On 06 Nov 2015, at 08:51, Vadim Rozenfeld <vrozenfe@redhat.com> wrote:

On Thu, 2015-11-05 at 21:46 +0000, Richard W.M. Jones wrote:

On Thu, Oct 29, 2015 at 11:05:42AM +1100, Vadim Rozenfeld wrote:

On Wed, 2015-10-28 at 14:53 +0300, Roman Kagan wrote:

 1) tell which devices can be configured

Not sure that I fully understated your question. but if you are going to
create some sort of off-line automatic virtio-win drivers update
utility, then it shouldn't be too complicated. Firs of all you will need
to obtain the Windows kernel version by reading the following Registry
key - "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion". Let's say it
6.3, which means that it is Win8.1 or WS2012R2, parsing "BuildLabEx"
string from the same hive will give you information about the platform
bitness. Next you need to go through inf files, and find "DriverVer"
string, like this one . taken from from vioscsi.inf

DriverVer=08/01/2015,62.72.104.10800

This string contains build time and version stamps. The version stamp
looks as follow "62.72.104.10800"
where 62 means a target Windows kernel version multiplied by 10. In this
case it is 6.2 which means Win8 or WS2012
72 - the target host platform version multiplied bu 10 (was RHEL7.2)
104 just a magic number, but it can be changed, don't make any
assumption based on this number.
10800 our internal build number (build 108) multiplied by 100

Hi Vadim,

I've almost finished implementing this, but I have a couple of
technical questions:

(1) How can we tell from the .inf file what architecture (x86 or
amd64) the driver is for?  There is a [Manufacturer] section which
looks hopeful, eg:

 [Manufacturer]
 %RHEL%   = RHEL,NTAMD64

but the contents are not very consistent across all the .inf files I
have access to.

Hi Richard,

It should be consistent. We do specify target architecture (amd64 or
x86) when stamping inf/inx files. IIRC, qemupciserial.inf is the only
exception, but it goes without binaries. In any case, if you are going
to use existing distribution media, you can rely on the media layout -
for example, if "amd64" is a part of your current path - you are in
64-bit directory. 

(2) If we have a directory containing multiple drivers, can we assume
that if any .inf file found matches the guest OS, then all those
drivers can be installed?  So far this appears to be true.  

Yes, we will never mix 32 and 64 bit drivers into the same directory.
I swear:) 

If not
then we have to start associating drivers with .inf files, which seems
a bit complicated.

(3) You write:

If you found an inf file with the matching minor OS (6 in our case)
version and matching or less but close minor version number (2 vs 3)
then you are in the right directory.

When you say "close minor version number" is there a particular
definition you have in mind?  eg. minor or minor-1 is OK?  Or do we
have to consider all .inf files in totality and choose the nearest
one?

Ideally, we should try finding the exact match. If not, we have to find
one with the same major version number and nearest minor number which is
smaller than the target one. For example, let's say we are looking for a
driver for Win8.1/WS2012R2, we know that both of them have kernel
version 6.3 . So, ideally we should to find inf file with the following
driver version string:

DriverVer=XX/YY/ZZZZ,63.AA.BBB.CCCCC

if we cannot find an inf file with such criteria, we should try finding
another one with the OS version 62 (which means that a driver was build
for kernel 6.2 Win8/WS2012 and technically should be compatible with
6.3). So, we are looking for DriverVer which looks like this one:
DriverVer=XX/YY/ZZZZ,62.AA.BBB.CCCCC

Still no luck - decrease the target OS version to 61 and repeat.

For WDF drivers like balloon, vioserial, and rng you can go as far as
you can trying to find an appropriate driver. 

For miniport drivers like netkvm ( Yan, please confirm ), viostor and
vioscsi I wouldn't go too far. For example drivers designed to fork in
specific stacks at kernel version 5.1 (WinXP) can refuse working with
kernel 6.2 (Win8).

However, Win10 will be a problem. At least as long as we do not release
virtio-win drivers built for this particular OS version, and keep using 
drivers designed for Win8/WS2012 and Win8.1/WS2012R2 platforms.
Win10 has kernel version 10.0 (guys, who has Win10 RTM running - please
confirm). It used to be 6.4 for RC and Beta versions, but IIRC
Microsoft decided to change it to 10.0 for RTM and final release. 
Microsoft promised that drivers designed for Win8/WS2012 and
Win8.1/WS2012R2 platforms will continue working, at least for the
nearest future.

Vadim.

Rich.