[GitHub] [incubator-nuttx] xiaoxiang781216 commented on pull request #1120: fs/vfs/fs_stat.c: fill file size for mtd inode

[GitBox <gi...@apache.org>]

xiaoxiang781216 commented on pull request #1120:
URL: https://github.com/apache/incubator-nuttx/pull/1120#issuecomment-633786353


   > > Of course the approach with separate universal ioctl function returning underlying media size, as @patacongo suggested, will be much better.
   > 
   > According to the the things Xiang said, he is started some work on a mystery change. But my impression is that we should hide the character driver all together. If there were logic like this in inode_stat(), then I think we complete the illusion).
   
   Yes, I think it is a good idea to hide the proxy(bch and ftl) from user since we add the proxy transparently.
    
   > 
   > ```
   > type = inode type
   > size = 0;
   > 
   > if <type == character driver> then
   >     if <BIOC_GEOMETRY succeeds> then
   >         type = block driver
   >         calculate size
   >     else if <MTDIOC_GEOMETRY succeeeds them
   >         type = MTD driver
   >         calculate size
   >     endif
   >     Create the state buffer based on the type
   > endif
   > ```
   > 
   > That is a gross over-simplification, but I think we could use the ioctls to distinguish if a character driver if a proxy for a block or mtd driver, then hide the character driver altogether.
   
   The order need change like this:
   ```
   if <type == character driver> then
       if <MTDIOC_GEOMETRY succeeeds them
           type = MTD driver
           calculate size
       else if <BIOC_GEOMETRY succeeds> then
           type = block driver
           calculate size
       endif
       Create the state buffer based on the type
   endif
   ```
   since MTD proxy(FLT) implment BIOC_GEOMETRY too.


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