Re: [ros-dev] serial.sys

[Alex Ionescu]

Rick Parrish wrote:
>   This email is directed mostly to Herve and anyone else
> familiar with 
>  SERIAL.SYS and how it works.
>  
>  Two years ago I implemented a small (5 kilobyte) WDM driver that 
>  "wrapped" SERIAL.SYS. It's an ugly hack that (almost) works. What I did 
>  was "hook" the interrupt service routine by directly modifying the IDT. 
>  It works most of the time but occassionally I get BSOD (and I don't know 
>  why).
>  
>  The driver installed ISR reads the MSR (modem status register) of the 
>  UART. The RDTSC instruction is used to generate a timestamp of when the 
>  MSR changed. Both pieces of data are stored in a FIFO - on every 
>  interrupt. A user mode program can later retrieve the information at 
>  regular time intervals.
>  
>  Hint: using the CTS, DCD, and DSR pins on a standard RS232 port, you can 
>  create a Poor Man's 3 Channel Logic Analyzer. Other applications include 
>  packet radio interface for amateur radio.
>  
>  What I'd like to do is merge the functionality directly into SERIAL.SYS 
>  (eg. work with the OS instead of around it). The extra functionality 
>  would be exposed through IOCTL or some other means but would not break 
>  ordinary serial COMM functionality.
>  
>  Disclaimer: I'm not a veteran author of kernel mode drivers.
>  
>  This is a relatively obscure application so if you want to reply 
>  off-list, that's perfectly fine by me.
>  
>  Here are my questions:
>  
>  1. how robust is the current SERIAL.SYS driver (I see a few "FIXME"s in 
>  the comments) ?
>  2. does ReactOS support or require code-signing of drivers? (probably 
>  not yet)
>  3. Can I run the "Genuine" Reactos SERIAL.SYS on "Genuine" Windows 
>  2K/XP? I think so (setting WFP aside). 4. is anyone in the ReactOS 
>  community interested in such a driver extension as described above? 
>  (probably not)
>  
>  Also, if anyone would like to see the logic analyzer program and related 
>  driver - please send me an email.
>  
>  Regards,
>  Rick
>  
>  _______________________________________________
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>  Ros-dev(a)reactos.org
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>   

Besides what Hervé wrote, have a look at Microsoft's serial.sys driver
in the WDK/DDK sample source code. It's the working driver used in XP+,
and you can easily modify it to test your changes on it.

-- 
Best regards,
Alex Ionescu
Project Lead, TinyKRNL
Kernel-Mode Software Design Engineer, ReactOS