File caching

Hello,

We are building a device that captures data from a number of external
sources and organizes them for collection. The device connects to a PC
via USB.

Our device presents itself to the system as a FAT mass storage device.
The data is organized as a set of text files. The user would open the
files to see the current settings/data or could use our logging tool
which manages the periodic collection of the data if that is what they want.

Everything works pretty well except that the 'files' provided by the
device change without Windows knowledge of it. Since Windows appears to
cache the first image of the file we are not able to see the new values
without unmounting and remounting the device. This is obviously not
optimal. Everything works correctly when we mount it to Linux (which
does not cache the files or root directory).

Is there any adjustment we can make to our device that will allow it to
tell Windows not to cache anything regarding the filesystem...say,
during the device mounting process?

Thanks in advance,
Kevin

kwg
Mon Feb 14 19:26:50 CST 2005

Hello,

Windows will issue the TEST_UNIT_READY command to USB mass storage
devices that are defined as removable.

You can flag that the files on your device have changed with the
MEDIUM_HAS_CHANGED response code.

This will cause the OS to then refresh the volume.

Keith


Kevin wrote:
> Hello,
>
> We are building a device that captures data from a number of external

> sources and organizes them for collection. The device connects to a
PC
> via USB.
>
> Our device presents itself to the system as a FAT mass storage
device.
> The data is organized as a set of text files. The user would open
the
> files to see the current settings/data or could use our logging tool
> which manages the periodic collection of the data if that is what
they want.
>
> Everything works pretty well except that the 'files' provided by the
> device change without Windows knowledge of it. Since Windows appears
to
> cache the first image of the file we are not able to see the new
values
> without unmounting and remounting the device. This is obviously not
> optimal. Everything works correctly when we mount it to Linux (which

> does not cache the files or root directory).
>
> Is there any adjustment we can make to our device that will allow it
to
> tell Windows not to cache anything regarding the filesystem...say,
> during the device mounting process?
>
> Thanks in advance,
> Kevin

Maxim
Tue Feb 15 07:59:33 CST 2005

Open the files as noncached with FILE_FLAG_NO_BUFFERING.

--
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
maxim@storagecraft.com
http://www.storagecraft.com

"Kevin" <klm@morwood.ca> wrote in message
news:uOxrbjtEFHA.3200@TK2MSFTNGP10.phx.gbl...
> Hello,
>
> We are building a device that captures data from a number of external
> sources and organizes them for collection. The device connects to a PC
> via USB.
>
> Our device presents itself to the system as a FAT mass storage device.
> The data is organized as a set of text files. The user would open the
> files to see the current settings/data or could use our logging tool
> which manages the periodic collection of the data if that is what they want.
>
> Everything works pretty well except that the 'files' provided by the
> device change without Windows knowledge of it. Since Windows appears to
> cache the first image of the file we are not able to see the new values
> without unmounting and remounting the device. This is obviously not
> optimal. Everything works correctly when we mount it to Linux (which
> does not cache the files or root directory).
>
> Is there any adjustment we can make to our device that will allow it to
> tell Windows not to cache anything regarding the filesystem...say,
> during the device mounting process?
>
> Thanks in advance,
> Kevin