> --- a/include/linux/vfio.h
>>>> +++ b/include/linux/vfio.h
>>>> @@ -116,6 +116,8 @@ extern int vfio_set_irqs_validate_and_prepare(struct vfio_irq_set *hdr,
>>>> int num_irqs, int max_irq_type,
>>>> size_t *data_size);
>>>>
>>>> +extern const char *vfio_device_api_string(u32 flags);
>>>> +
>>>> struct pci_dev;
>>>> #ifdef CONFIG_EEH
>>>> extern void vfio_spapr_pci_eeh_open(struct pci_dev *pdev);
>>>
>>> Couldn't this simply be a #define in the uapi header?
>>>
>>> #define VFIO_DEVICE_PCI_API_STRING "vfio-pci"
>>>
>>> I don't really see why we need a lookup function.
>>>
>>
>> String is tightly coupled with the FLAG, right?
>> Instead user need to take care of making sure to return proper string,
>> and don't mis-match the string, I think having function is easier.
>
> That's exactly why I proposed putting the #define string in the uapi,
> by that I mean the vfio uapi header. That keeps the tight coupling to
> the flag, they're both defined in the same place, plus it gives
> userspace a reference so they're not just inventing a string to compare
> against. IOW, the vendor driver simply does an sprintf of
> VFIO_DEVICE_PCI_API_STRING and userspace (ie. libvirt) can do a strcmp
> with VFIO_DEVICE_PCI_API_STRING from the same header and everybody
> arrives at the same result.
>
>> Vendor driver should decide the type of device they want to expose and
>> set the flag, using this function vendor driver would return string
>> which is based on flag they set.
>
> Being a function adds no intrinsic value and being in a uapi header does
> add value to userspace. Thanks,
>
Ok. The strings should be in uapi, but having function (like below) to
return proper string based on flag would be good to have for vendor driver.
+const char *vfio_device_api_string(u32 flags)
+{
+ if (flags & VFIO_DEVICE_FLAGS_PCI)
+ return VFIO_DEVICE_API_PCI_STRING;
+
+ if (flags & VFIO_DEVICE_FLAGS_PLATFORM)
+ return VFIO_DEVICE_API_PLATFORM_STRING;
+
+ if (flags & VFIO_DEVICE_FLAGS_AMBA)
+ return VFIO_DEVICE_API_AMBA_STRING;
+
+ return "";
+}
+EXPORT_SYMBOL(vfio_device_api_string);
Kirti
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