[PARPORT] PPA crashes and bugs (fwd)

From: Dr. Peter Cherriman (pjc@ecs.soton.ac.uk)
Date: Tue Jul 11 2000 - 08:48:54 EDT

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    I've found a fix to get the ppa driver to work with my new motherboard,
    however I be interested if people would see if the patch cause any noticable
    slow down in the transfer rate on their systems. This patch may also help
    other who are having problems with the ppa driver.

    Depending on the parallel port mode in the bios, the ppa driver in the 2.2.14
    kernel would crash on loading ppa, sd_mod or just fail to read the partition
    table. The same ppa.c is used in the latest 2.2.x kernel.

    I have tracked down, the problem, and it seems that since my parallel port is
    quite slow, a status bit is not alway set when it is expected to be in the
    driver. I fixed it by making a small change to ppa_wait() to check for both
    bit 6 and 7, which the current driver seems to assume will be set together,
    according to the comment in the ppa_wait() function. I also found I needed to
    call ppa_wait() from inside ppa_completion() to check both bits were set.

    I'd be grateful if people could try the patch, and measure the speed of file
    transfers with and without the patched module, rebooting between tests to
    clear an cache. I can get 22.1Mb/min in EPP mode (Mb=1024^2) with my
    motherboards parallel port.

    Perhaps this could be submitted as a kernel patch, or within a kernel config
    option if the performance hit is too great.

    Dr. Peter Cherriman       

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