On Tue, Jul 12, 2016 at 11:13:00AM +0200, Christoph Hellwig wrote:

On Mon, Jul 11, 2016 at 12:43:41PM +0200, Alexander Gordeev wrote:

quoted

quoted

I diagreed - if we deprecated functions the only thing that should
be mentioned is a "don't use these". 

I will try to paraphrase myself. The new API deprecates pci_enable_msi*_range
functions, but I am not that sure about others. Certainly, pci_msi*_vec__ount
and pci_enable_msi*_exact could have (and AFAIR do have) uses that can not be
covered by automatic initialization of pci_alloc_irq_vectors().

pci_enable_msi*_exact is the equivalent of pci_enable_msi*_range
with minvecs == maxvecs and treating any return value >= 0 as 0.

Right. And people asked explicitly to introduce these helpers when
range functions were introduced in the first place. Since there is
handful of drivers that do use pci_enable_msi*_exact() I suppose a
need for them persists.

I've updated the documentation so that the old usage examples are kept
around, but now use pci_alloc_irq_vectors.  I've also added a more detaild
blurb on pci_msi*_vec_count - I think there is no need for them, but
if I'm proven wrong we'll have to add a pci_irq_vector_count that handles
all interrupt types later.

I guess, it is up to Bjorn. But.

Your proposed pci_nr_irq_vectors() function (a) is not a replacement for
pci_msi*_vec_count() and (b) would be useless if I read its description
properly:

(a) Functions pci_msi*_vec_count() return number of vectors reported by
a PCI device. It is a constant for the device and a driver may make an
assumption based on this number;

(b) A number returned by pci_nr_irq_vectors() is not guaranteed what a
following call to pci_alloc_irq_vectors() can return (since the number
of actually allocated vectors might change between the two calls).
Therefore, a value returned by pci_nr_irq_vectors() can not be used for
anything.