xiaoxiang781216 commented on PR #10602:
URL: https://github.com/apache/nuttx/pull/10602#issuecomment-1719977191

   > > @patacongo I think @michallenc initial design may confuse you. stdio is 
a pure userspace library, the implementation of fopencookie or fmemopen doesn't 
need involve any kernel stuff: it's enough to add the 
callback(read/write/seek/close) to struct file_struct(FILE).
   > > So, I would suggest you read the manual from:
   > > https://pubs.opengroup.org/onlinepubs/9699919799/functions/fmemopen.html
   > > https://man7.org/linux/man-pages/man3/fopencookie.3.html
   > 
   > AFAIK that is not true. The user/supervisor mode is only one of several 
issues. I have enumerated many others below that this design pure user-space 
design will not handle. The bottom line: You cannot call from one task/process 
address space into another. 
   
   This case isn't suitable for stdio functions. How can you pass FILE * from 
one task/process to other task/process in kernel mode? It's impossible to 
happen in the first place.
   


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