2007/5/5, Alan Cox <[EMAIL PROTECTED]>: > On Sat, 5 May 2007 20:07:15 +0200 > Oliver Neukum <[EMAIL PROTECTED]> wrote: [cut] > > should I understand this so that, if tty_buffer_request_room() returns > > less than requested, the rest of the data should be dropped on the > > floor? > > If it returns NULL then either there is > 64K buffered (we can adjust > that if anyone shows need - its just for sanity) or the system is out of > RAM.
For my use case would be more sensible to accept the new data and discard the older one in the tty buffer: the tty buffer would be a moving window of the most recent incoming data. This because if someone does not read the incoming data maybe he's not interested in it. When he finally reads the data (assuming there was buffer underrun) he's likely interested to the more recent chunk of incoming data and not to an "head" of the data firstly received. Since I acquire measurement data from serial this make perfect sense for me. But does this make sense in general too? However, whatever policy the buffer uses, the fundamental point it's that when I flush the input buffer I should be sure that each byte read after the flush is *new* (current) data and not old one. This because when the input stream can be stopped I can check that there are 0 byte in the buffer, but when the stream can't be stopped I must use a flush-and-sleep (multiple times) heuristic before I can read a single *reliable* byte. > Alan > Regards, ~ Antonio ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Linux-usb-users@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
