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From: Pavel A. on 3 Sep 2008 18:06
Ben Voigt [C++ MVP] wrote:
........
> It's USB/serial converter, from FTDI (doesn't use communication device
> class). Their driver is WHQL. I wouldn't doubt that their driver is
> causing the problem since one version ago simply opening a device on a
> multicore system was BSOD within 10 seconds. Which doesn't totally absolve
> MS of responsibility. What's the good of WHQL if even buggy drivers can be
> approved?

WHQL definitely does test on multicore machines.
Unlikely that a not SMP capable driver could pass.

> I should be able to load the problem configuration in a kernel
debugger and
> have debug output from my userland application showing the result of the
> device interface open.

Maybe adding debug prints around calls to the driver in the app can
help. You can call DebugPrintEx from usermode so messages will appear in
windbg or crash dump. Below is what I use.

Regards,
--PA

~~~~~~~~~~~~~ cut here ~~~~~~~~~~~~
#define _WIN32_WINNT 0x0501 // minimal platform: WinXP
#include <windows.h>

// Borrowed from DDK dpfilter.h
#define DPFLTR_ERROR_LEVEL 0
#define DPFLTR_WARNING_LEVEL 1
#define DPFLTR_TRACE_LEVEL 2
#define DPFLTR_INFO_LEVEL 3
#define DPFLTR_MASK 0x8000000

#define DPFLTR_IHVDRIVER_ID 77
#define DPFLTR_SYSTEM_ID 0
#define DPFLTR_VERIFIER_ID 93

extern ULONG ( __stdcall *f_vDbgPrintEx)( ULONG ComponentId, ULONG
Level, PCCH Format, va_list arglist);

void KernelDbgPrint( PCCH Fmt, ... )
{
ULONG n;
va_list arglist;

if( !vDbgPrintEx) ) {
FARPROC f;
HMODULE hm = _GLOBL_ GetModuleHandle(TEXT("ntdll.dll"));
f = _GLOBL_ GetProcAddress( hm, "vDbgPrintEx" );
if( !f ) return;
memcpy( &f_vDbgPrintEx, &f, sizeof(f) );
}

va_start( arglist, Fmt );
n = f_vDbgPrintEx( DPFLTR_IHVDRIVER_ID, DPFLTR_ERROR_LEVEL, Fmt, arglist );
va_end( arglist );
}

~~~~~~~~~~ cut here ~~~~~~~~
From: Ben Voigt [C++ MVP] on 5 Sep 2008 10:26
Pavel A. wrote:
> Ben Voigt [C++ MVP] wrote:
> .......
>> It's USB/serial converter, from FTDI (doesn't use communication
>> device class). Their driver is WHQL. I wouldn't doubt that their
>> driver is causing the problem since one version ago simply opening a
>> device on a multicore system was BSOD within 10 seconds. Which
>> doesn't totally absolve MS of responsibility. What's the good of
>> WHQL if even buggy drivers can be approved?
>
> WHQL definitely does test on multicore machines.
> Unlikely that a not SMP capable driver could pass.

Hmmm. Well, for some reason this driver did pass. Maybe some hardware
configurations avoid the buggy code (the same driver package supports
several different FTDI USB converter chips, and the virtual com port driver
can be loaded or not depending on settings in the EEPROM).

>
> > I should be able to load the problem configuration in a kernel
> debugger and
>> have debug output from my userland application showing the result of
>> the device interface open.
>
> Maybe adding debug prints around calls to the driver in the app can
> help. You can call DebugPrintEx from usermode so messages will appear
> in windbg or crash dump. Below is what I use.

I appreciate the code snippet, however it isn't much good to trace my
CreateFile call unless I can also enable tracing on the serenum and sermouse
drivers, so I can log a total ordering of the different port open and close
events (assuming that these are included in the driver trace output at all).

>
> Regards,
> --PA
>
> ~~~~~~~~~~~~~ cut here ~~~~~~~~~~~~
> #define _WIN32_WINNT 0x0501 // minimal platform: WinXP
> #include <windows.h>
>
> // Borrowed from DDK dpfilter.h
> #define DPFLTR_ERROR_LEVEL 0
> #define DPFLTR_WARNING_LEVEL 1
> #define DPFLTR_TRACE_LEVEL 2
> #define DPFLTR_INFO_LEVEL 3
> #define DPFLTR_MASK 0x8000000
>
> #define DPFLTR_IHVDRIVER_ID 77
> #define DPFLTR_SYSTEM_ID 0
> #define DPFLTR_VERIFIER_ID 93
>
> extern ULONG ( __stdcall *f_vDbgPrintEx)( ULONG ComponentId, ULONG
> Level, PCCH Format, va_list arglist);
>
> void KernelDbgPrint( PCCH Fmt, ... )
> {
> ULONG n;
> va_list arglist;
>
> if( !vDbgPrintEx) ) {
> FARPROC f;
> HMODULE hm = _GLOBL_ GetModuleHandle(TEXT("ntdll.dll"));
> f = _GLOBL_ GetProcAddress( hm, "vDbgPrintEx" );
> if( !f ) return;
> memcpy( &f_vDbgPrintEx, &f, sizeof(f) );
> }
>
> va_start( arglist, Fmt );
> n = f_vDbgPrintEx( DPFLTR_IHVDRIVER_ID, DPFLTR_ERROR_LEVEL, Fmt,
> arglist ); va_end( arglist );
> }
>
> ~~~~~~~~~~ cut here ~~~~~~~~


From: Ben Voigt [C++ MVP] on 5 Sep 2008 10:32
Doron Holan [MSFT] wrote:
> WHQL is not a 100% measure of quality across an entire driver, rather
> it is a set of tests specifically designed to test very specific
> parts of a driver. why is msft reponsible for the crud that FTDI
> wrote? serenum and sermouse work as expected on the in box version
> of serial, it correctly enforces exclusivity to the port

WHQL is realistically not going to be able to catch all bugs before
shipment, so maybe the answer is for WHQL signing to require a commitment
from the driver developer to participate in the BSOD crash dump program and
issue timely bug fixes (this is usually what is meant by having a "quality"
process in sw development, right?). A public "Wall of BSOD Shame" listing
drivers with known bugs and no fix might also be worth considering. Yes
these things would not come free, but is it important to Microsoft to shed
the reputation for Windows being crash-prone?

>
> d
>
>
> "Ben Voigt [C++ MVP]" <rbv(a)nospam.nospam> wrote in message
> news:ORV1HEgDJHA.528(a)TK2MSFTNGP06.phx.gbl...
>> Doron Holan [MSFT] wrote:
>>> sermouse opens the underlying serial port just like an app does. are you
>>> seeing this with the in box serial.sys driver? or with a
>>> 3rd party driver like one for a usb->serial device?
>>
>> It's USB/serial converter, from FTDI (doesn't use communication
>> device class). Their driver is WHQL. I wouldn't doubt that their
>> driver is causing the problem since one version ago simply opening a
>> device on a multicore system was BSOD within 10 seconds. Which
>> doesn't totally absolve MS of responsibility. What's the good of
>> WHQL if even buggy drivers can be approved?
>>
>> serenum and sermouse are out-of-the-box XP as far as I can determine.
>>
>> I should be able to load the problem configuration in a kernel
>> debugger and have debug output from my userland application showing
>> the result of the device interface open. If someone could advise me
>> on how to enable tracing of serenum/sermouse or where to set a
>> breakpoint, I could determine the order of events definitively.
>>
>>>
>>>
>>> "Ben Voigt [C++ MVP]" <rbv(a)nospam.nospam> wrote in message
>>> news:O7l7AheDJHA.2292(a)TK2MSFTNGP02.phx.gbl...
>>>> Doron Holan [MSFT] wrote:
>>>>> for serial mouse detection, there is a window between detection
>>>>> and driver load. serenum opens the port, detects the device,
>>>>> closes the port and then enumerates the child device. the child
>>>>> device stack will then attempt to open the port again. in
>>>>> between the serenum close and the child stack open, your app can
>>>>> easily open the port. if you do open the port in this window, the
>>>>> serial mouse driver will fail to open the port and fail the pnp
>>>>> start
>>>>
>>>> What I observed was:
>>>>
>>>> My application had an open handle to the port.
>>>>
>>>> AND
>>>>
>>>> The serial mouse driver was spamming my system with pointer motion
>>>> and mouse clicks.
>>>>
>>>> I cannot tell you with certainty which opened the port first, I
>>>> just understand that it should not be possible for both sermouse
>>>> and a user-mode application to have the port open no matter which
>>>> goes first. My application opened the port using the device interface
>>>> path received through WM_DEVICECHANGE and SetupDi* queries. Is
>>>> there any chance that the way file sharing and exclusivity is
>>>> enforced might this and the DosDevices link these as separate?
>>>> Although, I should think that serenum and sermouse should also use
>>>> the raw interface path.
>>>>>
>>>>> d
>>>>>
>>>>>
>>>>> "Ben Voigt [C++ MVP]" <rbv(a)nospam.nospam> wrote in message
>>>>> news:eGpGZ4VCJHA.2480(a)TK2MSFTNGP02.phx.gbl...
>>>>>>
>>>>>>
>>>>>> "Doron Holan [MSFT]" <doronh(a)online.microsoft.com> wrote in
>>>>>> message news:#erdV4SCJHA.2060(a)TK2MSFTNGP05.phx.gbl...
>>>>>>> i agree with chris, i have never heard of this happening
>>>>>>
>>>>>> I don't remember for sure, but I think I observed this behavior
>>>>>> fairly frequently when the device was surprise removed and
>>>>>> reinserted (i.e. bus reset) all before WM_DEVICECHANGE processing
>>>>>> for the original insertion completed.
>>>>>>
>>>>>> Of course, it could be the communication protocol with the device
>>>>>> itself broke down and never reached the ready state. There's a
>>>>>> lot of additional testing needed on the system.
>>>>>>
>>>>>> I am quite sure about the mouse issue though. I was able to
>>>>>> open a handle to the com port and Windows also decided to detect
>>>>>> a mouse. This shouldn't be possible, either Windows should
>>>>>> detect the mouse first and my CreateFile fails or else my
>>>>>> CreateFile succeeds first and then SERENUM can't listen for data
>>>>>> to run its heuristic mouse detection. There's another problem
>>>>>> where disabling the device in the WM_DEVICECHANGE handler
>>>>>> reliably and reproducibly shuts down the entire Windows Device
>>>>>> Manager / Plug and Play system. (This was one attempted
>>>>>> workaround for the aforementioned false mouse detection). This
>>>>>> is why I say WM_DEVICECHANGE isn't a 100% reliable method for
>>>>>> determining when the device is ready for use.
>>>>>>
>>>>>>>
>>>>>>> d
>>>>>>>
>>>>>>> --
>>>>>>> Please do not send e-mail directly to this alias. this alias is
>>>>>>> for newsgroup purposes only.
>>>>>>> This posting is provided "AS IS" with no warranties, and confers
>>>>>>> no rights.
>>>>>>>
>>>>>>>
>>>>>>> <chris.aseltine(a)gmail.com> wrote in message
>>>>>>> news:1cc364ba-649e-4bae-b37b-925de49852a9(a)c65g2000hsa.googlegroups.com...
>>>>>>>> On Aug 28, 8:13 am, "Ben Voigt [C++ MVP]" <r...(a)nospam.nospam>
>>>>>>>> wrote:
>>>>>>>>> Next, WM_DEVICECHANGE is quite unreliable. It is necessary to
>>>>>>>>> also poll the
>>>>>>>>> list of ports (of course using SetupDi* functions, not
>>>>>>>>> registry access, and
>>>>>>>>> test the device state) because the user-mode WM_DEVICECHANGE
>>>>>>>>> handler needs
>>>>>>>>> an arbitrary amount of time to complete (by definition,
>>>>>>>>> user-mode processes
>>>>>>>>> can be blocked by higher-priority user or kernel tasks) and
>>>>>>>>> some device insertion notifications are not delivered in this
>>>>>>>>> case.
>>>>>>>>
>>>>>>>> I've never heard of or observed this phenomenon, and your
>>>>>>>> explanation for why you think it happens is nebulous at best. Do
>>>>>>>> you have a reproducible example?


From: Doron Holan [MSFT] on 5 Sep 2008 17:23
a wall of shame is not practical. by getting signed, the vendor does get a
clear window into their OCA/bluescreen data that we collect. it is up to
the vendor to look the collected data.

d

--
Please do not send e-mail directly to this alias. this alias is for
newsgroup purposes only.
This posting is provided "AS IS" with no warranties, and confers no rights.


"Ben Voigt [C++ MVP]" <rbv(a)nospam.nospam> wrote in message
news:O51M9N2DJHA.3396(a)TK2MSFTNGP03.phx.gbl...
> Doron Holan [MSFT] wrote:
>> WHQL is not a 100% measure of quality across an entire driver, rather
>> it is a set of tests specifically designed to test very specific
>> parts of a driver. why is msft reponsible for the crud that FTDI
>> wrote? serenum and sermouse work as expected on the in box version
>> of serial, it correctly enforces exclusivity to the port
>
> WHQL is realistically not going to be able to catch all bugs before
> shipment, so maybe the answer is for WHQL signing to require a commitment
> from the driver developer to participate in the BSOD crash dump program
> and issue timely bug fixes (this is usually what is meant by having a
> "quality" process in sw development, right?). A public "Wall of BSOD
> Shame" listing drivers with known bugs and no fix might also be worth
> considering. Yes these things would not come free, but is it important to
> Microsoft to shed the reputation for Windows being crash-prone?
>
>>
>> d
>>
>>
>> "Ben Voigt [C++ MVP]" <rbv(a)nospam.nospam> wrote in message
>> news:ORV1HEgDJHA.528(a)TK2MSFTNGP06.phx.gbl...
>>> Doron Holan [MSFT] wrote:
>>>> sermouse opens the underlying serial port just like an app does. are
>>>> you seeing this with the in box serial.sys driver? or with a
>>>> 3rd party driver like one for a usb->serial device?
>>>
>>> It's USB/serial converter, from FTDI (doesn't use communication
>>> device class). Their driver is WHQL. I wouldn't doubt that their
>>> driver is causing the problem since one version ago simply opening a
>>> device on a multicore system was BSOD within 10 seconds. Which
>>> doesn't totally absolve MS of responsibility. What's the good of
>>> WHQL if even buggy drivers can be approved?
>>>
>>> serenum and sermouse are out-of-the-box XP as far as I can determine.
>>>
>>> I should be able to load the problem configuration in a kernel
>>> debugger and have debug output from my userland application showing
>>> the result of the device interface open. If someone could advise me
>>> on how to enable tracing of serenum/sermouse or where to set a
>>> breakpoint, I could determine the order of events definitively.
>>>
>>>>
>>>>
>>>> "Ben Voigt [C++ MVP]" <rbv(a)nospam.nospam> wrote in message
>>>> news:O7l7AheDJHA.2292(a)TK2MSFTNGP02.phx.gbl...
>>>>> Doron Holan [MSFT] wrote:
>>>>>> for serial mouse detection, there is a window between detection
>>>>>> and driver load. serenum opens the port, detects the device,
>>>>>> closes the port and then enumerates the child device. the child
>>>>>> device stack will then attempt to open the port again. in
>>>>>> between the serenum close and the child stack open, your app can
>>>>>> easily open the port. if you do open the port in this window, the
>>>>>> serial mouse driver will fail to open the port and fail the pnp
>>>>>> start
>>>>>
>>>>> What I observed was:
>>>>>
>>>>> My application had an open handle to the port.
>>>>>
>>>>> AND
>>>>>
>>>>> The serial mouse driver was spamming my system with pointer motion
>>>>> and mouse clicks.
>>>>>
>>>>> I cannot tell you with certainty which opened the port first, I
>>>>> just understand that it should not be possible for both sermouse
>>>>> and a user-mode application to have the port open no matter which
>>>>> goes first. My application opened the port using the device interface
>>>>> path received through WM_DEVICECHANGE and SetupDi* queries. Is
>>>>> there any chance that the way file sharing and exclusivity is
>>>>> enforced might this and the DosDevices link these as separate?
>>>>> Although, I should think that serenum and sermouse should also use
>>>>> the raw interface path.
>>>>>>
>>>>>> d
>>>>>>
>>>>>>
>>>>>> "Ben Voigt [C++ MVP]" <rbv(a)nospam.nospam> wrote in message
>>>>>> news:eGpGZ4VCJHA.2480(a)TK2MSFTNGP02.phx.gbl...
>>>>>>>
>>>>>>>
>>>>>>> "Doron Holan [MSFT]" <doronh(a)online.microsoft.com> wrote in
>>>>>>> message news:#erdV4SCJHA.2060(a)TK2MSFTNGP05.phx.gbl...
>>>>>>>> i agree with chris, i have never heard of this happening
>>>>>>>
>>>>>>> I don't remember for sure, but I think I observed this behavior
>>>>>>> fairly frequently when the device was surprise removed and
>>>>>>> reinserted (i.e. bus reset) all before WM_DEVICECHANGE processing
>>>>>>> for the original insertion completed.
>>>>>>>
>>>>>>> Of course, it could be the communication protocol with the device
>>>>>>> itself broke down and never reached the ready state. There's a
>>>>>>> lot of additional testing needed on the system.
>>>>>>>
>>>>>>> I am quite sure about the mouse issue though. I was able to
>>>>>>> open a handle to the com port and Windows also decided to detect
>>>>>>> a mouse. This shouldn't be possible, either Windows should
>>>>>>> detect the mouse first and my CreateFile fails or else my
>>>>>>> CreateFile succeeds first and then SERENUM can't listen for data
>>>>>>> to run its heuristic mouse detection. There's another problem
>>>>>>> where disabling the device in the WM_DEVICECHANGE handler
>>>>>>> reliably and reproducibly shuts down the entire Windows Device
>>>>>>> Manager / Plug and Play system. (This was one attempted
>>>>>>> workaround for the aforementioned false mouse detection). This
>>>>>>> is why I say WM_DEVICECHANGE isn't a 100% reliable method for
>>>>>>> determining when the device is ready for use.
>>>>>>>
>>>>>>>>
>>>>>>>> d
>>>>>>>>
>>>>>>>> --
>>>>>>>> Please do not send e-mail directly to this alias. this alias is
>>>>>>>> for newsgroup purposes only.
>>>>>>>> This posting is provided "AS IS" with no warranties, and confers
>>>>>>>> no rights.
>>>>>>>>
>>>>>>>>
>>>>>>>> <chris.aseltine(a)gmail.com> wrote in message
>>>>>>>> news:1cc364ba-649e-4bae-b37b-925de49852a9(a)c65g2000hsa.googlegroups.com...
>>>>>>>>> On Aug 28, 8:13 am, "Ben Voigt [C++ MVP]" <r...(a)nospam.nospam>
>>>>>>>>> wrote:
>>>>>>>>>> Next, WM_DEVICECHANGE is quite unreliable. It is necessary to
>>>>>>>>>> also poll the
>>>>>>>>>> list of ports (of course using SetupDi* functions, not
>>>>>>>>>> registry access, and
>>>>>>>>>> test the device state) because the user-mode WM_DEVICECHANGE
>>>>>>>>>> handler needs
>>>>>>>>>> an arbitrary amount of time to complete (by definition,
>>>>>>>>>> user-mode processes
>>>>>>>>>> can be blocked by higher-priority user or kernel tasks) and
>>>>>>>>>> some device insertion notifications are not delivered in this
>>>>>>>>>> case.
>>>>>>>>>
>>>>>>>>> I've never heard of or observed this phenomenon, and your
>>>>>>>>> explanation for why you think it happens is nebulous at best. Do
>>>>>>>>> you have a reproducible example?
>
>

From: Ben Voigt [C++ MVP] on 5 Sep 2008 17:49
Doron Holan [MSFT] wrote:
> a wall of shame is not practical. by getting signed, the vendor does
> get a clear window into their OCA/bluescreen data that we collect. it is
> up to the vendor to look the collected data.

Ok, but does the level to which they utilize that data and release fixes
influence approval of the next WHQL submission? That may be too hard to
judge, but at least making them certify that they have analyzed the
bluescreen data associated to their existing products might shock some
people into doing so.

Fixing bugs needs to be stated as mandatory and have the developer agree to
do it, regardless of the actual level of enforcement. Similarly vendors
need to be given a hard time if they fail to provide a driver compatible
with a new Windows version for products released in the last 3 years or
offered for sale in the last 12 months.

>
> d
>
>
> "Ben Voigt [C++ MVP]" <rbv(a)nospam.nospam> wrote in message
> news:O51M9N2DJHA.3396(a)TK2MSFTNGP03.phx.gbl...
>> Doron Holan [MSFT] wrote:
>>> WHQL is not a 100% measure of quality across an entire driver,
>>> rather it is a set of tests specifically designed to test very
>>> specific parts of a driver. why is msft reponsible for the crud
>>> that FTDI wrote? serenum and sermouse work as expected on the in
>>> box version of serial, it correctly enforces exclusivity to the port
>>
>> WHQL is realistically not going to be able to catch all bugs before
>> shipment, so maybe the answer is for WHQL signing to require a
>> commitment from the driver developer to participate in the BSOD
>> crash dump program and issue timely bug fixes (this is usually what
>> is meant by having a "quality" process in sw development, right?). A
>> public "Wall of BSOD Shame" listing drivers with known bugs and no
>> fix might also be worth considering. Yes these things would not
>> come free, but is it important to Microsoft to shed the reputation
>> for Windows being crash-prone?
>>>
>>> d
>>>
>>>
>>> "Ben Voigt [C++ MVP]" <rbv(a)nospam.nospam> wrote in message
>>> news:ORV1HEgDJHA.528(a)TK2MSFTNGP06.phx.gbl...
>>>> Doron Holan [MSFT] wrote:
>>>>> sermouse opens the underlying serial port just like an app does.
>>>>> are you seeing this with the in box serial.sys driver? or with a
>>>>> 3rd party driver like one for a usb->serial device?
>>>>
>>>> It's USB/serial converter, from FTDI (doesn't use communication
>>>> device class). Their driver is WHQL. I wouldn't doubt that their
>>>> driver is causing the problem since one version ago simply opening
>>>> a device on a multicore system was BSOD within 10 seconds. Which
>>>> doesn't totally absolve MS of responsibility. What's the good of
>>>> WHQL if even buggy drivers can be approved?
>>>>
>>>> serenum and sermouse are out-of-the-box XP as far as I can
>>>> determine. I should be able to load the problem configuration in a
>>>> kernel
>>>> debugger and have debug output from my userland application showing
>>>> the result of the device interface open. If someone could advise
>>>> me on how to enable tracing of serenum/sermouse or where to set a
>>>> breakpoint, I could determine the order of events definitively.
>>>>
>>>>>
>>>>>
>>>>> "Ben Voigt [C++ MVP]" <rbv(a)nospam.nospam> wrote in message
>>>>> news:O7l7AheDJHA.2292(a)TK2MSFTNGP02.phx.gbl...
>>>>>> Doron Holan [MSFT] wrote:
>>>>>>> for serial mouse detection, there is a window between detection
>>>>>>> and driver load. serenum opens the port, detects the device,
>>>>>>> closes the port and then enumerates the child device. the child
>>>>>>> device stack will then attempt to open the port again. in
>>>>>>> between the serenum close and the child stack open, your app can
>>>>>>> easily open the port. if you do open the port in this window,
>>>>>>> the serial mouse driver will fail to open the port and fail the
>>>>>>> pnp start
>>>>>>
>>>>>> What I observed was:
>>>>>>
>>>>>> My application had an open handle to the port.
>>>>>>
>>>>>> AND
>>>>>>
>>>>>> The serial mouse driver was spamming my system with pointer
>>>>>> motion and mouse clicks.
>>>>>>
>>>>>> I cannot tell you with certainty which opened the port first, I
>>>>>> just understand that it should not be possible for both sermouse
>>>>>> and a user-mode application to have the port open no matter which
>>>>>> goes first. My application opened the port using the device
>>>>>> interface path received through WM_DEVICECHANGE and SetupDi*
>>>>>> queries. Is there any chance that the way file sharing and
>>>>>> exclusivity is enforced might this and the DosDevices link these
>>>>>> as separate? Although, I should think that serenum and sermouse
>>>>>> should also use the raw interface path.
>>>>>>>
>>>>>>> d
>>>>>>>
>>>>>>>
>>>>>>> "Ben Voigt [C++ MVP]" <rbv(a)nospam.nospam> wrote in message
>>>>>>> news:eGpGZ4VCJHA.2480(a)TK2MSFTNGP02.phx.gbl...
>>>>>>>>
>>>>>>>>
>>>>>>>> "Doron Holan [MSFT]" <doronh(a)online.microsoft.com> wrote in
>>>>>>>> message news:#erdV4SCJHA.2060(a)TK2MSFTNGP05.phx.gbl...
>>>>>>>>> i agree with chris, i have never heard of this happening
>>>>>>>>
>>>>>>>> I don't remember for sure, but I think I observed this behavior
>>>>>>>> fairly frequently when the device was surprise removed and
>>>>>>>> reinserted (i.e. bus reset) all before WM_DEVICECHANGE
>>>>>>>> processing for the original insertion completed.
>>>>>>>>
>>>>>>>> Of course, it could be the communication protocol with the
>>>>>>>> device itself broke down and never reached the ready state. There's
>>>>>>>> a lot of additional testing needed on the system.
>>>>>>>>
>>>>>>>> I am quite sure about the mouse issue though. I was able to
>>>>>>>> open a handle to the com port and Windows also decided to
>>>>>>>> detect a mouse. This shouldn't be possible, either Windows
>>>>>>>> should detect the mouse first and my CreateFile fails or else
>>>>>>>> my CreateFile succeeds first and then SERENUM can't listen for
>>>>>>>> data to run its heuristic mouse detection. There's another
>>>>>>>> problem where disabling the device in the WM_DEVICECHANGE
>>>>>>>> handler reliably and reproducibly shuts down the entire
>>>>>>>> Windows Device Manager / Plug and Play system. (This was one
>>>>>>>> attempted workaround for the aforementioned false mouse
>>>>>>>> detection). This is why I say WM_DEVICECHANGE isn't a 100%
>>>>>>>> reliable method for determining when the device is ready for
>>>>>>>> use.
>>>>>>>>>
>>>>>>>>> d
>>>>>>>>>
>>>>>>>>> --
>>>>>>>>> Please do not send e-mail directly to this alias. this alias
>>>>>>>>> is for newsgroup purposes only.
>>>>>>>>> This posting is provided "AS IS" with no warranties, and
>>>>>>>>> confers no rights.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> <chris.aseltine(a)gmail.com> wrote in message
>>>>>>>>> news:1cc364ba-649e-4bae-b37b-925de49852a9(a)c65g2000hsa.googlegroups.com...
>>>>>>>>>> On Aug 28, 8:13 am, "Ben Voigt [C++ MVP]"
>>>>>>>>>> <r...(a)nospam.nospam> wrote:
>>>>>>>>>>> Next, WM_DEVICECHANGE is quite unreliable. It is necessary
>>>>>>>>>>> to also poll the
>>>>>>>>>>> list of ports (of course using SetupDi* functions, not
>>>>>>>>>>> registry access, and
>>>>>>>>>>> test the device state) because the user-mode WM_DEVICECHANGE
>>>>>>>>>>> handler needs
>>>>>>>>>>> an arbitrary amount of time to complete (by definition,
>>>>>>>>>>> user-mode processes
>>>>>>>>>>> can be blocked by higher-priority user or kernel tasks) and
>>>>>>>>>>> some device insertion notifications are not delivered in
>>>>>>>>>>> this case.
>>>>>>>>>>
>>>>>>>>>> I've never heard of or observed this phenomenon, and your
>>>>>>>>>> explanation for why you think it happens is nebulous at
>>>>>>>>>> best. Do you have a reproducible example?


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