[Linux-parport] hardware ECP reads

Mike Caplinger mc at msss.com
Wed Dec 14 12:37:47 EST 2005

After going through the process of recompiling the parport driver to
use ECP, I've discovered that seemingly even with all of the options
enabled (CONFIG_PARPORT_PC_FIFO, CONFIG_PARPORT_1284), ECP reads still
always go through the software emulation function in
parport_ieee1284_ecp_read_data, and are very very slow.

The key seems to be the fact that parport_pc_ecp_read_block_pio is
never called by the driver, as indicated by the comment "currently
broken, but working on it.. (FB)".

I'm doing the tests on RH 9 (kernel 2.4.20-8) but the code in the
latest 2.6 stable release ( appears to be the same.

Is this true, or am I confused?  Is the driver unable to do ECP
hardware reads?  If true it's unfortunate, since I was so looking to
be able to migrate all of my DOS ECP-reading applications over to
Linux.  One would be better off mapping the I/O ports and writing them
directly, making the parport driver fairly useless.

        Mike Caplinger, Malin Space Science Systems

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